GNAT Reference Manual
GNAT Reference Manual
GNAT Reference Manual
GNAT, The GNU Ada 95 Compiler
Version {No value for `gnat_version'}
Document revision level $Revision: 1.13.16.1 $
Date: $Date: 2004/06/09 09:20:43 $
Ada Core Technologies, Inc.
Copyright © 1995-2003, Free Software Foundation
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.1
or any later version published by the Free Software Foundation;
with the Invariant Sections being “GNU Free Documentation License”, with the
Front-Cover Texts being “GNAT Reference Manual”, and with no Back-Cover
Texts. A copy of the license is included in the section entitled “GNU
Free Documentation License”.
--- The Detailed Node Listing ---
About This Guide
Implementation Defined Pragmas
Implementation Defined Attributes
The Implementation of Standard I/O
The GNAT Library
Text_IO
Wide_Text_IO
Interfacing to Other Languages
Specialized Needs Annexes
Implementation of Specific Ada Features
Project File Reference
GNU Free Documentation License
Index
About This Guide
This manual contains useful information in writing programs using the
GNAT compiler. It includes information on implementation dependent
characteristics of GNAT, including all the information required by Annex
M of the standard.
Ada 95 is designed to be highly portable.
In general, a program will have the same effect even when compiled by
different compilers on different platforms.
However, since Ada 95 is designed to be used in a
wide variety of applications, it also contains a number of system
dependent features to be used in interfacing to the external world.
Note: Any program that makes use of implementation-dependent features
may be non-portable. You should follow good programming practice and
isolate and clearly document any sections of your program that make use
of these features in a non-portable manner.
What This Reference Manual Contains
This reference manual contains the following chapters:
This reference manual assumes that you are familiar with Ada 95
language, as described in the International Standard
ANSI/ISO/IEC-8652:1995, Jan 1995.
Conventions
Following are examples of the typographical and graphic conventions used
in this guide:
Functions, utility program names, standard names,
and classes.
Option flags
- File Names, button names, and field names.
Variables.
- Emphasis.
- [optional information or parameters]
- Examples are described by text
and then shown this way.
Commands that are entered by the user are preceded in this manual by the
characters $ (dollar sign followed by space). If your system uses this
sequence as a prompt, then the commands will appear exactly as you see them
in the manual. If your system uses some other prompt, then the command will
appear with the $ replaced by whatever prompt character you are using.
Related Information
See the following documents for further information on GNAT:
- GNAT User's Guide, which provides information on how to use
the GNAT compiler system.
- Ada 95 Reference Manual, which contains all reference
material for the Ada 95 programming language.
- Ada 95 Annotated Reference Manual, which is an annotated version
of the standard reference manual cited above. The annotations describe
detailed aspects of the design decision, and in particular contain useful
sections on Ada 83 compatibility.
- DEC Ada, Technical Overview and Comparison on DIGITAL Platforms,
which contains specific information on compatibility between GNAT and
DEC Ada 83 systems.
- DEC Ada, Language Reference Manual, part number AA-PYZAB-TK which
describes in detail the pragmas and attributes provided by the DEC Ada 83
compiler system.
1 Implementation Defined Pragmas
Ada 95 defines a set of pragmas that can be used to supply additional
information to the compiler. These language defined pragmas are
implemented in GNAT and work as described in the Ada 95 Reference
Manual.
In addition, Ada 95 allows implementations to define additional pragmas
whose meaning is defined by the implementation. GNAT provides a number
of these implementation-dependent pragmas which can be used to extend
and enhance the functionality of the compiler. This section of the GNAT
Reference Manual describes these additional pragmas.
Note that any program using these pragmas may not be portable to other
compilers (although GNAT implements this set of pragmas on all
platforms). Therefore if portability to other compilers is an important
consideration, the use of these pragmas should be minimized.
Pragma Abort_Defer
Syntax:
pragma Abort_Defer;
This pragma must appear at the start of the statement sequence of a
handled sequence of statements (right after the begin). It has
the effect of deferring aborts for the sequence of statements (but not
for the declarations or handlers, if any, associated with this statement
sequence).
Pragma Ada_83
Syntax:
pragma Ada_83;
A configuration pragma that establishes Ada 83 mode for the unit to
which it applies, regardless of the mode set by the command line
switches. In Ada 83 mode, GNAT attempts to be as compatible with
the syntax and semantics of Ada 83, as defined in the original Ada
83 Reference Manual as possible. In particular, the new Ada 95
keywords are not recognized, optional package bodies are allowed,
and generics may name types with unknown discriminants without using
the (<>) notation. In addition, some but not all of the additional
restrictions of Ada 83 are enforced.
Ada 83 mode is intended for two purposes. Firstly, it allows existing
legacy Ada 83 code to be compiled and adapted to GNAT with less effort.
Secondly, it aids in keeping code backwards compatible with Ada 83.
However, there is no guarantee that code that is processed correctly
by GNAT in Ada 83 mode will in fact compile and execute with an Ada
83 compiler, since GNAT does not enforce all the additional checks
required by Ada 83.
Pragma Ada_95
Syntax:
pragma Ada_95;
A configuration pragma that establishes Ada 95 mode for the unit to which
it applies, regardless of the mode set by the command line switches.
This mode is set automatically for the Ada and System
packages and their children, so you need not specify it in these
contexts. This pragma is useful when writing a reusable component that
itself uses Ada 95 features, but which is intended to be usable from
either Ada 83 or Ada 95 programs.
Pragma Annotate
Syntax:
pragma Annotate (IDENTIFIER {, ARG});
ARG ::= NAME | EXPRESSION
This pragma is used to annotate programs. identifier identifies
the type of annotation. GNAT verifies this is an identifier, but does
not otherwise analyze it. The arg argument
can be either a string literal or an
expression. String literals are assumed to be of type
Standard.String. Names of entities are simply analyzed as entity
names. All other expressions are analyzed as expressions, and must be
unambiguous.
The analyzed pragma is retained in the tree, but not otherwise processed
by any part of the GNAT compiler. This pragma is intended for use by
external tools, including ASIS.
Pragma Assert
Syntax:
pragma Assert (
boolean_EXPRESSION
[, static_string_EXPRESSION]);
The effect of this pragma depends on whether the corresponding command
line switch is set to activate assertions. The pragma expands into code
equivalent to the following:
if assertions-enabled then
if not boolean_EXPRESSION then
System.Assertions.Raise_Assert_Failure
(string_EXPRESSION);
end if;
end if;
The string argument, if given, is the message that will be associated
with the exception occurrence if the exception is raised. If no second
argument is given, the default message is file:nnn,
where file is the name of the source file containing the assert,
and nnn is the line number of the assert. A pragma is not a
statement, so if a statement sequence contains nothing but a pragma
assert, then a null statement is required in addition, as in:
...
if J > 3 then
pragma Assert (K > 3, "Bad value for K");
null;
end if;
Note that, as with the if statement to which it is equivalent, the
type of the expression is either Standard.Boolean, or any type derived
from this standard type.
If assertions are disabled (switch -gnata not used), then there
is no effect (and in particular, any side effects from the expression
are suppressed). More precisely it is not quite true that the pragma
has no effect, since the expression is analyzed, and may cause types
to be frozen if they are mentioned here for the first time.
If assertions are enabled, then the given expression is tested, and if
it is False then System.Assertions.Raise_Assert_Failure is called
which results in the raising of Assert_Failure with the given message.
If the boolean expression has side effects, these side effects will turn
on and off with the setting of the assertions mode, resulting in
assertions that have an effect on the program. You should generally
avoid side effects in the expression arguments of this pragma. However,
the expressions are analyzed for semantic correctness whether or not
assertions are enabled, so turning assertions on and off cannot affect
the legality of a program.
Pragma Ast_Entry
Syntax:
pragma AST_Entry (entry_IDENTIFIER);
This pragma is implemented only in the OpenVMS implementation of GNAT. The
argument is the simple name of a single entry; at most one AST_Entry
pragma is allowed for any given entry. This pragma must be used in
conjunction with the AST_Entry attribute, and is only allowed after
the entry declaration and in the same task type specification or single task
as the entry to which it applies. This pragma specifies that the given entry
may be used to handle an OpenVMS asynchronous system trap (AST)
resulting from an OpenVMS system service call. The pragma does not affect
normal use of the entry. For further details on this pragma, see the
DEC Ada Language Reference Manual, section 9.12a.
Pragma C_Pass_By_Copy
Syntax:
pragma C_Pass_By_Copy
([Max_Size =>] static_integer_EXPRESSION);
Normally the default mechanism for passing C convention records to C
convention subprograms is to pass them by reference, as suggested by RM
B.3(69). Use the configuration pragma C_Pass_By_Copy to change
this default, by requiring that record formal parameters be passed by
copy if all of the following conditions are met:
- The size of the record type does not exceed
static_integer_expression.
- The record type has
Convention C.
- The formal parameter has this record type, and the subprogram has a
foreign (non-Ada) convention.
If these conditions are met the argument is passed by copy, i.e. in a
manner consistent with what C expects if the corresponding formal in the
C prototype is a struct (rather than a pointer to a struct).
You can also pass records by copy by specifying the convention
C_Pass_By_Copy for the record type, or by using the extended
Import and Export pragmas, which allow specification of
passing mechanisms on a parameter by parameter basis.
Pragma Comment
Syntax:
pragma Comment (static_string_EXPRESSION);
This is almost identical in effect to pragma Ident. It allows the
placement of a comment into the object file and hence into the
executable file if the operating system permits such usage. The
difference is that Comment, unlike Ident, has
no limitations on placement of the pragma (it can be placed
anywhere in the main source unit), and if more than one pragma
is used, all comments are retained.
Pragma Common_Object
Syntax:
pragma Common_Object (
[Internal =>] LOCAL_NAME,
[, [External =>] EXTERNAL_SYMBOL]
[, [Size =>] EXTERNAL_SYMBOL] );
EXTERNAL_SYMBOL ::=
IDENTIFIER
| static_string_EXPRESSION
This pragma enables the shared use of variables stored in overlaid
linker areas corresponding to the use of COMMON
in Fortran. The single
object local_name is assigned to the area designated by
the External argument.
You may define a record to correspond to a series
of fields. The size argument
is syntax checked in GNAT, but otherwise ignored.
Common_Object is not supported on all platforms. If no
support is available, then the code generator will issue a message
indicating that the necessary attribute for implementation of this
pragma is not available.
Pragma Compile_Time_Warning
Syntax:
pragma Compile_Time_Warning
(boolean_EXPRESSION, static_string_EXPRESSION);
This pragma can be used to generate additional compile time warnings. It
is particularly useful in generics, where warnings can be issued for
specific problematic instantiations. The first parameter is a boolean
expression. The pragma is effective only if the value of this expression
is known at compile time, and has the value True. The set of expressions
whose values are known at compile time includes all static boolean
expressions, and also other values which the compiler can determine
at compile time (e.g. the size of a record type set by an explicit
size representation clause, or the value of a variable which was
initialized to a constant and is known not to have been modified).
If these conditions are met, a warning message is generated using
the value given as the second argument. This string value may contain
embedded ASCII.LF characters to break the message into multiple lines.
Pragma Complex_Representation
Syntax:
pragma Complex_Representation
([Entity =>] LOCAL_NAME);
The Entity argument must be the name of a record type which has
two fields of the same floating-point type. The effect of this pragma is
to force gcc to use the special internal complex representation form for
this record, which may be more efficient. Note that this may result in
the code for this type not conforming to standard ABI (application
binary interface) requirements for the handling of record types. For
example, in some environments, there is a requirement for passing
records by pointer, and the use of this pragma may result in passing
this type in floating-point registers.
Pragma Component_Alignment
Syntax:
pragma Component_Alignment (
[Form =>] ALIGNMENT_CHOICE
[, [Name =>] type_LOCAL_NAME]);
ALIGNMENT_CHOICE ::=
Component_Size
| Component_Size_4
| Storage_Unit
| Default
Specifies the alignment of components in array or record types.
The meaning of the Form argument is as follows:
Component_Size- Aligns scalar components and subcomponents of the array or record type
on boundaries appropriate to their inherent size (naturally
aligned). For example, 1-byte components are aligned on byte boundaries,
2-byte integer components are aligned on 2-byte boundaries, 4-byte
integer components are aligned on 4-byte boundaries and so on. These
alignment rules correspond to the normal rules for C compilers on all
machines except the VAX.
Component_Size_4- Naturally aligns components with a size of four or fewer
bytes. Components that are larger than 4 bytes are placed on the next
4-byte boundary.
Storage_Unit- Specifies that array or record components are byte aligned, i.e.
aligned on boundaries determined by the value of the constant
System.Storage_Unit.
Default- Specifies that array or record components are aligned on default
boundaries, appropriate to the underlying hardware or operating system or
both. For OpenVMS VAX systems, the
Default choice is the same as
the Storage_Unit choice (byte alignment). For all other systems,
the Default choice is the same as Component_Size (natural
alignment).
If the Name parameter is present, type_local_name must
refer to a local record or array type, and the specified alignment
choice applies to the specified type. The use of
Component_Alignment together with a pragma Pack causes the
Component_Alignment pragma to be ignored. The use of
Component_Alignment together with a record representation clause
is only effective for fields not specified by the representation clause.
If the Name parameter is absent, the pragma can be used as either
a configuration pragma, in which case it applies to one or more units in
accordance with the normal rules for configuration pragmas, or it can be
used within a declarative part, in which case it applies to types that
are declared within this declarative part, or within any nested scope
within this declarative part. In either case it specifies the alignment
to be applied to any record or array type which has otherwise standard
representation.
If the alignment for a record or array type is not specified (using
pragma Pack, pragma Component_Alignment, or a record rep
clause), the GNAT uses the default alignment as described previously.
Pragma Convention_Identifier
Syntax:
pragma Convention_Identifier (
[Name =>] IDENTIFIER,
[Convention =>] convention_IDENTIFIER);
This pragma provides a mechanism for supplying synonyms for existing
convention identifiers. The Name identifier can subsequently
be used as a synonym for the given convention in other pragmas (including
for example pragma Import or another Convention_Identifier
pragma). As an example of the use of this, suppose you had legacy code
which used Fortran77 as the identifier for Fortran. Then the pragma:
pragma Convention_Indentifier (Fortran77, Fortran);
would allow the use of the convention identifier Fortran77 in
subsequent code, avoiding the need to modify the sources. As another
example, you could use this to parametrize convention requirements
according to systems. Suppose you needed to use Stdcall on
windows systems, and C on some other system, then you could
define a convention identifier Library and use a single
Convention_Identifier pragma to specify which convention
would be used system-wide.
Pragma CPP_Class
Syntax:
pragma CPP_Class ([Entity =>] LOCAL_NAME);
The argument denotes an entity in the current declarative region
that is declared as a tagged or untagged record type. It indicates that
the type corresponds to an externally declared C++ class type, and is to
be laid out the same way that C++ would lay out the type.
If (and only if) the type is tagged, at least one component in the
record must be of type Interfaces.CPP.Vtable_Ptr, corresponding
to the C++ Vtable (or Vtables in the case of multiple inheritance) used
for dispatching.
Types for which CPP_Class is specified do not have assignment or
equality operators defined (such operations can be imported or declared
as subprograms as required). Initialization is allowed only by
constructor functions (see pragma CPP_Constructor).
Pragma CPP_Class is intended primarily for automatic generation
using an automatic binding generator tool.
See Interfacing to C++ for related information.
Pragma CPP_Constructor
Syntax:
pragma CPP_Constructor ([Entity =>] LOCAL_NAME);
This pragma identifies an imported function (imported in the usual way
with pragma Import) as corresponding to a C++
constructor. The argument is a name that must have been
previously mentioned in a pragma Import
with Convention = CPP, and must be of one of the following
forms:
function Fname return T'Class
function Fname (...) return T'Class
where T is a tagged type to which the pragma CPP_Class applies.
The first form is the default constructor, used when an object of type
T is created on the Ada side with no explicit constructor. Other
constructors (including the copy constructor, which is simply a special
case of the second form in which the one and only argument is of type
T), can only appear in two contexts:
- On the right side of an initialization of an object of type T.
- In an extension aggregate for an object of a type derived from T.
Although the constructor is described as a function that returns a value
on the Ada side, it is typically a procedure with an extra implicit
argument (the object being initialized) at the implementation
level. GNAT issues the appropriate call, whatever it is, to get the
object properly initialized.
In the case of derived objects, you may use one of two possible forms
for declaring and creating an object:
New_Object : Derived_T
New_Object : Derived_T := (constructor-call with ...)
In the first case the default constructor is called and extension fields
if any are initialized according to the default initialization
expressions in the Ada declaration. In the second case, the given
constructor is called and the extension aggregate indicates the explicit
values of the extension fields.
If no constructors are imported, it is impossible to create any objects
on the Ada side. If no default constructor is imported, only the
initialization forms using an explicit call to a constructor are
permitted.
Pragma CPP_Constructor is intended primarily for automatic generation
using an automatic binding generator tool.
See Interfacing to C++ for more related information.
Pragma CPP_Virtual
Syntax:
pragma CPP_Virtual
[Entity =>] ENTITY,
[, [Vtable_Ptr =>] vtable_ENTITY,]
[, [Position =>] static_integer_EXPRESSION]);
This pragma serves the same function as pragma Import in that
case of a virtual function imported from C++. The Entity argument
must be a
primitive subprogram of a tagged type to which pragma CPP_Class
applies. The Vtable_Ptr argument specifies
the Vtable_Ptr component which contains the
entry for this virtual function. The Position argument
is the sequential number
counting virtual functions for this Vtable starting at 1.
The Vtable_Ptr and Position arguments may be omitted if
there is one Vtable_Ptr present (single inheritance case) and all
virtual functions are imported. In that case the compiler can deduce both
these values.
No External_Name or Link_Name arguments are required for a
virtual function, since it is always accessed indirectly via the
appropriate Vtable entry.
Pragma CPP_Virtual is intended primarily for automatic generation
using an automatic binding generator tool.
See Interfacing to C++ for related information.
Pragma CPP_Vtable
Syntax:
pragma CPP_Vtable (
[Entity =>] ENTITY,
[Vtable_Ptr =>] vtable_ENTITY,
[Entry_Count =>] static_integer_EXPRESSION);
Given a record to which the pragma CPP_Class applies,
this pragma can be specified for each component of type
CPP.Interfaces.Vtable_Ptr.
Entity is the tagged type, Vtable_Ptr
is the record field of type Vtable_Ptr, and Entry_Count is
the number of virtual functions on the C++ side. Not all of these
functions need to be imported on the Ada side.
You may omit the CPP_Vtable pragma if there is only one
Vtable_Ptr component in the record and all virtual functions are
imported on the Ada side (the default value for the entry count in this
case is simply the total number of virtual functions).
Pragma CPP_Vtable is intended primarily for automatic generation
using an automatic binding generator tool.
See Interfacing to C++ for related information.
Pragma Debug
Syntax:
pragma Debug (PROCEDURE_CALL_WITHOUT_SEMICOLON);
PROCEDURE_CALL_WITHOUT_SEMICOLON ::=
PROCEDURE_NAME
| PROCEDURE_PREFIX ACTUAL_PARAMETER_PART
The argument has the syntactic form of an expression, meeting the
syntactic requirements for pragmas.
If assertions are not enabled on the command line, this pragma has no
effect. If asserts are enabled, the semantics of the pragma is exactly
equivalent to the procedure call statement corresponding to the argument
with a terminating semicolon. Pragmas are permitted in sequences of
declarations, so you can use pragma Debug to intersperse calls to
debug procedures in the middle of declarations.
Pragma Elaboration_Checks
Syntax:
pragma Elaboration_Checks (RM | Static);
This is a configuration pragma that provides control over the
elaboration model used by the compilation affected by the
pragma. If the parameter is RM, then the dynamic elaboration
model described in the Ada Reference Manual is used, as though
the -gnatE switch had been specified on the command
line. If the parameter is Static, then the default GNAT static
model is used. This configuration pragma overrides the setting
of the command line. For full details on the elaboration models
used by the GNAT compiler, see section “Elaboration Order
Handling in GNAT” in the GNAT User's Guide.
Pragma Eliminate
Syntax:
pragma Eliminate (
[Unit_Name =>] IDENTIFIER |
SELECTED_COMPONENT);
pragma Eliminate (
[Unit_Name =>] IDENTIFIER |
SELECTED_COMPONENT,
[Entity =>] IDENTIFIER |
SELECTED_COMPONENT |
STRING_LITERAL
[,[Parameter_Types =>] PARAMETER_TYPES]
[,[Result_Type =>] result_SUBTYPE_NAME]
[,[Homonym_Number =>] INTEGER_LITERAL]);
PARAMETER_TYPES ::= (SUBTYPE_NAME {, SUBTYPE_NAME})
SUBTYPE_NAME ::= STRING_LITERAL
This pragma indicates that the given entity is not used outside the
compilation unit it is defined in. The entity may be either a subprogram
or a variable.
If the entity to be eliminated is a library level subprogram, then
the first form of pragma Eliminate is used with only a single argument.
In this form, the Unit_Name argument specifies the name of the
library level unit to be eliminated.
In all other cases, both Unit_Name and Entity arguments
are required. If item is an entity of a library package, then the first
argument specifies the unit name, and the second argument specifies
the particular entity. If the second argument is in string form, it must
correspond to the internal manner in which GNAT stores entity names (see
compilation unit Namet in the compiler sources for details).
The remaining parameters are optionally used to distinguish
between overloaded subprograms. There are two ways of doing this.
Use Parameter_Types and Result_Type to specify the
profile of the subprogram to be eliminated in a manner similar to that
used for
the extended Import and Export pragmas, except that the
subtype names are always given as string literals, again corresponding
to the internal manner in which GNAT stores entity names.
Alternatively, the Homonym_Number parameter is used to specify
which overloaded alternative is to be eliminated. A value of 1 indicates
the first subprogram (in lexical order), 2 indicates the second etc.
The effect of the pragma is to allow the compiler to eliminate
the code or data associated with the named entity. Any reference to
an eliminated entity outside the compilation unit it is defined in,
causes a compile time or link time error.
The parameters of this pragma may be given in any order, as long as
the usual rules for use of named parameters and position parameters
are used.
The intention of pragma Eliminate is to allow a program to be compiled
in a system independent manner, with unused entities eliminated, without
the requirement of modifying the source text. Normally the required set
of Eliminate pragmas is constructed automatically using the gnatelim
tool. Elimination of unused entities local to a compilation unit is
automatic, without requiring the use of pragma Eliminate.
Note that the reason this pragma takes string literals where names might
be expected is that a pragma Eliminate can appear in a context where the
relevant names are not visible.
Pragma Export_Exception
Syntax:
pragma Export_Exception (
[Internal =>] LOCAL_NAME,
[, [External =>] EXTERNAL_SYMBOL,]
[, [Form =>] Ada | VMS]
[, [Code =>] static_integer_EXPRESSION]);
EXTERNAL_SYMBOL ::=
IDENTIFIER
| static_string_EXPRESSION
This pragma is implemented only in the OpenVMS implementation of GNAT. It
causes the specified exception to be propagated outside of the Ada program,
so that it can be handled by programs written in other OpenVMS languages.
This pragma establishes an external name for an Ada exception and makes the
name available to the OpenVMS Linker as a global symbol. For further details
on this pragma, see the
DEC Ada Language Reference Manual, section 13.9a3.2.
Pragma Export_Function
Syntax:
pragma Export_Function (
[Internal =>] LOCAL_NAME,
[, [External =>] EXTERNAL_SYMBOL]
[, [Parameter_Types =>] PARAMETER_TYPES]
[, [Result_Type =>] result_SUBTYPE_MARK]
[, [Mechanism =>] MECHANISM]
[, [Result_Mechanism =>] MECHANISM_NAME]);
EXTERNAL_SYMBOL ::=
IDENTIFIER
| static_string_EXPRESSION
| ""
PARAMETER_TYPES ::=
null
| TYPE_DESIGNATOR {, TYPE_DESIGNATOR}
TYPE_DESIGNATOR ::=
subtype_NAME
| subtype_Name ' Access
MECHANISM ::=
MECHANISM_NAME
| (MECHANISM_ASSOCIATION {, MECHANISM_ASSOCIATION})
MECHANISM_ASSOCIATION ::=
[formal_parameter_NAME =>] MECHANISM_NAME
MECHANISM_NAME ::=
Value
| Reference
Use this pragma to make a function externally callable and optionally
provide information on mechanisms to be used for passing parameter and
result values. We recommend, for the purposes of improving portability,
this pragma always be used in conjunction with a separate pragma
Export, which must precede the pragma Export_Function.
GNAT does not require a separate pragma Export, but if none is
present, Convention Ada is assumed, which is usually
not what is wanted, so it is usually appropriate to use this
pragma in conjunction with a Export or Convention
pragma that specifies the desired foreign convention.
Pragma Export_Function
(and Export, if present) must appear in the same declarative
region as the function to which they apply.
internal_name must uniquely designate the function to which the
pragma applies. If more than one function name exists of this name in
the declarative part you must use the Parameter_Types and
Result_Type parameters is mandatory to achieve the required
unique designation. subtype_ marks in these parameters must
exactly match the subtypes in the corresponding function specification,
using positional notation to match parameters with subtype marks.
The form with an 'Access attribute can be used to match an
anonymous access parameter.
Note that passing by descriptor is not supported, even on the OpenVMS
ports of GNAT.
Special treatment is given if the EXTERNAL is an explicit null
string or a static string expressions that evaluates to the null
string. In this case, no external name is generated. This form
still allows the specification of parameter mechanisms.
Pragma Export_Object
Syntax:
pragma Export_Object
[Internal =>] LOCAL_NAME,
[, [External =>] EXTERNAL_SYMBOL]
[, [Size =>] EXTERNAL_SYMBOL]
EXTERNAL_SYMBOL ::=
IDENTIFIER
| static_string_EXPRESSION
This pragma designates an object as exported, and apart from the
extended rules for external symbols, is identical in effect to the use of
the normal Export pragma applied to an object. You may use a
separate Export pragma (and you probably should from the point of view
of portability), but it is not required. Size is syntax checked,
but otherwise ignored by GNAT.
Pragma Export_Procedure
Syntax:
pragma Export_Procedure (
[Internal =>] LOCAL_NAME
[, [External =>] EXTERNAL_SYMBOL]
[, [Parameter_Types =>] PARAMETER_TYPES]
[, [Mechanism =>] MECHANISM]);
EXTERNAL_SYMBOL ::=
IDENTIFIER
| static_string_EXPRESSION
| ""
PARAMETER_TYPES ::=
null
| TYPE_DESIGNATOR {, TYPE_DESIGNATOR}
TYPE_DESIGNATOR ::=
subtype_NAME
| subtype_Name ' Access
MECHANISM ::=
MECHANISM_NAME
| (MECHANISM_ASSOCIATION {, MECHANISM_ASSOCIATION})
MECHANISM_ASSOCIATION ::=
[formal_parameter_NAME =>] MECHANISM_NAME
MECHANISM_NAME ::=
Value
| Reference
This pragma is identical to Export_Function except that it
applies to a procedure rather than a function and the parameters
Result_Type and Result_Mechanism are not permitted.
GNAT does not require a separate pragma Export, but if none is
present, Convention Ada is assumed, which is usually
not what is wanted, so it is usually appropriate to use this
pragma in conjunction with a Export or Convention
pragma that specifies the desired foreign convention.
Note that passing by descriptor is not supported, even on the OpenVMS
ports of GNAT.
Special treatment is given if the EXTERNAL is an explicit null
string or a static string expressions that evaluates to the null
string. In this case, no external name is generated. This form
still allows the specification of parameter mechanisms.
Pragma Export_Value
Syntax:
pragma Export_Value (
[Value =>] static_integer_EXPRESSION,
[Link_Name =>] static_string_EXPRESSION);
This pragma serves to export a static integer value for external use.
The first argument specifies the value to be exported. The Link_Name
argument specifies the symbolic name to be associated with the integer
value. This pragma is useful for defining a named static value in Ada
that can be referenced in assembly language units to be linked with
the application. This pragma is currently supported only for the
AAMP target and is ignored for other targets.
Pragma Export_Valued_Procedure
Syntax:
pragma Export_Valued_Procedure (
[Internal =>] LOCAL_NAME
[, [External =>] EXTERNAL_SYMBOL]
[, [Parameter_Types =>] PARAMETER_TYPES]
[, [Mechanism =>] MECHANISM]);
EXTERNAL_SYMBOL ::=
IDENTIFIER
| static_string_EXPRESSION
| ""
PARAMETER_TYPES ::=
null
| TYPE_DESIGNATOR {, TYPE_DESIGNATOR}
TYPE_DESIGNATOR ::=
subtype_NAME
| subtype_Name ' Access
MECHANISM ::=
MECHANISM_NAME
| (MECHANISM_ASSOCIATION {, MECHANISM_ASSOCIATION})
MECHANISM_ASSOCIATION ::=
[formal_parameter_NAME =>] MECHANISM_NAME
MECHANISM_NAME ::=
Value
| Reference
This pragma is identical to Export_Procedure except that the
first parameter of local_name, which must be present, must be of
mode OUT, and externally the subprogram is treated as a function
with this parameter as the result of the function. GNAT provides for
this capability to allow the use of OUT and IN OUT
parameters in interfacing to external functions (which are not permitted
in Ada functions).
GNAT does not require a separate pragma Export, but if none is
present, Convention Ada is assumed, which is almost certainly
not what is wanted since the whole point of this pragma is to interface
with foreign language functions, so it is usually appropriate to use this
pragma in conjunction with a Export or Convention
pragma that specifies the desired foreign convention.
Note that passing by descriptor is not supported, even on the OpenVMS
ports of GNAT.
Special treatment is given if the EXTERNAL is an explicit null
string or a static string expressions that evaluates to the null
string. In this case, no external name is generated. This form
still allows the specification of parameter mechanisms.
Pragma Extend_System
Syntax:
pragma Extend_System ([Name =>] IDENTIFIER);
This pragma is used to provide backwards compatibility with other
implementations that extend the facilities of package System. In
GNAT, System contains only the definitions that are present in
the Ada 95 RM. However, other implementations, notably the DEC Ada 83
implementation, provide many extensions to package System.
For each such implementation accommodated by this pragma, GNAT provides a
package Aux_xxx, e.g. Aux_DEC for the DEC Ada 83
implementation, which provides the required additional definitions. You
can use this package in two ways. You can with it in the normal
way and access entities either by selection or using a use
clause. In this case no special processing is required.
However, if existing code contains references such as
System.xxx where xxx is an entity in the extended
definitions provided in package System, you may use this pragma
to extend visibility in System in a non-standard way that
provides greater compatibility with the existing code. Pragma
Extend_System is a configuration pragma whose single argument is
the name of the package containing the extended definition
(e.g. Aux_DEC for the DEC Ada case). A unit compiled under
control of this pragma will be processed using special visibility
processing that looks in package System.Aux_xxx where
Aux_xxx is the pragma argument for any entity referenced in
package System, but not found in package System.
You can use this pragma either to access a predefined System
extension supplied with the compiler, for example Aux_DEC or
you can construct your own extension unit following the above
definition. Note that such a package is a child of System
and thus is considered part of the implementation. To compile
it you will have to use the appropriate switch for compiling
system units. See the GNAT User's Guide for details.
Pragma External
Syntax:
pragma External (
[ Convention =>] convention_IDENTIFIER,
[ Entity =>] local_NAME
[, [External_Name =>] static_string_EXPRESSION ]
[, [Link_Name =>] static_string_EXPRESSION ]);
This pragma is identical in syntax and semantics to pragma
Export as defined in the Ada Reference Manual. It is
provided for compatibility with some Ada 83 compilers that
used this pragma for exactly the same purposes as pragma
Export before the latter was standardized.
Pragma External_Name_Casing
Syntax:
pragma External_Name_Casing (
Uppercase | Lowercase
[, Uppercase | Lowercase | As_Is]);
This pragma provides control over the casing of external names associated
with Import and Export pragmas. There are two cases to consider:
- Implicit external names
- Implicit external names are derived from identifiers. The most common case
arises when a standard Ada 95 Import or Export pragma is used with only two
arguments, as in:
pragma Import (C, C_Routine);
Since Ada is a case insensitive language, the spelling of the identifier in
the Ada source program does not provide any information on the desired
casing of the external name, and so a convention is needed. In GNAT the
default treatment is that such names are converted to all lower case
letters. This corresponds to the normal C style in many environments.
The first argument of pragma External_Name_Casing can be used to
control this treatment. If Uppercase is specified, then the name
will be forced to all uppercase letters. If Lowercase is specified,
then the normal default of all lower case letters will be used.
This same implicit treatment is also used in the case of extended DEC Ada 83
compatible Import and Export pragmas where an external name is explicitly
specified using an identifier rather than a string.
- Explicit external names
- Explicit external names are given as string literals. The most common case
arises when a standard Ada 95 Import or Export pragma is used with three
arguments, as in:
pragma Import (C, C_Routine, "C_routine");
In this case, the string literal normally provides the exact casing required
for the external name. The second argument of pragma
External_Name_Casing may be used to modify this behavior.
If Uppercase is specified, then the name
will be forced to all uppercase letters. If Lowercase is specified,
then the name will be forced to all lowercase letters. A specification of
As_Is provides the normal default behavior in which the casing is
taken from the string provided.
This pragma may appear anywhere that a pragma is valid. In particular, it
can be used as a configuration pragma in the gnat.adc file, in which
case it applies to all subsequent compilations, or it can be used as a program
unit pragma, in which case it only applies to the current unit, or it can
be used more locally to control individual Import/Export pragmas.
It is primarily intended for use with OpenVMS systems, where many
compilers convert all symbols to upper case by default. For interfacing to
such compilers (e.g. the DEC C compiler), it may be convenient to use
the pragma:
pragma External_Name_Casing (Uppercase, Uppercase);
to enforce the upper casing of all external symbols.
Pragma Finalize_Storage_Only
Syntax:
pragma Finalize_Storage_Only (first_subtype_LOCAL_NAME);
This pragma allows the compiler not to emit a Finalize call for objects
defined at the library level. This is mostly useful for types where
finalization is only used to deal with storage reclamation since in most
environments it is not necessary to reclaim memory just before terminating
execution, hence the name.
Pragma Float_Representation
Syntax:
pragma Float_Representation (FLOAT_REP);
FLOAT_REP ::= VAX_Float | IEEE_Float
This pragma
allows control over the internal representation chosen for the predefined
floating point types declared in the packages Standard and
System. On all systems other than OpenVMS, the argument must
be IEEE_Float and the pragma has no effect. On OpenVMS, the
argument may be VAX_Float to specify the use of the VAX float
format for the floating-point types in Standard. This requires that
the standard runtime libraries be recompiled. See the
description of the GNAT LIBRARY command in the OpenVMS version
of the GNAT Users Guide for details on the use of this command.
Pragma Ident
Syntax:
pragma Ident (static_string_EXPRESSION);
This pragma provides a string identification in the generated object file,
if the system supports the concept of this kind of identification string.
This pragma is allowed only in the outermost declarative part or
declarative items of a compilation unit. If more than one Ident
pragma is given, only the last one processed is effective.
On OpenVMS systems, the effect of the pragma is identical to the effect of
the DEC Ada 83 pragma of the same name. Note that in DEC Ada 83, the
maximum allowed length is 31 characters, so if it is important to
maintain compatibility with this compiler, you should obey this length
limit.
Pragma Import_Exception
Syntax:
pragma Import_Exception (
[Internal =>] LOCAL_NAME,
[, [External =>] EXTERNAL_SYMBOL,]
[, [Form =>] Ada | VMS]
[, [Code =>] static_integer_EXPRESSION]);
EXTERNAL_SYMBOL ::=
IDENTIFIER
| static_string_EXPRESSION
This pragma is implemented only in the OpenVMS implementation of GNAT.
It allows OpenVMS conditions (for example, from OpenVMS system services or
other OpenVMS languages) to be propagated to Ada programs as Ada exceptions.
The pragma specifies that the exception associated with an exception
declaration in an Ada program be defined externally (in non-Ada code).
For further details on this pragma, see the
DEC Ada Language Reference Manual, section 13.9a.3.1.
Pragma Import_Function
Syntax:
pragma Import_Function (
[Internal =>] LOCAL_NAME,
[, [External =>] EXTERNAL_SYMBOL]
[, [Parameter_Types =>] PARAMETER_TYPES]
[, [Result_Type =>] SUBTYPE_MARK]
[, [Mechanism =>] MECHANISM]
[, [Result_Mechanism =>] MECHANISM_NAME]
[, [First_Optional_Parameter =>] IDENTIFIER]);
EXTERNAL_SYMBOL ::=
IDENTIFIER
| static_string_EXPRESSION
PARAMETER_TYPES ::=
null
| TYPE_DESIGNATOR {, TYPE_DESIGNATOR}
TYPE_DESIGNATOR ::=
subtype_NAME
| subtype_Name ' Access
MECHANISM ::=
MECHANISM_NAME
| (MECHANISM_ASSOCIATION {, MECHANISM_ASSOCIATION})
MECHANISM_ASSOCIATION ::=
[formal_parameter_NAME =>] MECHANISM_NAME
MECHANISM_NAME ::=
Value
| Reference
| Descriptor [([Class =>] CLASS_NAME)]
CLASS_NAME ::= ubs | ubsb | uba | s | sb | a | nca
This pragma is used in conjunction with a pragma Import to
specify additional information for an imported function. The pragma
Import (or equivalent pragma Interface) must precede the
Import_Function pragma and both must appear in the same
declarative part as the function specification.
The Internal argument must uniquely designate
the function to which the
pragma applies. If more than one function name exists of this name in
the declarative part you must use the Parameter_Types and
Result_Type parameters to achieve the required unique
designation. Subtype marks in these parameters must exactly match the
subtypes in the corresponding function specification, using positional
notation to match parameters with subtype marks.
The form with an 'Access attribute can be used to match an
anonymous access parameter.
You may optionally use the Mechanism and Result_Mechanism
parameters to specify passing mechanisms for the
parameters and result. If you specify a single mechanism name, it
applies to all parameters. Otherwise you may specify a mechanism on a
parameter by parameter basis using either positional or named
notation. If the mechanism is not specified, the default mechanism
is used.
Passing by descriptor is supported only on the OpenVMS ports of GNAT.
First_Optional_Parameter applies only to OpenVMS ports of GNAT.
It specifies that the designated parameter and all following parameters
are optional, meaning that they are not passed at the generated code
level (this is distinct from the notion of optional parameters in Ada
where the parameters are passed anyway with the designated optional
parameters). All optional parameters must be of mode IN and have
default parameter values that are either known at compile time
expressions, or uses of the 'Null_Parameter attribute.
Pragma Import_Object
Syntax:
pragma Import_Object
[Internal =>] LOCAL_NAME,
[, [External =>] EXTERNAL_SYMBOL],
[, [Size =>] EXTERNAL_SYMBOL]);
EXTERNAL_SYMBOL ::=
IDENTIFIER
| static_string_EXPRESSION
This pragma designates an object as imported, and apart from the
extended rules for external symbols, is identical in effect to the use of
the normal Import pragma applied to an object. Unlike the
subprogram case, you need not use a separate Import pragma,
although you may do so (and probably should do so from a portability
point of view). size is syntax checked, but otherwise ignored by
GNAT.
Pragma Import_Procedure
Syntax:
pragma Import_Procedure (
[Internal =>] LOCAL_NAME,
[, [External =>] EXTERNAL_SYMBOL]
[, [Parameter_Types =>] PARAMETER_TYPES]
[, [Mechanism =>] MECHANISM]
[, [First_Optional_Parameter =>] IDENTIFIER]);
EXTERNAL_SYMBOL ::=
IDENTIFIER
| static_string_EXPRESSION
PARAMETER_TYPES ::=
null
| TYPE_DESIGNATOR {, TYPE_DESIGNATOR}
TYPE_DESIGNATOR ::=
subtype_NAME
| subtype_Name ' Access
MECHANISM ::=
MECHANISM_NAME
| (MECHANISM_ASSOCIATION {, MECHANISM_ASSOCIATION})
MECHANISM_ASSOCIATION ::=
[formal_parameter_NAME =>] MECHANISM_NAME
MECHANISM_NAME ::=
Value
| Reference
| Descriptor [([Class =>] CLASS_NAME)]
CLASS_NAME ::= ubs | ubsb | uba | s | sb | a | nca
This pragma is identical to Import_Function except that it
applies to a procedure rather than a function and the parameters
Result_Type and Result_Mechanism are not permitted.
Pragma Import_Valued_Procedure
Syntax:
pragma Import_Valued_Procedure (
[Internal =>] LOCAL_NAME,
[, [External =>] EXTERNAL_SYMBOL]
[, [Parameter_Types =>] PARAMETER_TYPES]
[, [Mechanism =>] MECHANISM]
[, [First_Optional_Parameter =>] IDENTIFIER]);
EXTERNAL_SYMBOL ::=
IDENTIFIER
| static_string_EXPRESSION
PARAMETER_TYPES ::=
null
| TYPE_DESIGNATOR {, TYPE_DESIGNATOR}
TYPE_DESIGNATOR ::=
subtype_NAME
| subtype_Name ' Access
MECHANISM ::=
MECHANISM_NAME
| (MECHANISM_ASSOCIATION {, MECHANISM_ASSOCIATION})
MECHANISM_ASSOCIATION ::=
[formal_parameter_NAME =>] MECHANISM_NAME
MECHANISM_NAME ::=
Value
| Reference
| Descriptor [([Class =>] CLASS_NAME)]
CLASS_NAME ::= ubs | ubsb | uba | s | sb | a | nca
This pragma is identical to Import_Procedure except that the
first parameter of local_name, which must be present, must be of
mode OUT, and externally the subprogram is treated as a function
with this parameter as the result of the function. The purpose of this
capability is to allow the use of OUT and IN OUT
parameters in interfacing to external functions (which are not permitted
in Ada functions). You may optionally use the Mechanism
parameters to specify passing mechanisms for the parameters.
If you specify a single mechanism name, it applies to all parameters.
Otherwise you may specify a mechanism on a parameter by parameter
basis using either positional or named notation. If the mechanism is not
specified, the default mechanism is used.
Note that it is important to use this pragma in conjunction with a separate
pragma Import that specifies the desired convention, since otherwise the
default convention is Ada, which is almost certainly not what is required.
Pragma Initialize_Scalars
Syntax:
pragma Initialize_Scalars;
This pragma is similar to Normalize_Scalars conceptually but has
two important differences. First, there is no requirement for the pragma
to be used uniformly in all units of a partition, in particular, it is fine
to use this just for some or all of the application units of a partition,
without needing to recompile the run-time library.
In the case where some units are compiled with the pragma, and some without,
then a declaration of a variable where the type is defined in package
Standard or is locally declared will always be subject to initialization,
as will any declaration of a scalar variable. For composite variables,
whether the variable is initialized may also depend on whether the package
in which the type of the variable is declared is compiled with the pragma.
The other important difference is that there is control over the value used
for initializing scalar objects. At bind time, you can select whether to
initialize with invalid values (like Normalize_Scalars), or with high or
low values, or with a specified bit pattern. See the users guide for binder
options for specifying these cases.
This means that you can compile a program, and then without having to
recompile the program, you can run it with different values being used
for initializing otherwise uninitialized values, to test if your program
behavior depends on the choice. Of course the behavior should not change,
and if it does, then most likely you have an erroneous reference to an
uninitialized value.
Note that pragma Initialize_Scalars is particularly useful in
conjunction with the enhanced validity checking that is now provided
in GNAT, which checks for invalid values under more conditions.
Using this feature (see description of the -gnatV flag in the
users guide) in conjunction with pragma Initialize_Scalars
provides a powerful new tool to assist in the detection of problems
caused by uninitialized variables.
Pragma Inline_Always
Syntax:
pragma Inline_Always (NAME [, NAME]);
Similar to pragma Inline except that inlining is not subject to
the use of option -gnatn and the inlining happens regardless of
whether this option is used.
Pragma Inline_Generic
Syntax:
pragma Inline_Generic (generic_package_NAME);
This is implemented for compatibility with DEC Ada 83 and is recognized,
but otherwise ignored, by GNAT. All generic instantiations are inlined
by default when using GNAT.
Pragma Interface
Syntax:
pragma Interface (
[Convention =>] convention_identifier,
[Entity =>] local_name
[, [External_Name =>] static_string_expression],
[, [Link_Name =>] static_string_expression]);
This pragma is identical in syntax and semantics to
the standard Ada 95 pragma Import. It is provided for compatibility
with Ada 83. The definition is upwards compatible both with pragma
Interface as defined in the Ada 83 Reference Manual, and also
with some extended implementations of this pragma in certain Ada 83
implementations.
Pragma Interface_Name
Syntax:
pragma Interface_Name (
[Entity =>] LOCAL_NAME
[, [External_Name =>] static_string_EXPRESSION]
[, [Link_Name =>] static_string_EXPRESSION]);
This pragma provides an alternative way of specifying the interface name
for an interfaced subprogram, and is provided for compatibility with Ada
83 compilers that use the pragma for this purpose. You must provide at
least one of External_Name or Link_Name.
Pragma Interrupt_Handler
Syntax:
pragma Interrupt_Handler (procedure_LOCAL_NAME);
This program unit pragma is supported for parameterless protected procedures
as described in Annex C of the Ada Reference Manual. On the AAMP target
the pragma can also be specified for nonprotected parameterless procedures
that are declared at the library level (which includes procedures
declared at the top level of a library package). In the case of AAMP,
when this pragma is applied to a nonprotected procedure, the instruction
IERET is generated for returns from the procedure, enabling
maskable interrupts, in place of the normal return instruction.
Pragma Interrupt_State
Syntax:
pragma Interrupt_State (Name => value, State => SYSTEM | RUNTIME | USER);
Normally certain interrupts are reserved to the implementation. Any attempt
to attach an interrupt causes Program_Error to be raised, as described in
RM C.3.2(22). A typical example is the SIGINT interrupt used in
many systems for an Ctrl-C interrupt. Normally this interrupt is
reserved to the implementation, so that Ctrl-C can be used to
interrupt execution. Additionally, signals such as SIGSEGV,
SIGABRT, SIGFPE and SIGILL are often mapped to specific
Ada exceptions, or used to implement run-time functions such as the
abort statement and stack overflow checking.
Pragma Interrupt_State provides a general mechanism for overriding
such uses of interrupts. It subsumes the functionality of pragma
Unreserve_All_Interrupts. Pragma Interrupt_State is not
available on OS/2, Windows or VMS. On all other platforms than VxWorks,
it applies to signals; on VxWorks, it applies to vectored hardware interrupts
and may be used to mark interrupts required by the board support package
as reserved.
Interrupts can be in one of three states:
- System
The interrupt is reserved (no Ada handler can be installed), and the
Ada run-time may not install a handler. As a result you are guaranteed
standard system default action if this interrupt is raised.
- Runtime
The interrupt is reserved (no Ada handler can be installed). The run time
is allowed to install a handler for internal control purposes, but is
not required to do so.
- User
The interrupt is unreserved. The user may install a handler to provide
some other action.
These states are the allowed values of the State parameter of the
pragma. The Name parameter is a value of the type
Ada.Interrupts.Interrupt_ID. Typically, it is a name declared in
Ada.Interrupts.Names.
This is a configuration pragma, and the binder will check that there
are no inconsistencies between different units in a partition in how a
given interrupt is specified. It may appear anywhere a pragma is legal.
The effect is to move the interrupt to the specified state.
By declaring interrupts to be SYSTEM, you guarantee the standard system
action, such as a core dump.
By declaring interrupts to be USER, you guarantee that you can install
a handler.
Note that certain signals on many operating systems cannot be caught and
handled by applications. In such cases, the pragma is ignored. See the
operating system documentation, or the value of the array Reserved
declared in the specification of package System.OS_Interface.
Overriding the default state of signals used by the Ada runtime may interfere
with an application's runtime behavior in the cases of the synchronous signals,
and in the case of the signal used to implement the abort statement.
Pragma Keep_Names
Syntax:
pragma Keep_Names ([On =>] enumeration_first_subtype_LOCAL_NAME);
The LOCAL_NAME argument
must refer to an enumeration first subtype
in the current declarative part. The effect is to retain the enumeration
literal names for use by Image and Value even if a global
Discard_Names pragma applies. This is useful when you want to
generally suppress enumeration literal names and for example you therefore
use a Discard_Names pragma in the gnat.adc file, but you
want to retain the names for specific enumeration types.
Pragma License
Syntax:
pragma License (Unrestricted | GPL | Modified_GPL | Restricted);
This pragma is provided to allow automated checking for appropriate license
conditions with respect to the standard and modified GPL. A pragma
License, which is a configuration pragma that typically appears at
the start of a source file or in a separate gnat.adc file, specifies
the licensing conditions of a unit as follows:
- Unrestricted
This is used for a unit that can be freely used with no license restrictions.
Examples of such units are public domain units, and units from the Ada
Reference Manual.
- GPL
This is used for a unit that is licensed under the unmodified GPL, and which
therefore cannot be
with'ed by a restricted unit.
- Modified_GPL
This is used for a unit licensed under the GNAT modified GPL that includes
a special exception paragraph that specifically permits the inclusion of
the unit in programs without requiring the entire program to be released
under the GPL. This is the license used for the GNAT run-time which ensures
that the run-time can be used freely in any program without GPL concerns.
- Restricted
This is used for a unit that is restricted in that it is not permitted to
depend on units that are licensed under the GPL. Typical examples are
proprietary code that is to be released under more restrictive license
conditions. Note that restricted units are permitted to
with units
which are licensed under the modified GPL (this is the whole point of the
modified GPL).
Normally a unit with no License pragma is considered to have an
unknown license, and no checking is done. However, standard GNAT headers
are recognized, and license information is derived from them as follows.
A GNAT license header starts with a line containing 78 hyphens. The following
comment text is searched for the appearance of any of the following strings.
If the string “GNU General Public License” is found, then the unit is assumed
to have GPL license, unless the string “As a special exception” follows, in
which case the license is assumed to be modified GPL.
If one of the strings
“This specification is adapted from the Ada Semantic Interface” or
“This specification is derived from the Ada Reference Manual” is found
then the unit is assumed to be unrestricted.
These default actions means that a program with a restricted license pragma
will automatically get warnings if a GPL unit is inappropriately
with'ed. For example, the program:
with Sem_Ch3;
with GNAT.Sockets;
procedure Secret_Stuff is
...
end Secret_Stuff
if compiled with pragma License (Restricted) in a
gnat.adc file will generate the warning:
1. with Sem_Ch3;
|
>>> license of withed unit "Sem_Ch3" is incompatible
2. with GNAT.Sockets;
3. procedure Secret_Stuff is
Here we get a warning on Sem_Ch3 since it is part of the GNAT
compiler and is licensed under the
GPL, but no warning for GNAT.Sockets which is part of the GNAT
run time, and is therefore licensed under the modified GPL.
Pragma Link_With
Syntax:
pragma Link_With (static_string_EXPRESSION {,static_string_EXPRESSION});
This pragma is provided for compatibility with certain Ada 83 compilers.
It has exactly the same effect as pragma Linker_Options except
that spaces occurring within one of the string expressions are treated
as separators. For example, in the following case:
pragma Link_With ("-labc -ldef");
results in passing the strings -labc and -ldef as two
separate arguments to the linker. In addition pragma Link_With allows
multiple arguments, with the same effect as successive pragmas.
Pragma Linker_Alias
Syntax:
pragma Linker_Alias (
[Entity =>] LOCAL_NAME
[Alias =>] static_string_EXPRESSION);
This pragma establishes a linker alias for the given named entity. For
further details on the exact effect, consult the GCC manual.
Pragma Linker_Section
Syntax:
pragma Linker_Section (
[Entity =>] LOCAL_NAME
[Section =>] static_string_EXPRESSION);
This pragma specifies the name of the linker section for the given entity.
For further details on the exact effect, consult the GCC manual.
Pragma Long_Float
Syntax:
pragma Long_Float (FLOAT_FORMAT);
FLOAT_FORMAT ::= D_Float | G_Float
This pragma is implemented only in the OpenVMS implementation of GNAT.
It allows control over the internal representation chosen for the predefined
type Long_Float and for floating point type representations with
digits specified in the range 7 through 15.
For further details on this pragma, see the
DEC Ada Language Reference Manual, section 3.5.7b. Note that to use
this pragma, the standard runtime libraries must be recompiled. See the
description of the GNAT LIBRARY command in the OpenVMS version
of the GNAT User's Guide for details on the use of this command.
Pragma Machine_Attribute
Syntax:
pragma Machine_Attribute (
[Attribute_Name =>] string_EXPRESSION,
[Entity =>] LOCAL_NAME);
Machine dependent attributes can be specified for types and/or
declarations. Currently only subprogram entities are supported. This
pragma is semantically equivalent to
__attribute__((string_expression)) in GNU C,
where string_expression is
recognized by the GNU C macros VALID_MACHINE_TYPE_ATTRIBUTE and
VALID_MACHINE_DECL_ATTRIBUTE which are defined in the
configuration header file tm.h for each machine. See the GCC
manual for further information.
Pragma Main_Storage
Syntax:
pragma Main_Storage
(MAIN_STORAGE_OPTION [, MAIN_STORAGE_OPTION]);
MAIN_STORAGE_OPTION ::=
[WORKING_STORAGE =>] static_SIMPLE_EXPRESSION
| [TOP_GUARD =>] static_SIMPLE_EXPRESSION
This pragma is provided for compatibility with OpenVMS VAX Systems. It has
no effect in GNAT, other than being syntax checked. Note that the pragma
also has no effect in DEC Ada 83 for OpenVMS Alpha Systems.
Pragma No_Return
Syntax:
pragma No_Return (procedure_LOCAL_NAME);
procedure_local_NAME must refer to one or more procedure
declarations in the current declarative part. A procedure to which this
pragma is applied may not contain any explicit return statements,
and also may not contain any implicit return statements from falling off
the end of a statement sequence. One use of this pragma is to identify
procedures whose only purpose is to raise an exception.
Another use of this pragma is to suppress incorrect warnings about
missing returns in functions, where the last statement of a function
statement sequence is a call to such a procedure.
Pragma Normalize_Scalars
Syntax:
pragma Normalize_Scalars;
This is a language defined pragma which is fully implemented in GNAT. The
effect is to cause all scalar objects that are not otherwise initialized
to be initialized. The initial values are implementation dependent and
are as follows:
Standard.Character- Objects whose root type is Standard.Character are initialized to
Character'Last. This will be out of range of the subtype only if
the subtype range excludes this value.
Standard.Wide_Character- Objects whose root type is Standard.Wide_Character are initialized to
Wide_Character'Last. This will be out of range of the subtype only if
the subtype range excludes this value.
Integer types- Objects of an integer type are initialized to base_type'First, where
base_type is the base type of the object type. This will be out of range
of the subtype only if the subtype range excludes this value. For example,
if you declare the subtype:
subtype Ityp is integer range 1 .. 10;
then objects of type x will be initialized to Integer'First, a negative
number that is certainly outside the range of subtype Ityp.
Real types- Objects of all real types (fixed and floating) are initialized to
base_type'First, where base_Type is the base type of the object type.
This will be out of range of the subtype only if the subtype range
excludes this value.
Modular types- Objects of a modular type are initialized to typ'Last. This will be out
of range of the subtype only if the subtype excludes this value.
Enumeration types- Objects of an enumeration type are initialized to all one-bits, i.e. to
the value
2 ** typ'Size - 1. This will be out of range of the
enumeration subtype in all cases except where the subtype contains
exactly 2**8, 2**16, or 2**32 elements.
Pragma Obsolescent
Syntax:
pragma Obsolescent [(static_string_EXPRESSION)];
This pragma must occur immediately following a subprogram
declaration. It indicates that the associated function or procedure
is considered obsolescent and should not be used. Typically this is
used when an API must be modified by eventually removing or modifying
existing subprograms. The pragma can be used at an intermediate stage
when the subprogram is still present, but will be removed later.
The effect of this pragma is to output a warning message that the
subprogram is obsolescent if the appropriate warning option in the
compiler is activated. If a parameter is present, then a second
warning message is given containing this text.
Pragma Passive
Syntax:
pragma Passive ([Semaphore | No]);
Syntax checked, but otherwise ignored by GNAT. This is recognized for
compatibility with DEC Ada 83 implementations, where it is used within a
task definition to request that a task be made passive. If the argument
Semaphore is present, or the argument is omitted, then DEC Ada 83
treats the pragma as an assertion that the containing task is passive
and that optimization of context switch with this task is permitted and
desired. If the argument No is present, the task must not be
optimized. GNAT does not attempt to optimize any tasks in this manner
(since protected objects are available in place of passive tasks).
Pragma Polling
Syntax:
pragma Polling (ON | OFF);
This pragma controls the generation of polling code. This is normally off.
If pragma Polling (ON) is used then periodic calls are generated to
the routine Ada.Exceptions.Poll. This routine is a separate unit in the
runtime library, and can be found in file a-excpol.adb.
Pragma Polling can appear as a configuration pragma (for example it
can be placed in the gnat.adc file) to enable polling globally, or it
can be used in the statement or declaration sequence to control polling
more locally.
A call to the polling routine is generated at the start of every loop and
at the start of every subprogram call. This guarantees that the Poll
routine is called frequently, and places an upper bound (determined by
the complexity of the code) on the period between two Poll calls.
The primary purpose of the polling interface is to enable asynchronous
aborts on targets that cannot otherwise support it (for example Windows
NT), but it may be used for any other purpose requiring periodic polling.
The standard version is null, and can be replaced by a user program. This
will require re-compilation of the Ada.Exceptions package that can
be found in files a-except.ads and a-except.adb.
A standard alternative unit (in file 4wexcpol.adb in the standard GNAT
distribution) is used to enable the asynchronous abort capability on
targets that do not normally support the capability. The version of
Poll in this file makes a call to the appropriate runtime routine
to test for an abort condition.
Note that polling can also be enabled by use of the -gnatP switch. See
the GNAT User's Guide for details.
Pragma Propagate_Exceptions
Syntax:
pragma Propagate_Exceptions (subprogram_LOCAL_NAME);
This pragma indicates that the given entity, which is the name of an
imported foreign-language subprogram may receive an Ada exception,
and that the exception should be propagated. It is relevant only if
zero cost exception handling is in use, and is thus never needed if
the alternative longjmp / setjmp implementation of
exceptions is used (although it is harmless to use it in such cases).
The implementation of fast exceptions always properly propagates
exceptions through Ada code, as described in the Ada Reference Manual.
However, this manual is silent about the propagation of exceptions
through foreign code. For example, consider the
situation where P1 calls
P2, and P2 calls P3, where
P1 and P3 are in Ada, but P2 is in C.
P3 raises an Ada exception. The question is whether or not
it will be propagated through P2 and can be handled in
P1.
For the longjmp / setjmp implementation of exceptions,
the answer is always yes. For some targets on which zero cost exception
handling is implemented, the answer is also always yes. However, there
are some targets, notably in the current version all x86 architecture
targets, in which the answer is that such propagation does not
happen automatically. If such propagation is required on these
targets, it is mandatory to use Propagate_Exceptions to
name all foreign language routines through which Ada exceptions
may be propagated.
Pragma Psect_Object
Syntax:
pragma Psect_Object (
[Internal =>] LOCAL_NAME,
[, [External =>] EXTERNAL_SYMBOL]
[, [Size =>] EXTERNAL_SYMBOL]);
EXTERNAL_SYMBOL ::=
IDENTIFIER
| static_string_EXPRESSION
This pragma is identical in effect to pragma Common_Object.
Pragma Pure_Function
Syntax:
pragma Pure_Function ([Entity =>] function_LOCAL_NAME);
This pragma appears in the same declarative part as a function
declaration (or a set of function declarations if more than one
overloaded declaration exists, in which case the pragma applies
to all entities). It specifies that the function Entity is
to be considered pure for the purposes of code generation. This means
that the compiler can assume that there are no side effects, and
in particular that two calls with identical arguments produce the
same result. It also means that the function can be used in an
address clause.
Note that, quite deliberately, there are no static checks to try
to ensure that this promise is met, so Pure_Function can be used
with functions that are conceptually pure, even if they do modify
global variables. For example, a square root function that is
instrumented to count the number of times it is called is still
conceptually pure, and can still be optimized, even though it
modifies a global variable (the count). Memo functions are another
example (where a table of previous calls is kept and consulted to
avoid re-computation).
Note: Most functions in a Pure package are automatically pure, and
there is no need to use pragma Pure_Function for such functions. One
exception is any function that has at least one formal of type
System.Address or a type derived from it. Such functions are not
considered pure by default, since the compiler assumes that the
Address parameter may be functioning as a pointer and that the
referenced data may change even if the address value does not.
Similarly, imported functions are not consdered to be pure by default,
since there is no way of checking that they are in fact pure. The use
of pragma Pure_Function for such a function will override these default
assumption, and cause the compiler to treat a designated subprogram as pure
in these cases.
Note: If pragma Pure_Function is applied to a renamed function, it
applies to the underlying renamed function. This can be used to
disambiguate cases of overloading where some but not all functions
in a set of overloaded functions are to be designated as pure.
Pragma Ravenscar
Syntax:
pragma Ravenscar;
A configuration pragma that establishes the following set of restrictions:
No_Abort_Statements- [RM D.7] There are no abort_statements, and there are
no calls to Task_Identification.Abort_Task.
No_Select_Statements- There are no select_statements.
No_Task_Hierarchy- [RM D.7] All (non-environment) tasks depend
directly on the environment task of the partition.
No_Task_Allocators- [RM D.7] There are no allocators for task types
or types containing task subcomponents.
No_Dynamic_Priorities- [RM D.7] There are no semantic dependencies on the package Dynamic_Priorities.
No_Terminate_Alternatives- [RM D.7] There are no selective_accepts with terminate_alternatives
No_Dynamic_Interrupts- There are no semantic dependencies on Ada.Interrupts.
No_Implicit_Heap_Allocations- [RM D.7] No constructs are allowed to cause implicit heap allocation
No_Protected_Type_Allocators- There are no allocators for protected types or
types containing protected subcomponents.
No_Local_Protected_Objects- Protected objects and access types that designate
such objects shall be declared only at library level.
No_Requeue- Requeue statements are not allowed.
No_Calendar- There are no semantic dependencies on the package Ada.Calendar.
No_Relative_Delay- There are no delay_relative_statements.
No_Task_Attributes- There are no semantic dependencies on the Ada.Task_Attributes package and
there are no references to the attributes Callable and Terminated [RM 9.9].
Boolean_Entry_Barriers- Entry barrier condition expressions shall be boolean
objects which are declared in the protected type
which contains the entry.
Max_Asynchronous_Select_Nesting = 0- [RM D.7] Specifies the maximum dynamic nesting level of asynchronous_selects.
A value of zero prevents the use of any asynchronous_select.
Max_Task_Entries = 0- [RM D.7] Specifies the maximum number of entries
per task. The bounds of every entry family
of a task unit shall be static, or shall be
defined by a discriminant of a subtype whose
corresponding bound is static. A value of zero
indicates that no rendezvous are possible. For
the Ravenscar pragma, the value of Max_Task_Entries is always
0 (zero).
Max_Protected_Entries = 1- [RM D.7] Specifies the maximum number of entries per
protected type. The bounds of every entry family of
a protected unit shall be static, or shall be defined
by a discriminant of a subtype whose corresponding
bound is static. For the Ravenscar pragma the value of
Max_Protected_Entries is always 1.
Max_Select_Alternatives = 0- [RM D.7] Specifies the maximum number of alternatives in a selective_accept.
For the Ravenscar pragma the value is always 0.
No_Task_Termination- Tasks which terminate are erroneous.
No_Entry_Queue- No task can be queued on a protected entry. Note that this restrictions is
checked at run time. The violation of this restriction generates a
Program_Error exception.
This set of restrictions corresponds to the definition of the “Ravenscar
Profile” for limited tasking, devised and published by the
International Real-Time Ada Workshop, 1997,
and whose most recent description is available at
ftp://ftp.openravenscar.org/openravenscar/ravenscar00.pdf.
The above set is a superset of the restrictions provided by pragma
Restricted_Run_Time, it includes five additional restrictions
(Boolean_Entry_Barriers, No_Select_Statements,
No_Calendar,
No_Relative_Delay and No_Task_Termination). This means
that pragma Ravenscar, like the pragma Restricted_Run_Time,
automatically causes the use of a simplified, more efficient version
of the tasking run-time system.
Pragma Restricted_Run_Time
Syntax:
pragma Restricted_Run_Time;
A configuration pragma that establishes the following set of restrictions:
- No_Abort_Statements
- No_Entry_Queue
- No_Task_Hierarchy
- No_Task_Allocators
- No_Dynamic_Priorities
- No_Terminate_Alternatives
- No_Dynamic_Interrupts
- No_Protected_Type_Allocators
- No_Local_Protected_Objects
- No_Requeue
- No_Task_Attributes
- Max_Asynchronous_Select_Nesting = 0
- Max_Task_Entries = 0
- Max_Protected_Entries = 1
- Max_Select_Alternatives = 0
This set of restrictions causes the automatic selection of a simplified
version of the run time that provides improved performance for the
limited set of tasking functionality permitted by this set of restrictions.
Pragma Restriction_Warnings
Syntax:
pragma Restriction_Warnings
(restriction_IDENTIFIER {, restriction_IDENTIFIER});
This pragma allows a series of restriction identifiers to be
specified (the list of allowed identifiers is the same as for
pragma Restrictions). For each of these identifiers
the compiler checks for violations of the restriction, but
generates a warning message rather than an error message
if the restriction is violated.
Pragma Source_File_Name
Syntax:
pragma Source_File_Name (
[Unit_Name =>] unit_NAME,
Spec_File_Name => STRING_LITERAL);
pragma Source_File_Name (
[Unit_Name =>] unit_NAME,
Body_File_Name => STRING_LITERAL);
Use this to override the normal naming convention. It is a configuration
pragma, and so has the usual applicability of configuration pragmas
(i.e. it applies to either an entire partition, or to all units in a
compilation, or to a single unit, depending on how it is used.
unit_name is mapped to file_name_literal. The identifier for
the second argument is required, and indicates whether this is the file
name for the spec or for the body.
Another form of the Source_File_Name pragma allows
the specification of patterns defining alternative file naming schemes
to apply to all files.
pragma Source_File_Name
(Spec_File_Name => STRING_LITERAL
[,Casing => CASING_SPEC]
[,Dot_Replacement => STRING_LITERAL]);
pragma Source_File_Name
(Body_File_Name => STRING_LITERAL
[,Casing => CASING_SPEC]
[,Dot_Replacement => STRING_LITERAL]);
pragma Source_File_Name
(Subunit_File_Name => STRING_LITERAL
[,Casing => CASING_SPEC]
[,Dot_Replacement => STRING_LITERAL]);
CASING_SPEC ::= Lowercase | Uppercase | Mixedcase
The first argument is a pattern that contains a single asterisk indicating
the point at which the unit name is to be inserted in the pattern string
to form the file name. The second argument is optional. If present it
specifies the casing of the unit name in the resulting file name string.
The default is lower case. Finally the third argument allows for systematic
replacement of any dots in the unit name by the specified string literal.
A pragma Source_File_Name cannot appear after a
Pragma Source_File_Name_Project.
For more details on the use of the Source_File_Name pragma,
see the sections “Using Other File Names” and
“Alternative File Naming Schemes” in the GNAT User's Guide.
Pragma Source_File_Name_Project
This pragma has the same syntax and semantics as pragma Source_File_Name.
It is only allowed as a stand alone configuration pragma.
It cannot appear after a Pragma Source_File_Name, and
most importantly, once pragma Source_File_Name_Project appears,
no further Source_File_Name pragmas are allowed.
The intention is that Source_File_Name_Project pragmas are always
generated by the Project Manager in a manner consistent with the naming
specified in a project file, and when naming is controlled in this manner,
it is not permissible to attempt to modify this naming scheme using
Source_File_Name pragmas (which would not be known to the project manager).
Pragma Source_Reference
Syntax:
pragma Source_Reference (INTEGER_LITERAL, STRING_LITERAL);
This pragma must appear as the first line of a source file.
integer_literal is the logical line number of the line following
the pragma line (for use in error messages and debugging
information). string_literal is a static string constant that
specifies the file name to be used in error messages and debugging
information. This is most notably used for the output of gnatchop
with the -r switch, to make sure that the original unchopped
source file is the one referred to.
The second argument must be a string literal, it cannot be a static
string expression other than a string literal. This is because its value
is needed for error messages issued by all phases of the compiler.
Pragma Stream_Convert
Syntax:
pragma Stream_Convert (
[Entity =>] type_LOCAL_NAME,
[Read =>] function_NAME,
[Write =>] function NAME);
This pragma provides an efficient way of providing stream functions for
types defined in packages. Not only is it simpler to use than declaring
the necessary functions with attribute representation clauses, but more
significantly, it allows the declaration to made in such a way that the
stream packages are not loaded unless they are needed. The use of
the Stream_Convert pragma adds no overhead at all, unless the stream
attributes are actually used on the designated type.
The first argument specifies the type for which stream functions are
provided. The second parameter provides a function used to read values
of this type. It must name a function whose argument type may be any
subtype, and whose returned type must be the type given as the first
argument to the pragma.
The meaning of the Read
parameter is that if a stream attribute directly
or indirectly specifies reading of the type given as the first parameter,
then a value of the type given as the argument to the Read function is
read from the stream, and then the Read function is used to convert this
to the required target type.
Similarly the Write parameter specifies how to treat write attributes
that directly or indirectly apply to the type given as the first parameter.
It must have an input parameter of the type specified by the first parameter,
and the return type must be the same as the input type of the Read function.
The effect is to first call the Write function to convert to the given stream
type, and then write the result type to the stream.
The Read and Write functions must not be overloaded subprograms. If necessary
renamings can be supplied to meet this requirement.
The usage of this attribute is best illustrated by a simple example, taken
from the GNAT implementation of package Ada.Strings.Unbounded:
function To_Unbounded (S : String)
return Unbounded_String
renames To_Unbounded_String;
pragma Stream_Convert
(Unbounded_String, To_Unbounded, To_String);
The specifications of the referenced functions, as given in the Ada 95
Reference Manual are:
function To_Unbounded_String (Source : String)
return Unbounded_String;
function To_String (Source : Unbounded_String)
return String;
The effect is that if the value of an unbounded string is written to a
stream, then the representation of the item in the stream is in the same
format used for Standard.String, and this same representation is
expected when a value of this type is read from the stream.
Pragma Style_Checks
Syntax:
pragma Style_Checks (string_LITERAL | ALL_CHECKS |
On | Off [, LOCAL_NAME]);
This pragma is used in conjunction with compiler switches to control the
built in style checking provided by GNAT. The compiler switches, if set,
provide an initial setting for the switches, and this pragma may be used
to modify these settings, or the settings may be provided entirely by
the use of the pragma. This pragma can be used anywhere that a pragma
is legal, including use as a configuration pragma (including use in
the gnat.adc file).
The form with a string literal specifies which style options are to be
activated. These are additive, so they apply in addition to any previously
set style check options. The codes for the options are the same as those
used in the -gnaty switch to gcc or gnatmake.
For example the following two methods can be used to enable
layout checking:
The form ALL_CHECKS activates all standard checks (its use is equivalent
to the use of the gnaty switch with no options. See GNAT User's
Guide for details.
The forms with Off and On
can be used to temporarily disable style checks
as shown in the following example:
pragma Style_Checks ("k"); -- requires keywords in lower case
pragma Style_Checks (Off); -- turn off style checks
NULL; -- this will not generate an error message
pragma Style_Checks (On); -- turn style checks back on
NULL; -- this will generate an error message
Finally the two argument form is allowed only if the first argument is
On or Off. The effect is to turn of semantic style checks
for the specified entity, as shown in the following example:
pragma Style_Checks ("r"); -- require consistency of identifier casing
Arg : Integer;
Rf1 : Integer := ARG; -- incorrect, wrong case
pragma Style_Checks (Off, Arg);
Rf2 : Integer := ARG; -- OK, no error
Pragma Subtitle
Syntax:
pragma Subtitle ([Subtitle =>] STRING_LITERAL);
This pragma is recognized for compatibility with other Ada compilers
but is ignored by GNAT.
Pragma Suppress_All
Syntax:
pragma Suppress_All;
This pragma can only appear immediately following a compilation
unit. The effect is to apply Suppress (All_Checks) to the unit
which it follows. This pragma is implemented for compatibility with DEC
Ada 83 usage. The use of pragma Suppress (All_Checks) as a normal
configuration pragma is the preferred usage in GNAT.
Pragma Suppress_Exception_Locations
Syntax:
pragma Suppress_Exception_Locations;
In normal mode, a raise statement for an exception by default generates
an exception message giving the file name and line number for the location
of the raise. This is useful for debugging and logging purposes, but this
entails extra space for the strings for the messages. The configuration
pragma Suppress_Exception_Locations can be used to suppress the
generation of these strings, with the result that space is saved, but the
exception message for such raises is null. This configuration pragma may
appear in a global configuration pragma file, or in a specific unit as
usual. It is not required that this pragma be used consistently within
a partition, so it is fine to have some units within a partition compiled
with this pragma and others compiled in normal mode without it.
Pragma Suppress_Initialization
Syntax:
pragma Suppress_Initialization ([Entity =>] type_Name);
This pragma suppresses any implicit or explicit initialization
associated with the given type name for all variables of this type.
Pragma Task_Info
Syntax
pragma Task_Info (EXPRESSION);
This pragma appears within a task definition (like pragma
Priority) and applies to the task in which it appears. The
argument must be of type System.Task_Info.Task_Info_Type.
The Task_Info pragma provides system dependent control over
aspects of tasking implementation, for example, the ability to map
tasks to specific processors. For details on the facilities available
for the version of GNAT that you are using, see the documentation
in the specification of package System.Task_Info in the runtime
library.
Pragma Task_Name
Syntax
pragma Task_Name (string_EXPRESSION);
This pragma appears within a task definition (like pragma
Priority) and applies to the task in which it appears. The
argument must be of type String, and provides a name to be used for
the task instance when the task is created. Note that this expression
is not required to be static, and in particular, it can contain
references to task discriminants. This facility can be used to
provide different names for different tasks as they are created,
as illustrated in the example below.
The task name is recorded internally in the run-time structures
and is accessible to tools like the debugger. In addition the
routine Ada.Task_Identification.Image will return this
string, with a unique task address appended.
-- Example of the use of pragma Task_Name
with Ada.Task_Identification;
use Ada.Task_Identification;
with Text_IO; use Text_IO;
procedure t3 is
type Astring is access String;
task type Task_Typ (Name : access String) is
pragma Task_Name (Name.all);
end Task_Typ;
task body Task_Typ is
Nam : constant String := Image (Current_Task);
begin
Put_Line ("-->" & Nam (1 .. 14) & "<--");
end Task_Typ;
type Ptr_Task is access Task_Typ;
Task_Var : Ptr_Task;
begin
Task_Var :=
new Task_Typ (new String'("This is task 1"));
Task_Var :=
new Task_Typ (new String'("This is task 2"));
end;
Pragma Task_Storage
Syntax:
pragma Task_Storage (
[Task_Type =>] LOCAL_NAME,
[Top_Guard =>] static_integer_EXPRESSION);
This pragma specifies the length of the guard area for tasks. The guard
area is an additional storage area allocated to a task. A value of zero
means that either no guard area is created or a minimal guard area is
created, depending on the target. This pragma can appear anywhere a
Storage_Size attribute definition clause is allowed for a task
type.
Pragma Thread_Body
Syntax:
pragma Thread_Body (
[Entity =>] LOCAL_NAME,
[[Secondary_Stack_Size =>] static_integer_EXPRESSION)];
This pragma specifies that the subprogram whose name is given as the
Entity argument is a thread body, which will be activated
by being called via its Address from foreign code. The purpose is
to allow execution and registration of the foreign thread within the
Ada run-time system.
See the library unit System.Threads for details on the expansion of
a thread body subprogram, including the calls made to subprograms
within System.Threads to register the task. This unit also lists the
targets and runtime systems for which this pragma is supported.
A thread body subprogram may not be called directly from Ada code, and
it is not permitted to apply the Access (or Unrestricted_Access) attributes
to such a subprogram. The only legitimate way of calling such a subprogram
is to pass its Address to foreign code and then make the call from the
foreign code.
A thread body subprogram may have any parameters, and it may be a function
returning a result. The convention of the thread body subprogram may be
set in the usual manner using pragma Convention.
The secondary stack size parameter, if given, is used to set the size
of secondary stack for the thread. The secondary stack is allocated as
a local variable of the expanded thread body subprogram, and thus is
allocated out of the main thread stack size. If no secondary stack
size parameter is present, the default size (from the declaration in
System.Secondary_Stack is used.
Pragma Time_Slice
Syntax:
pragma Time_Slice (static_duration_EXPRESSION);
For implementations of GNAT on operating systems where it is possible
to supply a time slice value, this pragma may be used for this purpose.
It is ignored if it is used in a system that does not allow this control,
or if it appears in other than the main program unit.
Note that the effect of this pragma is identical to the effect of the
DEC Ada 83 pragma of the same name when operating under OpenVMS systems.
Pragma Title
Syntax:
pragma Title (TITLING_OPTION [, TITLING OPTION]);
TITLING_OPTION ::=
[Title =>] STRING_LITERAL,
| [Subtitle =>] STRING_LITERAL
Syntax checked but otherwise ignored by GNAT. This is a listing control
pragma used in DEC Ada 83 implementations to provide a title and/or
subtitle for the program listing. The program listing generated by GNAT
does not have titles or subtitles.
Unlike other pragmas, the full flexibility of named notation is allowed
for this pragma, i.e. the parameters may be given in any order if named
notation is used, and named and positional notation can be mixed
following the normal rules for procedure calls in Ada.
Pragma Unchecked_Union
Syntax:
pragma Unchecked_Union (first_subtype_LOCAL_NAME);
This pragma is used to declare that the specified type should be represented
in a manner
equivalent to a C union type, and is intended only for use in
interfacing with C code that uses union types. In Ada terms, the named
type must obey the following rules:
- It is a non-tagged non-limited record type.
- It has a single discrete discriminant with a default value.
- The component list consists of a single variant part.
- Each variant has a component list with a single component.
- No nested variants are allowed.
- No component has an explicit default value.
- No component has a non-static constraint.
In addition, given a type that meets the above requirements, the
following restrictions apply to its use throughout the program:
- The discriminant name can be mentioned only in an aggregate.
- No subtypes may be created of this type.
- The type may not be constrained by giving a discriminant value.
- The type cannot be passed as the actual for a generic formal with a
discriminant.
Equality and inequality operations on unchecked_unions are not
available, since there is no discriminant to compare and the compiler
does not even know how many bits to compare. It is implementation
dependent whether this is detected at compile time as an illegality or
whether it is undetected and considered to be an erroneous construct. In
GNAT, a direct comparison is illegal, but GNAT does not attempt to catch
the composite case (where two composites are compared that contain an
unchecked union component), so such comparisons are simply considered
erroneous.
The layout of the resulting type corresponds exactly to a C union, where
each branch of the union corresponds to a single variant in the Ada
record. The semantics of the Ada program is not changed in any way by
the pragma, i.e. provided the above restrictions are followed, and no
erroneous incorrect references to fields or erroneous comparisons occur,
the semantics is exactly as described by the Ada reference manual.
Pragma Suppress (Discriminant_Check) applies implicitly to the
type and the default convention is C.
Pragma Unimplemented_Unit
Syntax:
pragma Unimplemented_Unit;
If this pragma occurs in a unit that is processed by the compiler, GNAT
aborts with the message xxx not implemented, where
xxx is the name of the current compilation unit. This pragma is
intended to allow the compiler to handle unimplemented library units in
a clean manner.
The abort only happens if code is being generated. Thus you can use
specs of unimplemented packages in syntax or semantic checking mode.
Pragma Universal_Data
Syntax:
pragma Universal_Data [(library_unit_Name)];
This pragma is supported only for the AAMP target and is ignored for
other targets. The pragma specifies that all library-level objects
(Counter 0 data) associated with the library unit are to be accessed
and updated using universal addressing (24-bit addresses for AAMP5)
rather than the default of 16-bit Data Environment (DENV) addressing.
Use of this pragma will generally result in less efficient code for
references to global data associated with the library unit, but
allows such data to be located anywhere in memory. This pragma is
a library unit pragma, but can also be used as a configuration pragma
(including use in the gnat.adc file). The functionality
of this pragma is also available by applying the -univ switch on the
compilations of units where universal addressing of the data is desired.
Pragma Unreferenced
Syntax:
pragma Unreferenced (local_Name {, local_Name});
This pragma signals that the entities whose names are listed are
deliberately not referenced. This suppresses warnings about the
entities being unreferenced, and in addition a warning will be
generated if one of these entities is in fact referenced.
This is particularly useful for clearly signaling that a particular
parameter is not referenced in some particular subprogram implementation
and that this is deliberate. It can also be useful in the case of
objects declared only for their initialization or finalization side
effects.
If local_Name identifies more than one matching homonym in the
current scope, then the entity most recently declared is the one to which
the pragma applies.
The left hand side of an assignment does not count as a reference for the
purpose of this pragma. Thus it is fine to assign to an entity for which
pragma Unreferenced is given.
Pragma Unreserve_All_Interrupts
Syntax:
pragma Unreserve_All_Interrupts;
Normally certain interrupts are reserved to the implementation. Any attempt
to attach an interrupt causes Program_Error to be raised, as described in
RM C.3.2(22). A typical example is the SIGINT interrupt used in
many systems for a Ctrl-C interrupt. Normally this interrupt is
reserved to the implementation, so that Ctrl-C can be used to
interrupt execution.
If the pragma Unreserve_All_Interrupts appears anywhere in any unit in
a program, then all such interrupts are unreserved. This allows the
program to handle these interrupts, but disables their standard
functions. For example, if this pragma is used, then pressing
Ctrl-C will not automatically interrupt execution. However,
a program can then handle the SIGINT interrupt as it chooses.
For a full list of the interrupts handled in a specific implementation,
see the source code for the specification of Ada.Interrupts.Names in
file a-intnam.ads. This is a target dependent file that contains the
list of interrupts recognized for a given target. The documentation in
this file also specifies what interrupts are affected by the use of
the Unreserve_All_Interrupts pragma.
For a more general facility for controlling what interrupts can be
handled, see pragma Interrupt_State, which subsumes the functionality
of the Unreserve_All_Interrupts pragma.
Pragma Unsuppress
Syntax:
pragma Unsuppress (IDENTIFIER [, [On =>] NAME]);
This pragma undoes the effect of a previous pragma Suppress. If
there is no corresponding pragma Suppress in effect, it has no
effect. The range of the effect is the same as for pragma
Suppress. The meaning of the arguments is identical to that used
in pragma Suppress.
One important application is to ensure that checks are on in cases where
code depends on the checks for its correct functioning, so that the code
will compile correctly even if the compiler switches are set to suppress
checks.
Pragma Use_VADS_Size
Syntax:
pragma Use_VADS_Size;
This is a configuration pragma. In a unit to which it applies, any use
of the 'Size attribute is automatically interpreted as a use of the
'VADS_Size attribute. Note that this may result in incorrect semantic
processing of valid Ada 95 programs. This is intended to aid in the
handling of legacy code which depends on the interpretation of Size
as implemented in the VADS compiler. See description of the VADS_Size
attribute for further details.
Pragma Validity_Checks
Syntax:
pragma Validity_Checks (string_LITERAL | ALL_CHECKS | On | Off);
This pragma is used in conjunction with compiler switches to control the
built-in validity checking provided by GNAT. The compiler switches, if set
provide an initial setting for the switches, and this pragma may be used
to modify these settings, or the settings may be provided entirely by
the use of the pragma. This pragma can be used anywhere that a pragma
is legal, including use as a configuration pragma (including use in
the gnat.adc file).
The form with a string literal specifies which validity options are to be
activated. The validity checks are first set to include only the default
reference manual settings, and then a string of letters in the string
specifies the exact set of options required. The form of this string
is exactly as described for the -gnatVx compiler switch (see the
GNAT users guide for details). For example the following two methods
can be used to enable validity checking for mode in and
in out subprogram parameters:
The form ALL_CHECKS activates all standard checks (its use is equivalent
to the use of the gnatva switch.
The forms with Off and On
can be used to temporarily disable validity checks
as shown in the following example:
pragma Validity_Checks ("c"); -- validity checks for copies
pragma Validity_Checks (Off); -- turn off validity checks
A := B; -- B will not be validity checked
pragma Validity_Checks (On); -- turn validity checks back on
A := C; -- C will be validity checked
Pragma Volatile
Syntax:
pragma Volatile (local_NAME);
This pragma is defined by the Ada 95 Reference Manual, and the GNAT
implementation is fully conformant with this definition. The reason it
is mentioned in this section is that a pragma of the same name was supplied
in some Ada 83 compilers, including DEC Ada 83. The Ada 95 implementation
of pragma Volatile is upwards compatible with the implementation in
Dec Ada 83.
Pragma Warnings
Syntax:
pragma Warnings (On | Off [, LOCAL_NAME]);
Normally warnings are enabled, with the output being controlled by
the command line switch. Warnings (Off) turns off generation of
warnings until a Warnings (On) is encountered or the end of the
current unit. If generation of warnings is turned off using this
pragma, then no warning messages are output, regardless of the
setting of the command line switches.
The form with a single argument is a configuration pragma.
If the local_name parameter is present, warnings are suppressed for
the specified entity. This suppression is effective from the point where
it occurs till the end of the extended scope of the variable (similar to
the scope of Suppress).
Pragma Weak_External
Syntax:
pragma Weak_External ([Entity =>] LOCAL_NAME);
This pragma specifies that the given entity should be marked as a weak
external (one that does not have to be resolved) for the linker. For
further details, consult the GCC manual.
2 Implementation Defined Attributes
Ada 95 defines (throughout the Ada 95 reference manual,
summarized in annex K),
a set of attributes that provide useful additional functionality in all
areas of the language. These language defined attributes are implemented
in GNAT and work as described in the Ada 95 Reference Manual.
In addition, Ada 95 allows implementations to define additional
attributes whose meaning is defined by the implementation. GNAT provides
a number of these implementation-dependent attributes which can be used
to extend and enhance the functionality of the compiler. This section of
the GNAT reference manual describes these additional attributes.
Note that any program using these attributes may not be portable to
other compilers (although GNAT implements this set of attributes on all
platforms). Therefore if portability to other compilers is an important
consideration, you should minimize the use of these attributes.
Abort_Signal
Standard'Abort_Signal (Standard is the only allowed
prefix) provides the entity for the special exception used to signal
task abort or asynchronous transfer of control. Normally this attribute
should only be used in the tasking runtime (it is highly peculiar, and
completely outside the normal semantics of Ada, for a user program to
intercept the abort exception).
Address_Size
Standard'Address_Size (Standard is the only allowed
prefix) is a static constant giving the number of bits in an
Address. It is the same value as System.Address'Size,
but has the advantage of being static, while a direct
reference to System.Address'Size is non-static because Address
is a private type.
Asm_Input
The Asm_Input attribute denotes a function that takes two
parameters. The first is a string, the second is an expression of the
type designated by the prefix. The first (string) argument is required
to be a static expression, and is the constraint for the parameter,
(e.g. what kind of register is required). The second argument is the
value to be used as the input argument. The possible values for the
constant are the same as those used in the RTL, and are dependent on
the configuration file used to built the GCC back end.
Machine Code Insertions
Asm_Output
The Asm_Output attribute denotes a function that takes two
parameters. The first is a string, the second is the name of a variable
of the type designated by the attribute prefix. The first (string)
argument is required to be a static expression and designates the
constraint for the parameter (e.g. what kind of register is
required). The second argument is the variable to be updated with the
result. The possible values for constraint are the same as those used in
the RTL, and are dependent on the configuration file used to build the
GCC back end. If there are no output operands, then this argument may
either be omitted, or explicitly given as No_Output_Operands.
Machine Code Insertions
AST_Entry
This attribute is implemented only in OpenVMS versions of GNAT. Applied to
the name of an entry, it yields a value of the predefined type AST_Handler
(declared in the predefined package System, as extended by the use of
pragma Extend_System (Aux_DEC)). This value enables the given entry to
be called when an AST occurs. For further details, refer to the DEC Ada
Language Reference Manual, section 9.12a.
Bit
obj'Bit, where obj is any object, yields the bit
offset within the storage unit (byte) that contains the first bit of
storage allocated for the object. The value of this attribute is of the
type Universal_Integer, and is always a non-negative number not
exceeding the value of System.Storage_Unit.
For an object that is a variable or a constant allocated in a register,
the value is zero. (The use of this attribute does not force the
allocation of a variable to memory).
For an object that is a formal parameter, this attribute applies
to either the matching actual parameter or to a copy of the
matching actual parameter.
For an access object the value is zero. Note that
obj.all'Bit is subject to an Access_Check for the
designated object. Similarly for a record component
X.C'Bit is subject to a discriminant check and
X(I).Bit and X(I1..I2)'Bit
are subject to index checks.
This attribute is designed to be compatible with the DEC Ada 83 definition
and implementation of the Bit attribute.
Bit_Position
R.C'Bit, where R is a record object and C is one
of the fields of the record type, yields the bit
offset within the record contains the first bit of
storage allocated for the object. The value of this attribute is of the
type Universal_Integer. The value depends only on the field
C and is independent of the alignment of
the containing record R.
Code_Address
The 'Address
attribute may be applied to subprograms in Ada 95, but the
intended effect from the Ada 95 reference manual seems to be to provide
an address value which can be used to call the subprogram by means of
an address clause as in the following example:
procedure K is ...
procedure L;
for L'Address use K'Address;
pragma Import (Ada, L);
A call to L is then expected to result in a call to K.
In Ada 83, where there were no access-to-subprogram values, this was
a common work around for getting the effect of an indirect call.
GNAT implements the above use of Address and the technique
illustrated by the example code works correctly.
However, for some purposes, it is useful to have the address of the start
of the generated code for the subprogram. On some architectures, this is
not necessarily the same as the Address value described above.
For example, the Address value may reference a subprogram
descriptor rather than the subprogram itself.
The 'Code_Address attribute, which can only be applied to
subprogram entities, always returns the address of the start of the
generated code of the specified subprogram, which may or may not be
the same value as is returned by the corresponding 'Address
attribute.
Default_Bit_Order
Standard'Default_Bit_Order (Standard is the only
permissible prefix), provides the value System.Default_Bit_Order
as a Pos value (0 for High_Order_First, 1 for
Low_Order_First). This is used to construct the definition of
Default_Bit_Order in package System.
Elaborated
The prefix of the 'Elaborated attribute must be a unit name. The
value is a Boolean which indicates whether or not the given unit has been
elaborated. This attribute is primarily intended for internal use by the
generated code for dynamic elaboration checking, but it can also be used
in user programs. The value will always be True once elaboration of all
units has been completed.
Elab_Body
This attribute can only be applied to a program unit name. It returns
the entity for the corresponding elaboration procedure for elaborating
the body of the referenced unit. This is used in the main generated
elaboration procedure by the binder and is not normally used in any
other context. However, there may be specialized situations in which it
is useful to be able to call this elaboration procedure from Ada code,
e.g. if it is necessary to do selective re-elaboration to fix some
error.
Elab_Spec
This attribute can only be applied to a program unit name. It returns
the entity for the corresponding elaboration procedure for elaborating
the specification of the referenced unit. This is used in the main
generated elaboration procedure by the binder and is not normally used
in any other context. However, there may be specialized situations in
which it is useful to be able to call this elaboration procedure from
Ada code, e.g. if it is necessary to do selective re-elaboration to fix
some error.
Emax
The Emax attribute is provided for compatibility with Ada 83. See
the Ada 83 reference manual for an exact description of the semantics of
this attribute.
Enum_Rep
For every enumeration subtype S, S'Enum_Rep denotes a
function with the following spec:
function S'Enum_Rep (Arg : S'Base)
return Universal_Integer;
It is also allowable to apply Enum_Rep directly to an object of an
enumeration type or to a non-overloaded enumeration
literal. In this case S'Enum_Rep is equivalent to
typ'Enum_Rep(S) where typ is the type of the
enumeration literal or object.
The function returns the representation value for the given enumeration
value. This will be equal to value of the Pos attribute in the
absence of an enumeration representation clause. This is a static
attribute (i.e. the result is static if the argument is static).
S'Enum_Rep can also be used with integer types and objects,
in which case it simply returns the integer value. The reason for this
is to allow it to be used for (<>) discrete formal arguments in
a generic unit that can be instantiated with either enumeration types
or integer types. Note that if Enum_Rep is used on a modular
type whose upper bound exceeds the upper bound of the largest signed
integer type, and the argument is a variable, so that the universal
integer calculation is done at run-time, then the call to Enum_Rep
may raise Constraint_Error.
Epsilon
The Epsilon attribute is provided for compatibility with Ada 83. See
the Ada 83 reference manual for an exact description of the semantics of
this attribute.
Fixed_Value
For every fixed-point type S, S'Fixed_Value denotes a
function with the following specification:
function S'Fixed_Value (Arg : Universal_Integer)
return S;
The value returned is the fixed-point value V such that
V = Arg * S'Small
The effect is thus similar to first converting the argument to the
integer type used to represent S, and then doing an unchecked
conversion to the fixed-point type. The difference is
that there are full range checks, to ensure that the result is in range.
This attribute is primarily intended for use in implementation of the
input-output functions for fixed-point values.
Has_Discriminants
The prefix of the Has_Discriminants attribute is a type. The result
is a Boolean value which is True if the type has discriminants, and False
otherwise. The intended use of this attribute is in conjunction with generic
definitions. If the attribute is applied to a generic private type, it
indicates whether or not the corresponding actual type has discriminants.
Img
The Img attribute differs from Image in that it may be
applied to objects as well as types, in which case it gives the
Image for the subtype of the object. This is convenient for
debugging:
Put_Line ("X = " & X'Img);
has the same meaning as the more verbose:
Put_Line ("X = " & T'Image (X));
where T is the (sub)type of the object X.
Integer_Value
For every integer type S, S'Integer_Value denotes a
function with the following spec:
function S'Integer_Value (Arg : Universal_Fixed)
return S;
The value returned is the integer value V, such that
Arg = V * T'Small
where T is the type of Arg.
The effect is thus similar to first doing an unchecked conversion from
the fixed-point type to its corresponding implementation type, and then
converting the result to the target integer type. The difference is
that there are full range checks, to ensure that the result is in range.
This attribute is primarily intended for use in implementation of the
standard input-output functions for fixed-point values.
Large
The Large attribute is provided for compatibility with Ada 83. See
the Ada 83 reference manual for an exact description of the semantics of
this attribute.
Machine_Size
This attribute is identical to the Object_Size attribute. It is
provided for compatibility with the DEC Ada 83 attribute of this name.
Mantissa
The Mantissa attribute is provided for compatibility with Ada 83. See
the Ada 83 reference manual for an exact description of the semantics of
this attribute.
Max_Interrupt_Priority
Standard'Max_Interrupt_Priority (Standard is the only
permissible prefix), provides the same value as
System.Max_Interrupt_Priority.
Max_Priority
Standard'Max_Priority (Standard is the only permissible
prefix) provides the same value as System.Max_Priority.
Maximum_Alignment
Standard'Maximum_Alignment (Standard is the only
permissible prefix) provides the maximum useful alignment value for the
target. This is a static value that can be used to specify the alignment
for an object, guaranteeing that it is properly aligned in all
cases.
Mechanism_Code
function'Mechanism_Code yields an integer code for the
mechanism used for the result of function, and
subprogram'Mechanism_Code (n) yields the mechanism
used for formal parameter number n (a static integer value with 1
meaning the first parameter) of subprogram. The code returned is:
- 1
- by copy (value)
- 2
- by reference
- 3
- by descriptor (default descriptor class)
- 4
- by descriptor (UBS: unaligned bit string)
- 5
- by descriptor (UBSB: aligned bit string with arbitrary bounds)
- 6
- by descriptor (UBA: unaligned bit array)
- 7
- by descriptor (S: string, also scalar access type parameter)
- 8
- by descriptor (SB: string with arbitrary bounds)
- 9
- by descriptor (A: contiguous array)
- 10
- by descriptor (NCA: non-contiguous array)
Values from 3 through 10 are only relevant to Digital OpenVMS implementations.
Null_Parameter
A reference T'Null_Parameter denotes an imaginary object of
type or subtype T allocated at machine address zero. The attribute
is allowed only as the default expression of a formal parameter, or as
an actual expression of a subprogram call. In either case, the
subprogram must be imported.
The identity of the object is represented by the address zero in the
argument list, independent of the passing mechanism (explicit or
default).
This capability is needed to specify that a zero address should be
passed for a record or other composite object passed by reference.
There is no way of indicating this without the Null_Parameter
attribute.
Object_Size
The size of an object is not necessarily the same as the size of the type
of an object. This is because by default object sizes are increased to be
a multiple of the alignment of the object. For example,
Natural'Size is
31, but by default objects of type Natural will have a size of 32 bits.
Similarly, a record containing an integer and a character:
type Rec is record
I : Integer;
C : Character;
end record;
will have a size of 40 (that is Rec'Size will be 40. The
alignment will be 4, because of the
integer field, and so the default size of record objects for this type
will be 64 (8 bytes).
The type'Object_Size attribute
has been added to GNAT to allow the
default object size of a type to be easily determined. For example,
Natural'Object_Size is 32, and
Rec'Object_Size (for the record type in the above example) will be
64. Note also that, unlike the situation with the
Size attribute as defined in the Ada RM, the
Object_Size attribute can be specified individually
for different subtypes. For example:
type R is new Integer;
subtype R1 is R range 1 .. 10;
subtype R2 is R range 1 .. 10;
for R2'Object_Size use 8;
In this example, R'Object_Size and R1'Object_Size are both
32 since the default object size for a subtype is the same as the object size
for the parent subtype. This means that objects of type R
or R1 will
by default be 32 bits (four bytes). But objects of type
R2 will be only
8 bits (one byte), since R2'Object_Size has been set to 8.
Passed_By_Reference
type'Passed_By_Reference for any subtype type returns
a value of type Boolean value that is True if the type is
normally passed by reference and False if the type is normally
passed by copy in calls. For scalar types, the result is always False
and is static. For non-scalar types, the result is non-static.
Range_Length
type'Range_Length for any discrete type type yields
the number of values represented by the subtype (zero for a null
range). The result is static for static subtypes. Range_Length
applied to the index subtype of a one dimensional array always gives the
same result as Range applied to the array itself.
Safe_Emax
The Safe_Emax attribute is provided for compatibility with Ada 83. See
the Ada 83 reference manual for an exact description of the semantics of
this attribute.
Safe_Large
The Safe_Large attribute is provided for compatibility with Ada 83. See
the Ada 83 reference manual for an exact description of the semantics of
this attribute.
Small
The Small attribute is defined in Ada 95 only for fixed-point types.
GNAT also allows this attribute to be applied to floating-point types
for compatibility with Ada 83. See
the Ada 83 reference manual for an exact description of the semantics of
this attribute when applied to floating-point types.
Storage_Unit
Standard'Storage_Unit (Standard is the only permissible
prefix) provides the same value as System.Storage_Unit.
Target_Name
Standard'Target_Name (Standard is the only permissible
prefix) provides a static string value that identifies the target
for the current compilation. For GCC implementations, this is the
standard gcc target name without the terminating slash (for
example, GNAT 5.0 on windows yields "i586-pc-mingw32msv").
Tick
Standard'Tick (Standard is the only permissible prefix)
provides the same value as System.Tick,
To_Address
The System'To_Address
(System is the only permissible prefix)
denotes a function identical to
System.Storage_Elements.To_Address except that
it is a static attribute. This means that if its argument is
a static expression, then the result of the attribute is a
static expression. The result is that such an expression can be
used in contexts (e.g. preelaborable packages) which require a
static expression and where the function call could not be used
(since the function call is always non-static, even if its
argument is static).
Type_Class
type'Type_Class for any type or subtype type yields
the value of the type class for the full type of type. If
type is a generic formal type, the value is the value for the
corresponding actual subtype. The value of this attribute is of type
System.Aux_DEC.Type_Class, which has the following definition:
type Type_Class is
(Type_Class_Enumeration,
Type_Class_Integer,
Type_Class_Fixed_Point,
Type_Class_Floating_Point,
Type_Class_Array,
Type_Class_Record,
Type_Class_Access,
Type_Class_Task,
Type_Class_Address);
Protected types yield the value Type_Class_Task, which thus
applies to all concurrent types. This attribute is designed to
be compatible with the DEC Ada 83 attribute of the same name.
UET_Address
The UET_Address attribute can only be used for a prefix which
denotes a library package. It yields the address of the unit exception
table when zero cost exception handling is used. This attribute is
intended only for use within the GNAT implementation. See the unit
Ada.Exceptions in files a-except.ads and a-except.adb
for details on how this attribute is used in the implementation.
Unconstrained_Array
The Unconstrained_Array attribute can be used with a prefix that
denotes any type or subtype. It is a static attribute that yields
True if the prefix designates an unconstrained array,
and False otherwise. In a generic instance, the result is
still static, and yields the result of applying this test to the
generic actual.
Universal_Literal_String
The prefix of Universal_Literal_String must be a named
number. The static result is the string consisting of the characters of
the number as defined in the original source. This allows the user
program to access the actual text of named numbers without intermediate
conversions and without the need to enclose the strings in quotes (which
would preclude their use as numbers). This is used internally for the
construction of values of the floating-point attributes from the file
ttypef.ads, but may also be used by user programs.
Unrestricted_Access
The Unrestricted_Access attribute is similar to Access
except that all accessibility and aliased view checks are omitted. This
is a user-beware attribute. It is similar to
Address, for which it is a desirable replacement where the value
desired is an access type. In other words, its effect is identical to
first applying the Address attribute and then doing an unchecked
conversion to a desired access type. In GNAT, but not necessarily in
other implementations, the use of static chains for inner level
subprograms means that Unrestricted_Access applied to a
subprogram yields a value that can be called as long as the subprogram
is in scope (normal Ada 95 accessibility rules restrict this usage).
It is possible to use Unrestricted_Access for any type, but care
must be excercised if it is used to create pointers to unconstrained
objects. In this case, the resulting pointer has the same scope as the
context of the attribute, and may not be returned to some enclosing
scope. For instance, a function cannot use Unrestricted_Access
to create a unconstrained pointer and then return that value to the
caller.
VADS_Size
The 'VADS_Size attribute is intended to make it easier to port
legacy code which relies on the semantics of 'Size as implemented
by the VADS Ada 83 compiler. GNAT makes a best effort at duplicating the
same semantic interpretation. In particular, 'VADS_Size applied
to a predefined or other primitive type with no Size clause yields the
Object_Size (for example, Natural'Size is 32 rather than 31 on
typical machines). In addition 'VADS_Size applied to an object
gives the result that would be obtained by applying the attribute to
the corresponding type.
Value_Size
type'Value_Size is the number of bits required to represent
a value of the given subtype. It is the same as type'Size,
but, unlike Size, may be set for non-first subtypes.
Wchar_T_Size
Standard'Wchar_T_Size (Standard is the only permissible
prefix) provides the size in bits of the C wchar_t type
primarily for constructing the definition of this type in
package Interfaces.C.
Word_Size
Standard'Word_Size (Standard is the only permissible
prefix) provides the value System.Word_Size.
3 Implementation Advice
The main text of the Ada 95 Reference Manual describes the required
behavior of all Ada 95 compilers, and the GNAT compiler conforms to
these requirements.
In addition, there are sections throughout the Ada 95
reference manual headed
by the phrase “implementation advice”. These sections are not normative,
i.e. they do not specify requirements that all compilers must
follow. Rather they provide advice on generally desirable behavior. You
may wonder why they are not requirements. The most typical answer is
that they describe behavior that seems generally desirable, but cannot
be provided on all systems, or which may be undesirable on some systems.
As far as practical, GNAT follows the implementation advice sections in
the Ada 95 Reference Manual. This chapter contains a table giving the
reference manual section number, paragraph number and several keywords
for each advice. Each entry consists of the text of the advice followed
by the GNAT interpretation of this advice. Most often, this simply says
“followed”, which means that GNAT follows the advice. However, in a
number of cases, GNAT deliberately deviates from this advice, in which
case the text describes what GNAT does and why.
1.1.3(20): Error Detection
If an implementation detects the use of an unsupported Specialized Needs
Annex feature at run time, it should raise Program_Error if
feasible.
|
Not relevant. All specialized needs annex features are either supported,
or diagnosed at compile time.
1.1.3(31): Child Units
|
If an implementation wishes to provide implementation-defined
extensions to the functionality of a language-defined library unit, it
should normally do so by adding children to the library unit.
|
Followed.
1.1.5(12): Bounded Errors
If an implementation detects a bounded error or erroneous
execution, it should raise Program_Error.
|
Followed in all cases in which the implementation detects a bounded
error or erroneous execution. Not all such situations are detected at
runtime.
2.8(16): Pragmas
|
Normally, implementation-defined pragmas should have no semantic effect
for error-free programs; that is, if the implementation-defined pragmas
are removed from a working program, the program should still be legal,
and should still have the same semantics.
|
The following implementation defined pragmas are exceptions to this
rule:
Abort_Defer- Affects semantics
Ada_83- Affects legality
Assert- Affects semantics
CPP_Class- Affects semantics
CPP_Constructor- Affects semantics
CPP_Virtual- Affects semantics
CPP_Vtable- Affects semantics
Debug- Affects semantics
Interface_Name- Affects semantics
Machine_Attribute- Affects semantics
Unimplemented_Unit- Affects legality
Unchecked_Union- Affects semantics
In each of the above cases, it is essential to the purpose of the pragma
that this advice not be followed. For details see the separate section
on implementation defined pragmas.
2.8(17-19): Pragmas
|
Normally, an implementation should not define pragmas that can
make an illegal program legal, except as follows:
|
A pragma used to complete a declaration, such as a pragma Import;
|
A pragma used to configure the environment by adding, removing, or
replacing library_items.
|
See response to paragraph 16 of this same section.
3.5.2(5): Alternative Character Sets
If an implementation supports a mode with alternative interpretations
for Character and Wide_Character, the set of graphic
characters of Character should nevertheless remain a proper
subset of the set of graphic characters of Wide_Character. Any
character set “localizations” should be reflected in the results of
the subprograms defined in the language-defined package
Characters.Handling (see A.3) available in such a mode. In a mode with
an alternative interpretation of Character, the implementation should
also support a corresponding change in what is a legal
identifier_letter.
|
Not all wide character modes follow this advice, in particular the JIS
and IEC modes reflect standard usage in Japan, and in these encoding,
the upper half of the Latin-1 set is not part of the wide-character
subset, since the most significant bit is used for wide character
encoding. However, this only applies to the external forms. Internally
there is no such restriction.
3.5.4(28): Integer Types
An implementation should support Long_Integer in addition to
Integer if the target machine supports 32-bit (or longer)
arithmetic. No other named integer subtypes are recommended for package
Standard. Instead, appropriate named integer subtypes should be
provided in the library package Interfaces (see B.2).
|
Long_Integer is supported. Other standard integer types are supported
so this advice is not fully followed. These types
are supported for convenient interface to C, and so that all hardware
types of the machine are easily available.
3.5.4(29): Integer Types
An implementation for a two's complement machine should support
modular types with a binary modulus up to System.Max_Int*2+2. An
implementation should support a non-binary modules up to Integer'Last.
|
Followed.
3.5.5(8): Enumeration Values
For the evaluation of a call on S'Pos for an enumeration
subtype, if the value of the operand does not correspond to the internal
code for any enumeration literal of its type (perhaps due to an
un-initialized variable), then the implementation should raise
Program_Error. This is particularly important for enumeration
types with noncontiguous internal codes specified by an
enumeration_representation_clause.
|
Followed.
3.5.7(17): Float Types
An implementation should support Long_Float in addition to
Float if the target machine supports 11 or more digits of
precision. No other named floating point subtypes are recommended for
package Standard. Instead, appropriate named floating point subtypes
should be provided in the library package Interfaces (see B.2).
|
Short_Float and Long_Long_Float are also provided. The
former provides improved compatibility with other implementations
supporting this type. The latter corresponds to the highest precision
floating-point type supported by the hardware. On most machines, this
will be the same as Long_Float, but on some machines, it will
correspond to the IEEE extended form. The notable case is all ia32
(x86) implementations, where Long_Long_Float corresponds to
the 80-bit extended precision format supported in hardware on this
processor. Note that the 128-bit format on SPARC is not supported,
since this is a software rather than a hardware format.
3.6.2(11): Multidimensional Arrays
An implementation should normally represent multidimensional arrays in
row-major order, consistent with the notation used for multidimensional
array aggregates (see 4.3.3). However, if a pragma Convention
(Fortran, ...) applies to a multidimensional array type, then
column-major order should be used instead (see B.5, “Interfacing with
Fortran”).
|
Followed.
9.6(30-31): Duration'Small
Whenever possible in an implementation, the value of Duration'Small
should be no greater than 100 microseconds.
|
Followed. (Duration'Small = 10**(−9)).
The time base for delay_relative_statements should be monotonic;
it need not be the same time base as used for Calendar.Clock.
|
Followed.
10.2.1(12): Consistent Representation
|
In an implementation, a type declared in a pre-elaborated package should
have the same representation in every elaboration of a given version of
the package, whether the elaborations occur in distinct executions of
the same program, or in executions of distinct programs or partitions
that include the given version.
|
Followed, except in the case of tagged types. Tagged types involve
implicit pointers to a local copy of a dispatch table, and these pointers
have representations which thus depend on a particular elaboration of the
package. It is not easy to see how it would be possible to follow this
advice without severely impacting efficiency of execution.
11.4.1(19): Exception Information
Exception_Message by default and Exception_Information
should produce information useful for
debugging. Exception_Message should be short, about one
line. Exception_Information can be long. Exception_Message
should not include the
Exception_Name. Exception_Information should include both
the Exception_Name and the Exception_Message.
|
Followed. For each exception that doesn't have a specified
Exception_Message, the compiler generates one containing the location
of the raise statement. This location has the form “file:line”, where
file is the short file name (without path information) and line is the line
number in the file. Note that in the case of the Zero Cost Exception
mechanism, these messages become redundant with the Exception_Information that
contains a full backtrace of the calling sequence, so they are disabled.
To disable explicitly the generation of the source location message, use the
Pragma Discard_Names.
11.5(28): Suppression of Checks
|
The implementation should minimize the code executed for checks that
have been suppressed.
|
Followed.
13.1 (21-24): Representation Clauses
|
The recommended level of support for all representation items is
qualified as follows:
|
|
An implementation need not support representation items containing
non-static expressions, except that an implementation should support a
representation item for a given entity if each non-static expression in
the representation item is a name that statically denotes a constant
declared before the entity.
|
Followed. GNAT does not support non-static expressions in representation
clauses unless they are constants declared before the entity. For
example:
X : Some_Type;
for X'Address use To_address (16#2000#);
will be rejected, since the To_Address expression is non-static. Instead
write:
X_Address : constant Address : = To_Address (16#2000#);
X : Some_Type;
for X'Address use X_Address;
An implementation need not support a specification for the Size
for a given composite subtype, nor the size or storage place for an
object (including a component) of a given composite subtype, unless the
constraints on the subtype and its composite subcomponents (if any) are
all static constraints.
|
Followed. Size Clauses are not permitted on non-static components, as
described above.
|
An aliased component, or a component whose type is by-reference, should
always be allocated at an addressable location.
|
Followed.
13.2(6-8): Packed Types
|
If a type is packed, then the implementation should try to minimize
storage allocated to objects of the type, possibly at the expense of
speed of accessing components, subject to reasonable complexity in
addressing calculations.
|
The recommended level of support pragma Pack is:
For a packed record type, the components should be packed as tightly as
possible subject to the Sizes of the component subtypes, and subject to
any record_representation_clause that applies to the type; the
implementation may, but need not, reorder components or cross aligned
word boundaries to improve the packing. A component whose Size is
greater than the word size may be allocated an integral number of words.
|
Followed. Tight packing of arrays is supported for all component sizes
up to 64-bits. If the array component size is 1 (that is to say, if
the component is a boolean type or an enumeration type with two values)
then values of the type are implicitly initialized to zero. This
happens both for objects of the packed type, and for objects that have a
subcomponent of the packed type.
|
An implementation should support Address clauses for imported
subprograms.
|
Followed.
13.3(14-19): Address Clauses
For an array X, X'Address should point at the first
component of the array, and not at the array bounds.
|
Followed.
The recommended level of support for the Address attribute is:
X'Address should produce a useful result if X is an
object that is aliased or of a by-reference type, or is an entity whose
Address has been specified.
|
Followed. A valid address will be produced even if none of those
conditions have been met. If necessary, the object is forced into
memory to ensure the address is valid.
An implementation should support Address clauses for imported
subprograms.
|
Followed.
|
Objects (including subcomponents) that are aliased or of a by-reference
type should be allocated on storage element boundaries.
|
Followed.
If the Address of an object is specified, or it is imported or exported,
then the implementation should not perform optimizations based on
assumptions of no aliases.
|
Followed.
13.3(29-35): Alignment Clauses
The recommended level of support for the Alignment attribute for
subtypes is:
An implementation should support specified Alignments that are factors
and multiples of the number of storage elements per word, subject to the
following:
|
Followed.
An implementation need not support specified Alignments for
combinations of Sizes and Alignments that cannot be easily
loaded and stored by available machine instructions.
|
Followed.
An implementation need not support specified Alignments that are
greater than the maximum Alignment the implementation ever returns by
default.
|
Followed.
The recommended level of support for the Alignment attribute for
objects is:
Same as above, for subtypes, but in addition:
|
Followed.
For stand-alone library-level objects of statically constrained
subtypes, the implementation should support all Alignments
supported by the target linker. For example, page alignment is likely to
be supported for such objects, but not for subtypes.
|
Followed.
13.3(42-43): Size Clauses
The recommended level of support for the Size attribute of
objects is:
A Size clause should be supported for an object if the specified
Size is at least as large as its subtype's Size, and
corresponds to a size in storage elements that is a multiple of the
object's Alignment (if the Alignment is nonzero).
|
Followed.
13.3(50-56): Size Clauses
If the Size of a subtype is specified, and allows for efficient
independent addressability (see 9.10) on the target architecture, then
the Size of the following objects of the subtype should equal the
Size of the subtype:
Aliased objects (including components).
|
Followed.
Size clause on a composite subtype should not affect the
internal layout of components.
|
Followed.
The recommended level of support for the Size attribute of subtypes is:
|
The Size (if not specified) of a static discrete or fixed point
subtype should be the number of bits needed to represent each value
belonging to the subtype using an unbiased representation, leaving space
for a sign bit only if the subtype contains negative values. If such a
subtype is a first subtype, then an implementation should support a
specified Size for it that reflects this representation.
|
Followed.
For a subtype implemented with levels of indirection, the Size
should include the size of the pointers, but not the size of what they
point at.
|
Followed.
13.3(71-73): Component Size Clauses
The recommended level of support for the Component_Size
attribute is:
|
An implementation need not support specified Component_Sizes that are
less than the Size of the component subtype.
|
Followed.
An implementation should support specified Component_Sizes that
are factors and multiples of the word size. For such
Component_Sizes, the array should contain no gaps between
components. For other Component_Sizes (if supported), the array
should contain no gaps between components when packing is also
specified; the implementation should forbid this combination in cases
where it cannot support a no-gaps representation.
|
Followed.
13.4(9-10): Enumeration Representation Clauses
|
The recommended level of support for enumeration representation clauses
is:
An implementation need not support enumeration representation clauses
for boolean types, but should at minimum support the internal codes in
the range System.Min_Int.System.Max_Int.
|
Followed.
13.5.1(17-22): Record Representation Clauses
The recommended level of support for
record_representation_clauses is:
An implementation should support storage places that can be extracted
with a load, mask, shift sequence of machine code, and set with a load,
shift, mask, store sequence, given the available machine instructions
and run-time model.
|
Followed.
A storage place should be supported if its size is equal to the
Size of the component subtype, and it starts and ends on a
boundary that obeys the Alignment of the component subtype.
|
Followed.
If the default bit ordering applies to the declaration of a given type,
then for a component whose subtype's Size is less than the word
size, any storage place that does not cross an aligned word boundary
should be supported.
|
Followed.
|
An implementation may reserve a storage place for the tag field of a
tagged type, and disallow other components from overlapping that place.
|
Followed. The storage place for the tag field is the beginning of the tagged
record, and its size is Address'Size. GNAT will reject an explicit component
clause for the tag field.
An implementation need not support a component_clause for a
component of an extension part if the storage place is not after the
storage places of all components of the parent type, whether or not
those storage places had been specified.
|
Followed. The above advice on record representation clauses is followed,
and all mentioned features are implemented.
13.5.2(5): Storage Place Attributes
|
If a component is represented using some form of pointer (such as an
offset) to the actual data of the component, and this data is contiguous
with the rest of the object, then the storage place attributes should
reflect the place of the actual data, not the pointer. If a component is
allocated discontinuously from the rest of the object, then a warning
should be generated upon reference to one of its storage place
attributes.
|
Followed. There are no such components in GNAT.
13.5.3(7-8): Bit Ordering
|
The recommended level of support for the non-default bit ordering is:
|
If Word_Size = Storage_Unit, then the implementation
should support the non-default bit ordering in addition to the default
bit ordering.
|
Followed. Word size does not equal storage size in this implementation.
Thus non-default bit ordering is not supported.
13.7(37): Address as Private
Address should be of a private type.
|
Followed.
13.7.1(16): Address Operations
Operations in System and its children should reflect the target
environment semantics as closely as is reasonable. For example, on most
machines, it makes sense for address arithmetic to “wrap around”.
Operations that do not make sense should raise Program_Error.
|
Followed. Address arithmetic is modular arithmetic that wraps around. No
operation raises Program_Error, since all operations make sense.
13.9(14-17): Unchecked Conversion
The Size of an array object should not include its bounds; hence,
the bounds should not be part of the converted data.
|
Followed.
|
The implementation should not generate unnecessary run-time checks to
ensure that the representation of S is a representation of the
target type. It should take advantage of the permission to return by
reference when possible. Restrictions on unchecked conversions should be
avoided unless required by the target environment.
|
Followed. There are no restrictions on unchecked conversion. A warning is
generated if the source and target types do not have the same size since
the semantics in this case may be target dependent.
|
The recommended level of support for unchecked conversions is:
|
|
Unchecked conversions should be supported and should be reversible in
the cases where this clause defines the result. To enable meaningful use
of unchecked conversion, a contiguous representation should be used for
elementary subtypes, for statically constrained array subtypes whose
component subtype is one of the subtypes described in this paragraph,
and for record subtypes without discriminants whose component subtypes
are described in this paragraph.
|
Followed.
13.11(23-25): Implicit Heap Usage
|
An implementation should document any cases in which it dynamically
allocates heap storage for a purpose other than the evaluation of an
allocator.
|
Followed, the only other points at which heap storage is dynamically
allocated are as follows:
- At initial elaboration time, to allocate dynamically sized global
objects.
- To allocate space for a task when a task is created.
- To extend the secondary stack dynamically when needed. The secondary
stack is used for returning variable length results.
|
A default (implementation-provided) storage pool for an
access-to-constant type should not have overhead to support deallocation of
individual objects.
|
Followed.
|
A storage pool for an anonymous access type should be created at the
point of an allocator for the type, and be reclaimed when the designated
object becomes inaccessible.
|
Followed.
13.11.2(17): Unchecked De-allocation
For a standard storage pool, Free should actually reclaim the
storage.
|
Followed.
13.13.2(17): Stream Oriented Attributes
If a stream element is the same size as a storage element, then the
normal in-memory representation should be used by Read and
Write for scalar objects. Otherwise, Read and Write
should use the smallest number of stream elements needed to represent
all values in the base range of the scalar type.
|
Followed. By default, GNAT uses the interpretation suggested by AI-195,
which specifies using the size of the first subtype.
However, such an implementation is based on direct binary
representations and is therefore target- and endianness-dependent.
To address this issue, GNAT also supplies an alternate implementation
of the stream attributes Read and Write,
which uses the target-independent XDR standard representation
for scalar types.
The XDR implementation is provided as an alternative body of the
System.Stream_Attributes package, in the file
s-strxdr.adb in the GNAT library.
There is no s-strxdr.ads file.
In order to install the XDR implementation, do the following:
- Replace the default implementation of the
System.Stream_Attributes package with the XDR implementation.
For example on a Unix platform issue the commands:
$ mv s-stratt.adb s-strold.adb
$ mv s-strxdr.adb s-stratt.adb
- Rebuild the GNAT run-time library as documented in the
GNAT User's Guide
A.1(52): Names of Predefined Numeric Types
|
If an implementation provides additional named predefined integer types,
then the names should end with Integer as in
Long_Integer. If an implementation provides additional named
predefined floating point types, then the names should end with
Float as in Long_Float.
|
Followed.
A.3.2(49): Ada.Characters.Handling
If an implementation provides a localized definition of Character
or Wide_Character, then the effects of the subprograms in
Characters.Handling should reflect the localizations. See also
3.5.2.
|
Followed. GNAT provides no such localized definitions.
A.4.4(106): Bounded-Length String Handling
|
Bounded string objects should not be implemented by implicit pointers
and dynamic allocation.
|
Followed. No implicit pointers or dynamic allocation are used.
A.5.2(46-47): Random Number Generation
Any storage associated with an object of type Generator should be
reclaimed on exit from the scope of the object.
|
Followed.
If the generator period is sufficiently long in relation to the number
of distinct initiator values, then each possible value of
Initiator passed to Reset should initiate a sequence of
random numbers that does not, in a practical sense, overlap the sequence
initiated by any other value. If this is not possible, then the mapping
between initiator values and generator states should be a rapidly
varying function of the initiator value.
|
Followed. The generator period is sufficiently long for the first
condition here to hold true.
A.10.7(23): Get_Immediate
The Get_Immediate procedures should be implemented with
unbuffered input. For a device such as a keyboard, input should be
available if a key has already been typed, whereas for a disk
file, input should always be available except at end of file. For a file
associated with a keyboard-like device, any line-editing features of the
underlying operating system should be disabled during the execution of
Get_Immediate.
|
Followed on all targets except VxWorks. For VxWorks, there is no way to
provide this functionality that does not result in the input buffer being
flushed before the Get_Immediate call. A special unit
Interfaces.Vxworks.IO is provided that contains routines to enable
this functionality.
B.1(39-41): Pragma Export
If an implementation supports pragma Export to a given language,
then it should also allow the main subprogram to be written in that
language. It should support some mechanism for invoking the elaboration
of the Ada library units included in the system, and for invoking the
finalization of the environment task. On typical systems, the
recommended mechanism is to provide two subprograms whose link names are
adainit and adafinal. adainit should contain the
elaboration code for library units. adafinal should contain the
finalization code. These subprograms should have no effect the second
and subsequent time they are called.
|
Followed.
Automatic elaboration of pre-elaborated packages should be
provided when pragma Export is supported.
|
Followed when the main program is in Ada. If the main program is in a
foreign language, then
adainit must be called to elaborate pre-elaborated
packages.
For each supported convention L other than Intrinsic, an
implementation should support Import and Export pragmas
for objects of L-compatible types and for subprograms, and pragma
Convention for L-eligible types and for subprograms,
presuming the other language has corresponding features. Pragma
Convention need not be supported for scalar types.
|
Followed.
B.2(12-13): Package Interfaces
For each implementation-defined convention identifier, there should be a
child package of package Interfaces with the corresponding name. This
package should contain any declarations that would be useful for
interfacing to the language (implementation) represented by the
convention. Any declarations useful for interfacing to any language on
the given hardware architecture should be provided directly in
Interfaces.
|
Followed. An additional package not defined
in the Ada 95 Reference Manual is Interfaces.CPP, used
for interfacing to C++.
|
An implementation supporting an interface to C, COBOL, or Fortran should
provide the corresponding package or packages described in the following
clauses.
|
Followed. GNAT provides all the packages described in this section.
B.3(63-71): Interfacing with C
|
An implementation should support the following interface correspondences
between Ada and C.
|
Followed.
|
An Ada procedure corresponds to a void-returning C function.
|
Followed.
|
An Ada function corresponds to a non-void C function.
|
Followed.
An Ada in scalar parameter is passed as a scalar argument to a C
function.
|
Followed.
An Ada in parameter of an access-to-object type with designated
type T is passed as a t* argument to a C function,
where t is the C type corresponding to the Ada type T.
|
Followed.
An Ada access T parameter, or an Ada out or in out
parameter of an elementary type T, is passed as a t*
argument to a C function, where t is the C type corresponding to
the Ada type T. In the case of an elementary out or
in out parameter, a pointer to a temporary copy is used to
preserve by-copy semantics.
|
Followed.
An Ada parameter of a record type T, of any mode, is passed as a
t* argument to a C function, where t is the C
structure corresponding to the Ada type T.
|
Followed. This convention may be overridden by the use of the C_Pass_By_Copy
pragma, or Convention, or by explicitly specifying the mechanism for a given
call using an extended import or export pragma.
An Ada parameter of an array type with component type T, of any
mode, is passed as a t* argument to a C function, where
t is the C type corresponding to the Ada type T.
|
Followed.
|
An Ada parameter of an access-to-subprogram type is passed as a pointer
to a C function whose prototype corresponds to the designated
subprogram's specification.
|
Followed.
B.4(95-98): Interfacing with COBOL
|
An Ada implementation should support the following interface
correspondences between Ada and COBOL.
|
Followed.
|
An Ada access T parameter is passed as a BY REFERENCE data item of
the COBOL type corresponding to T.
|
Followed.
|
An Ada in scalar parameter is passed as a BY CONTENT data item of
the corresponding COBOL type.
|
Followed.
|
Any other Ada parameter is passed as a BY REFERENCE data item of the
COBOL type corresponding to the Ada parameter type; for scalars, a local
copy is used if necessary to ensure by-copy semantics.
|
Followed.
B.5(22-26): Interfacing with Fortran
|
An Ada implementation should support the following interface
correspondences between Ada and Fortran:
|
Followed.
|
An Ada procedure corresponds to a Fortran subroutine.
|
Followed.
|
An Ada function corresponds to a Fortran function.
|
Followed.
|
An Ada parameter of an elementary, array, or record type T is
passed as a T argument to a Fortran procedure, where T is
the Fortran type corresponding to the Ada type T, and where the
INTENT attribute of the corresponding dummy argument matches the Ada
formal parameter mode; the Fortran implementation's parameter passing
conventions are used. For elementary types, a local copy is used if
necessary to ensure by-copy semantics.
|
Followed.
|
An Ada parameter of an access-to-subprogram type is passed as a
reference to a Fortran procedure whose interface corresponds to the
designated subprogram's specification.
|
Followed.
C.1(3-5): Access to Machine Operations
|
The machine code or intrinsic support should allow access to all
operations normally available to assembly language programmers for the
target environment, including privileged instructions, if any.
|
Followed.
The interfacing pragmas (see Annex B) should support interface to
assembler; the default assembler should be associated with the
convention identifier Assembler.
|
Followed.
|
If an entity is exported to assembly language, then the implementation
should allocate it at an addressable location, and should ensure that it
is retained by the linking process, even if not otherwise referenced
from the Ada code. The implementation should assume that any call to a
machine code or assembler subprogram is allowed to read or update every
object that is specified as exported.
|
Followed.
C.1(10-16): Access to Machine Operations
|
The implementation should ensure that little or no overhead is
associated with calling intrinsic and machine-code subprograms.
|
Followed for both intrinsics and machine-code subprograms.
|
It is recommended that intrinsic subprograms be provided for convenient
access to any machine operations that provide special capabilities or
efficiency and that are not otherwise available through the language
constructs.
|
Followed. A full set of machine operation intrinsic subprograms is provided.
|
Atomic read-modify-write operations—e.g., test and set, compare and
swap, decrement and test, enqueue/dequeue.
|
Followed on any target supporting such operations.
|
Standard numeric functions—e.g., sin, log.
|
Followed on any target supporting such operations.
|
String manipulation operations—e.g., translate and test.
|
Followed on any target supporting such operations.
|
Vector operations—e.g., compare vector against thresholds.
|
Followed on any target supporting such operations.
|
Direct operations on I/O ports.
|
Followed on any target supporting such operations.
C.3(28): Interrupt Support
If the Ceiling_Locking policy is not in effect, the
implementation should provide means for the application to specify which
interrupts are to be blocked during protected actions, if the underlying
system allows for a finer-grain control of interrupt blocking.
|
Followed. The underlying system does not allow for finer-grain control
of interrupt blocking.
C.3.1(20-21): Protected Procedure Handlers
|
Whenever possible, the implementation should allow interrupt handlers to
be called directly by the hardware.
|
Followed on any target where the underlying operating system permits
such direct calls.
|
Whenever practical, violations of any
implementation-defined restrictions should be detected before run time.
|
Followed. Compile time warnings are given when possible.
C.3.2(25): Package Interrupts
If implementation-defined forms of interrupt handler procedures are
supported, such as protected procedures with parameters, then for each
such form of a handler, a type analogous to Parameterless_Handler
should be specified in a child package of Interrupts, with the
same operations as in the predefined package Interrupts.
|
Followed.
C.4(14): Pre-elaboration Requirements
|
It is recommended that pre-elaborated packages be implemented in such a
way that there should be little or no code executed at run time for the
elaboration of entities not already covered by the Implementation
Requirements.
|
Followed. Executable code is generated in some cases, e.g. loops
to initialize large arrays.
C.5(8): Pragma Discard_Names
|
If the pragma applies to an entity, then the implementation should
reduce the amount of storage used for storing names associated with that
entity.
|
Followed.
C.7.2(30): The Package Task_Attributes
|
Some implementations are targeted to domains in which memory use at run
time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first N
attribute objects, and the heap for the others. In the latter case,
N should be documented.
|
Not followed. This implementation is not targeted to such a domain.
D.3(17): Locking Policies
|
The implementation should use names that end with _Locking for
locking policies defined by the implementation.
|
Followed. A single implementation-defined locking policy is defined,
whose name (Inheritance_Locking) follows this suggestion.
D.4(16): Entry Queuing Policies
|
Names that end with _Queuing should be used
for all implementation-defined queuing policies.
|
Followed. No such implementation-defined queuing policies exist.
D.6(9-10): Preemptive Abort
Even though the abort_statement is included in the list of
potentially blocking operations (see 9.5.1), it is recommended that this
statement be implemented in a way that never requires the task executing
the abort_statement to block.
|
Followed.
|
On a multi-processor, the delay associated with aborting a task on
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
|
Followed.
D.7(21): Tasking Restrictions
|
When feasible, the implementation should take advantage of the specified
restrictions to produce a more efficient implementation.
|
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
of restrictions are specified. See pragma Ravenscar and pragma
Restricted_Run_Time for more details.
D.8(47-49): Monotonic Time
When appropriate, implementations should provide configuration
mechanisms to change the value of Tick.
|
Such configuration mechanisms are not appropriate to this implementation
and are thus not supported.
It is recommended that Calendar.Clock and Real_Time.Clock
be implemented as transformations of the same time base.
|
Followed.
It is recommended that the best time base which exists in
the underlying system be available to the application through
Clock. Best may mean highest accuracy or largest range.
|
Followed.
E.5(28-29): Partition Communication Subsystem
|
Whenever possible, the PCS on the called partition should allow for
multiple tasks to call the RPC-receiver with different messages and
should allow them to block until the corresponding subprogram body
returns.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
The Write operation on a stream of type Params_Stream_Type
should raise Storage_Error if it runs out of space trying to
write the Item into the stream.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
F(7): COBOL Support
If COBOL (respectively, C) is widely supported in the target
environment, implementations supporting the Information Systems Annex
should provide the child package Interfaces.COBOL (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of COBOL (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
F.1(2): Decimal Radix Support
|
Packed decimal should be used as the internal representation for objects
of subtype S when S'Machine_Radix = 10.
|
Not followed. GNAT ignores S'Machine_Radix and always uses binary
representations.
G: Numerics
If Fortran (respectively, C) is widely supported in the target
environment, implementations supporting the Numerics Annex
should provide the child package Interfaces.Fortran (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of Fortran (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
G.1.1(56-58): Complex Types
|
Because the usual mathematical meaning of multiplication of a complex
operand and a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
|
Not followed.
Similarly, because the usual mathematical meaning of addition of a
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
complex addition. In implementations in which the Signed_Zeros
attribute of the component type is True (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
|
Not followed.
Implementations in which Real'Signed_Zeros is True should
attempt to provide a rational treatment of the signs of zero results and
result components. As one example, the result of the Argument
function should have the sign of the imaginary component of the
parameter X when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
of the Compose_From_Polar function should be the same as
(respectively, the opposite of) that of the Argument parameter when that
parameter has a value of zero and the Modulus parameter has a
nonnegative (respectively, negative) value.
|
Followed.
G.1.2(49): Complex Elementary Functions
Implementations in which Complex_Types.Real'Signed_Zeros is
True should attempt to provide a rational treatment of the signs
of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
a parameter component at the origin, or is always positive or always
negative.
|
Followed.
G.2.4(19): Accuracy Requirements
The versions of the forward trigonometric functions without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain. For the same reason, the
version of Log without a Base parameter should not be
implemented by calling the corresponding version with a Base
parameter of Numerics.e.
|
Followed.
G.2.6(15): Complex Arithmetic Accuracy
The version of the Compose_From_Polar function without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain.
|
Followed.
4 Implementation Defined Characteristics
In addition to the implementation dependent pragmas and attributes, and
the implementation advice, there are a number of other features of Ada
95 that are potentially implementation dependent. These are mentioned
throughout the Ada 95 Reference Manual, and are summarized in annex M.
A requirement for conforming Ada compilers is that they provide
documentation describing how the implementation deals with each of these
issues. In this chapter, you will find each point in annex M listed
followed by a description in italic font of how GNAT
handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation
dependent features in your programs if portability to other compilers
and other operating systems is an important consideration. The numbers
in each section below correspond to the paragraph number in the Ada 95
Reference Manual.
|
2. Whether or not each recommendation given in Implementation
Advice is followed. See 1.1.2(37).
|
See Implementation Advice.
|
3. Capacity limitations of the implementation. See 1.1.3(3).
|
The complexity of programs that can be processed is limited only by the
total amount of available virtual memory, and disk space for the
generated object files.
|
4. Variations from the standard that are impractical to avoid
given the implementation's execution environment. See 1.1.3(6).
|
There are no variations from the standard.
5. Which code_statements cause external
interactions. See 1.1.3(10).
|
Any code_statement can potentially cause external "cartouche" border="1">
If implementation-defined forms of interrupt handler procedures are
supported, such as protected procedures with parameters, then for each
such form of a handler, a type analogous to Parameterless_Handler
should be specified in a child package of Interrupts, with the
same operations as in the predefined package Interrupts.
|
Followed.
C.4(14): Pre-elaboration Requirements
|
It is recommended that pre-elaborated packages be implemented in such a
way that there should be little or no code executed at run time for the
elaboration of entities not already covered by the Implementation
Requirements.
|
Followed. Executable code is generated in some cases, e.g. loops
to initialize large arrays.
C.5(8): Pragma Discard_Names
|
If the pragma applies to an entity, then the implementation should
reduce the amount of storage used for storing names associated with that
entity.
|
Followed.
C.7.2(30): The Package Task_Attributes
|
Some implementations are targeted to domains in which memory use at run
time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first N
attribute objects, and the heap for the others. In the latter case,
N should be documented.
|
Not followed. This implementation is not targeted to such a domain.
D.3(17): Locking Policies
|
The implementation should use names that end with _Locking for
locking policies defined by the implementation.
|
Followed. A single implementation-defined locking policy is defined,
whose name (Inheritance_Locking) follows this suggestion.
D.4(16): Entry Queuing Policies
|
Names that end with _Queuing should be used
for all implementation-defined queuing policies.
|
Followed. No such implementation-defined queuing policies exist.
D.6(9-10): Preemptive Abort
Even though the abort_statement is included in the list of
potentially blocking operations (see 9.5.1), it is recommended that this
statement be implemented in a way that never requires the task executing
the abort_statement to block.
|
Followed.
|
On a multi-processor, the delay associated with aborting a task on
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
|
Followed.
D.7(21): Tasking Restrictions
|
When feasible, the implementation should take advantage of the specified
restrictions to produce a more efficient implementation.
|
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
of restrictions are specified. See pragma Ravenscar and pragma
Restricted_Run_Time for more details.
D.8(47-49): Monotonic Time
When appropriate, implementations should provide configuration
mechanisms to change the value of Tick.
|
Such configuration mechanisms are not appropriate to this implementation
and are thus not supported.
It is recommended that Calendar.Clock and Real_Time.Clock
be implemented as transformations of the same time base.
|
Followed.
It is recommended that the best time base which exists in
the underlying system be available to the application through
Clock. Best may mean highest accuracy or largest range.
|
Followed.
E.5(28-29): Partition Communication Subsystem
|
Whenever possible, the PCS on the called partition should allow for
multiple tasks to call the RPC-receiver with different messages and
should allow them to block until the corresponding subprogram body
returns.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
The Write operation on a stream of type Params_Stream_Type
should raise Storage_Error if it runs out of space trying to
write the Item into the stream.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
F(7): COBOL Support
If COBOL (respectively, C) is widely supported in the target
environment, implementations supporting the Information Systems Annex
should provide the child package Interfaces.COBOL (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of COBOL (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
F.1(2): Decimal Radix Support
|
Packed decimal should be used as the internal representation for objects
of subtype S when S'Machine_Radix = 10.
|
Not followed. GNAT ignores S'Machine_Radix and always uses binary
representations.
G: Numerics
If Fortran (respectively, C) is widely supported in the target
environment, implementations supporting the Numerics Annex
should provide the child package Interfaces.Fortran (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of Fortran (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
G.1.1(56-58): Complex Types
|
Because the usual mathematical meaning of multiplication of a complex
operand and a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
|
Not followed.
Similarly, because the usual mathematical meaning of addition of a
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
complex addition. In implementations in which the Signed_Zeros
attribute of the component type is True (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
|
Not followed.
Implementations in which Real'Signed_Zeros is True should
attempt to provide a rational treatment of the signs of zero results and
result components. As one example, the result of the Argument
function should have the sign of the imaginary component of the
parameter X when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
of the Compose_From_Polar function should be the same as
(respectively, the opposite of) that of the Argument parameter when that
parameter has a value of zero and the Modulus parameter has a
nonnegative (respectively, negative) value.
|
Followed.
G.1.2(49): Complex Elementary Functions
Implementations in which Complex_Types.Real'Signed_Zeros is
True should attempt to provide a rational treatment of the signs
of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
a parameter component at the origin, or is always positive or always
negative.
|
Followed.
G.2.4(19): Accuracy Requirements
The versions of the forward trigonometric functions without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain. For the same reason, the
version of Log without a Base parameter should not be
implemented by calling the corresponding version with a Base
parameter of Numerics.e.
|
Followed.
G.2.6(15): Complex Arithmetic Accuracy
The version of the Compose_From_Polar function without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain.
|
Followed.
4 Implementation Defined Characteristics
In addition to the implementation dependent pragmas and attributes, and
the implementation advice, there are a number of other features of Ada
95 that are potentially implementation dependent. These are mentioned
throughout the Ada 95 Reference Manual, and are summarized in annex M.
A requirement for conforming Ada compilers is that they provide
documentation describing how the implementation deals with each of these
issues. In this chapter, you will find each point in annex M listed
followed by a description in italic font of how GNAT
handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation
dependent features in your programs if portability to other compilers
and other operating systems is an important consideration. The numbers
in each section below correspond to the paragraph number in the Ada 95
Reference Manual.
|
2. Whether or not each recommendation given in Implementation
Advice is followed. See 1.1.2(37).
|
See Implementation Advice.
|
3. Capacity limitations of the implementation. See 1.1.3(3).
|
The complexity of programs that can be processed is limited only by the
total amount of available virtual memory, and disk space for the
generated object files.
|
4. Variations from the standard that are impractical to avoid
given the implementation's execution environment. See 1.1.3(6).
|
There are no variations from the standard.
5. Which code_statements cause external
interactions. See 1.1.3(10).
|
Any code_statement can potentially cause external "cartouche" border="1">
If implementation-defined forms of interrupt handler procedures are
supported, such as protected procedures with parameters, then for each
such form of a handler, a type analogous to Parameterless_Handler
should be specified in a child package of Interrupts, with the
same operations as in the predefined package Interrupts.
|
Followed.
C.4(14): Pre-elaboration Requirements
|
It is recommended that pre-elaborated packages be implemented in such a
way that there should be little or no code executed at run time for the
elaboration of entities not already covered by the Implementation
Requirements.
|
Followed. Executable code is generated in some cases, e.g. loops
to initialize large arrays.
C.5(8): Pragma Discard_Names
|
If the pragma applies to an entity, then the implementation should
reduce the amount of storage used for storing names associated with that
entity.
|
Followed.
C.7.2(30): The Package Task_Attributes
|
Some implementations are targeted to domains in which memory use at run
time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first N
attribute objects, and the heap for the others. In the latter case,
N should be documented.
|
Not followed. This implementation is not targeted to such a domain.
D.3(17): Locking Policies
|
The implementation should use names that end with _Locking for
locking policies defined by the implementation.
|
Followed. A single implementation-defined locking policy is defined,
whose name (Inheritance_Locking) follows this suggestion.
D.4(16): Entry Queuing Policies
|
Names that end with _Queuing should be used
for all implementation-defined queuing policies.
|
Followed. No such implementation-defined queuing policies exist.
D.6(9-10): Preemptive Abort
Even though the abort_statement is included in the list of
potentially blocking operations (see 9.5.1), it is recommended that this
statement be implemented in a way that never requires the task executing
the abort_statement to block.
|
Followed.
|
On a multi-processor, the delay associated with aborting a task on
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
|
Followed.
D.7(21): Tasking Restrictions
|
When feasible, the implementation should take advantage of the specified
restrictions to produce a more efficient implementation.
|
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
of restrictions are specified. See pragma Ravenscar and pragma
Restricted_Run_Time for more details.
D.8(47-49): Monotonic Time
When appropriate, implementations should provide configuration
mechanisms to change the value of Tick.
|
Such configuration mechanisms are not appropriate to this implementation
and are thus not supported.
It is recommended that Calendar.Clock and Real_Time.Clock
be implemented as transformations of the same time base.
|
Followed.
It is recommended that the best time base which exists in
the underlying system be available to the application through
Clock. Best may mean highest accuracy or largest range.
|
Followed.
E.5(28-29): Partition Communication Subsystem
|
Whenever possible, the PCS on the called partition should allow for
multiple tasks to call the RPC-receiver with different messages and
should allow them to block until the corresponding subprogram body
returns.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
The Write operation on a stream of type Params_Stream_Type
should raise Storage_Error if it runs out of space trying to
write the Item into the stream.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
F(7): COBOL Support
If COBOL (respectively, C) is widely supported in the target
environment, implementations supporting the Information Systems Annex
should provide the child package Interfaces.COBOL (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of COBOL (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
F.1(2): Decimal Radix Support
|
Packed decimal should be used as the internal representation for objects
of subtype S when S'Machine_Radix = 10.
|
Not followed. GNAT ignores S'Machine_Radix and always uses binary
representations.
G: Numerics
If Fortran (respectively, C) is widely supported in the target
environment, implementations supporting the Numerics Annex
should provide the child package Interfaces.Fortran (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of Fortran (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
G.1.1(56-58): Complex Types
|
Because the usual mathematical meaning of multiplication of a complex
operand and a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
|
Not followed.
Similarly, because the usual mathematical meaning of addition of a
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
complex addition. In implementations in which the Signed_Zeros
attribute of the component type is True (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
|
Not followed.
Implementations in which Real'Signed_Zeros is True should
attempt to provide a rational treatment of the signs of zero results and
result components. As one example, the result of the Argument
function should have the sign of the imaginary component of the
parameter X when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
of the Compose_From_Polar function should be the same as
(respectively, the opposite of) that of the Argument parameter when that
parameter has a value of zero and the Modulus parameter has a
nonnegative (respectively, negative) value.
|
Followed.
G.1.2(49): Complex Elementary Functions
Implementations in which Complex_Types.Real'Signed_Zeros is
True should attempt to provide a rational treatment of the signs
of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
a parameter component at the origin, or is always positive or always
negative.
|
Followed.
G.2.4(19): Accuracy Requirements
The versions of the forward trigonometric functions without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain. For the same reason, the
version of Log without a Base parameter should not be
implemented by calling the corresponding version with a Base
parameter of Numerics.e.
|
Followed.
G.2.6(15): Complex Arithmetic Accuracy
The version of the Compose_From_Polar function without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain.
|
Followed.
4 Implementation Defined Characteristics
In addition to the implementation dependent pragmas and attributes, and
the implementation advice, there are a number of other features of Ada
95 that are potentially implementation dependent. These are mentioned
throughout the Ada 95 Reference Manual, and are summarized in annex M.
A requirement for conforming Ada compilers is that they provide
documentation describing how the implementation deals with each of these
issues. In this chapter, you will find each point in annex M listed
followed by a description in italic font of how GNAT
handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation
dependent features in your programs if portability to other compilers
and other operating systems is an important consideration. The numbers
in each section below correspond to the paragraph number in the Ada 95
Reference Manual.
|
2. Whether or not each recommendation given in Implementation
Advice is followed. See 1.1.2(37).
|
See Implementation Advice.
|
3. Capacity limitations of the implementation. See 1.1.3(3).
|
The complexity of programs that can be processed is limited only by the
total amount of available virtual memory, and disk space for the
generated object files.
|
4. Variations from the standard that are impractical to avoid
given the implementation's execution environment. See 1.1.3(6).
|
There are no variations from the standard.
5. Which code_statements cause external
interactions. See 1.1.3(10).
|
Any code_statement can potentially cause external "cartouche" border="1">
If implementation-defined forms of interrupt handler procedures are
supported, such as protected procedures with parameters, then for each
such form of a handler, a type analogous to Parameterless_Handler
should be specified in a child package of Interrupts, with the
same operations as in the predefined package Interrupts.
|
Followed.
C.4(14): Pre-elaboration Requirements
|
It is recommended that pre-elaborated packages be implemented in such a
way that there should be little or no code executed at run time for the
elaboration of entities not already covered by the Implementation
Requirements.
|
Followed. Executable code is generated in some cases, e.g. loops
to initialize large arrays.
C.5(8): Pragma Discard_Names
|
If the pragma applies to an entity, then the implementation should
reduce the amount of storage used for storing names associated with that
entity.
|
Followed.
C.7.2(30): The Package Task_Attributes
|
Some implementations are targeted to domains in which memory use at run
time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first N
attribute objects, and the heap for the others. In the latter case,
N should be documented.
|
Not followed. This implementation is not targeted to such a domain.
D.3(17): Locking Policies
|
The implementation should use names that end with _Locking for
locking policies defined by the implementation.
|
Followed. A single implementation-defined locking policy is defined,
whose name (Inheritance_Locking) follows this suggestion.
D.4(16): Entry Queuing Policies
|
Names that end with _Queuing should be used
for all implementation-defined queuing policies.
|
Followed. No such implementation-defined queuing policies exist.
D.6(9-10): Preemptive Abort
Even though the abort_statement is included in the list of
potentially blocking operations (see 9.5.1), it is recommended that this
statement be implemented in a way that never requires the task executing
the abort_statement to block.
|
Followed.
|
On a multi-processor, the delay associated with aborting a task on
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
|
Followed.
D.7(21): Tasking Restrictions
|
When feasible, the implementation should take advantage of the specified
restrictions to produce a more efficient implementation.
|
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
of restrictions are specified. See pragma Ravenscar and pragma
Restricted_Run_Time for more details.
D.8(47-49): Monotonic Time
When appropriate, implementations should provide configuration
mechanisms to change the value of Tick.
|
Such configuration mechanisms are not appropriate to this implementation
and are thus not supported.
It is recommended that Calendar.Clock and Real_Time.Clock
be implemented as transformations of the same time base.
|
Followed.
It is recommended that the best time base which exists in
the underlying system be available to the application through
Clock. Best may mean highest accuracy or largest range.
|
Followed.
E.5(28-29): Partition Communication Subsystem
|
Whenever possible, the PCS on the called partition should allow for
multiple tasks to call the RPC-receiver with different messages and
should allow them to block until the corresponding subprogram body
returns.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
The Write operation on a stream of type Params_Stream_Type
should raise Storage_Error if it runs out of space trying to
write the Item into the stream.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
F(7): COBOL Support
If COBOL (respectively, C) is widely supported in the target
environment, implementations supporting the Information Systems Annex
should provide the child package Interfaces.COBOL (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of COBOL (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
F.1(2): Decimal Radix Support
|
Packed decimal should be used as the internal representation for objects
of subtype S when S'Machine_Radix = 10.
|
Not followed. GNAT ignores S'Machine_Radix and always uses binary
representations.
G: Numerics
If Fortran (respectively, C) is widely supported in the target
environment, implementations supporting the Numerics Annex
should provide the child package Interfaces.Fortran (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of Fortran (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
G.1.1(56-58): Complex Types
|
Because the usual mathematical meaning of multiplication of a complex
operand and a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
|
Not followed.
Similarly, because the usual mathematical meaning of addition of a
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
complex addition. In implementations in which the Signed_Zeros
attribute of the component type is True (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
|
Not followed.
Implementations in which Real'Signed_Zeros is True should
attempt to provide a rational treatment of the signs of zero results and
result components. As one example, the result of the Argument
function should have the sign of the imaginary component of the
parameter X when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
of the Compose_From_Polar function should be the same as
(respectively, the opposite of) that of the Argument parameter when that
parameter has a value of zero and the Modulus parameter has a
nonnegative (respectively, negative) value.
|
Followed.
G.1.2(49): Complex Elementary Functions
Implementations in which Complex_Types.Real'Signed_Zeros is
True should attempt to provide a rational treatment of the signs
of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
a parameter component at the origin, or is always positive or always
negative.
|
Followed.
G.2.4(19): Accuracy Requirements
The versions of the forward trigonometric functions without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain. For the same reason, the
version of Log without a Base parameter should not be
implemented by calling the corresponding version with a Base
parameter of Numerics.e.
|
Followed.
G.2.6(15): Complex Arithmetic Accuracy
The version of the Compose_From_Polar function without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain.
|
Followed.
4 Implementation Defined Characteristics
In addition to the implementation dependent pragmas and attributes, and
the implementation advice, there are a number of other features of Ada
95 that are potentially implementation dependent. These are mentioned
throughout the Ada 95 Reference Manual, and are summarized in annex M.
A requirement for conforming Ada compilers is that they provide
documentation describing how the implementation deals with each of these
issues. In this chapter, you will find each point in annex M listed
followed by a description in italic font of how GNAT
handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation
dependent features in your programs if portability to other compilers
and other operating systems is an important consideration. The numbers
in each section below correspond to the paragraph number in the Ada 95
Reference Manual.
|
2. Whether or not each recommendation given in Implementation
Advice is followed. See 1.1.2(37).
|
See Implementation Advice.
|
3. Capacity limitations of the implementation. See 1.1.3(3).
|
The complexity of programs that can be processed is limited only by the
total amount of available virtual memory, and disk space for the
generated object files.
|
4. Variations from the standard that are impractical to avoid
given the implementation's execution environment. See 1.1.3(6).
|
There are no variations from the standard.
5. Which code_statements cause external
interactions. See 1.1.3(10).
|
Any code_statement can potentially cause external "cartouche" border="1">
If implementation-defined forms of interrupt handler procedures are
supported, such as protected procedures with parameters, then for each
such form of a handler, a type analogous to Parameterless_Handler
should be specified in a child package of Interrupts, with the
same operations as in the predefined package Interrupts.
|
Followed.
C.4(14): Pre-elaboration Requirements
|
It is recommended that pre-elaborated packages be implemented in such a
way that there should be little or no code executed at run time for the
elaboration of entities not already covered by the Implementation
Requirements.
|
Followed. Executable code is generated in some cases, e.g. loops
to initialize large arrays.
C.5(8): Pragma Discard_Names
|
If the pragma applies to an entity, then the implementation should
reduce the amount of storage used for storing names associated with that
entity.
|
Followed.
C.7.2(30): The Package Task_Attributes
|
Some implementations are targeted to domains in which memory use at run
time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first N
attribute objects, and the heap for the others. In the latter case,
N should be documented.
|
Not followed. This implementation is not targeted to such a domain.
D.3(17): Locking Policies
|
The implementation should use names that end with _Locking for
locking policies defined by the implementation.
|
Followed. A single implementation-defined locking policy is defined,
whose name (Inheritance_Locking) follows this suggestion.
D.4(16): Entry Queuing Policies
|
Names that end with _Queuing should be used
for all implementation-defined queuing policies.
|
Followed. No such implementation-defined queuing policies exist.
D.6(9-10): Preemptive Abort
Even though the abort_statement is included in the list of
potentially blocking operations (see 9.5.1), it is recommended that this
statement be implemented in a way that never requires the task executing
the abort_statement to block.
|
Followed.
|
On a multi-processor, the delay associated with aborting a task on
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
|
Followed.
D.7(21): Tasking Restrictions
|
When feasible, the implementation should take advantage of the specified
restrictions to produce a more efficient implementation.
|
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
of restrictions are specified. See pragma Ravenscar and pragma
Restricted_Run_Time for more details.
D.8(47-49): Monotonic Time
When appropriate, implementations should provide configuration
mechanisms to change the value of Tick.
|
Such configuration mechanisms are not appropriate to this implementation
and are thus not supported.
It is recommended that Calendar.Clock and Real_Time.Clock
be implemented as transformations of the same time base.
|
Followed.
It is recommended that the best time base which exists in
the underlying system be available to the application through
Clock. Best may mean highest accuracy or largest range.
|
Followed.
E.5(28-29): Partition Communication Subsystem
|
Whenever possible, the PCS on the called partition should allow for
multiple tasks to call the RPC-receiver with different messages and
should allow them to block until the corresponding subprogram body
returns.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
The Write operation on a stream of type Params_Stream_Type
should raise Storage_Error if it runs out of space trying to
write the Item into the stream.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
F(7): COBOL Support
If COBOL (respectively, C) is widely supported in the target
environment, implementations supporting the Information Systems Annex
should provide the child package Interfaces.COBOL (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of COBOL (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
F.1(2): Decimal Radix Support
|
Packed decimal should be used as the internal representation for objects
of subtype S when S'Machine_Radix = 10.
|
Not followed. GNAT ignores S'Machine_Radix and always uses binary
representations.
G: Numerics
If Fortran (respectively, C) is widely supported in the target
environment, implementations supporting the Numerics Annex
should provide the child package Interfaces.Fortran (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of Fortran (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
G.1.1(56-58): Complex Types
|
Because the usual mathematical meaning of multiplication of a complex
operand and a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
|
Not followed.
Similarly, because the usual mathematical meaning of addition of a
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
complex addition. In implementations in which the Signed_Zeros
attribute of the component type is True (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
|
Not followed.
Implementations in which Real'Signed_Zeros is True should
attempt to provide a rational treatment of the signs of zero results and
result components. As one example, the result of the Argument
function should have the sign of the imaginary component of the
parameter X when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
of the Compose_From_Polar function should be the same as
(respectively, the opposite of) that of the Argument parameter when that
parameter has a value of zero and the Modulus parameter has a
nonnegative (respectively, negative) value.
|
Followed.
G.1.2(49): Complex Elementary Functions
Implementations in which Complex_Types.Real'Signed_Zeros is
True should attempt to provide a rational treatment of the signs
of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
a parameter component at the origin, or is always positive or always
negative.
|
Followed.
G.2.4(19): Accuracy Requirements
The versions of the forward trigonometric functions without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain. For the same reason, the
version of Log without a Base parameter should not be
implemented by calling the corresponding version with a Base
parameter of Numerics.e.
|
Followed.
G.2.6(15): Complex Arithmetic Accuracy
The version of the Compose_From_Polar function without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain.
|
Followed.
4 Implementation Defined Characteristics
In addition to the implementation dependent pragmas and attributes, and
the implementation advice, there are a number of other features of Ada
95 that are potentially implementation dependent. These are mentioned
throughout the Ada 95 Reference Manual, and are summarized in annex M.
A requirement for conforming Ada compilers is that they provide
documentation describing how the implementation deals with each of these
issues. In this chapter, you will find each point in annex M listed
followed by a description in italic font of how GNAT
handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation
dependent features in your programs if portability to other compilers
and other operating systems is an important consideration. The numbers
in each section below correspond to the paragraph number in the Ada 95
Reference Manual.
|
2. Whether or not each recommendation given in Implementation
Advice is followed. See 1.1.2(37).
|
See Implementation Advice.
|
3. Capacity limitations of the implementation. See 1.1.3(3).
|
The complexity of programs that can be processed is limited only by the
total amount of available virtual memory, and disk space for the
generated object files.
|
4. Variations from the standard that are impractical to avoid
given the implementation's execution environment. See 1.1.3(6).
|
There are no variations from the standard.
5. Which code_statements cause external
interactions. See 1.1.3(10).
|
Any code_statement can potentially cause external "cartouche" border="1">
If implementation-defined forms of interrupt handler procedures are
supported, such as protected procedures with parameters, then for each
such form of a handler, a type analogous to Parameterless_Handler
should be specified in a child package of Interrupts, with the
same operations as in the predefined package Interrupts.
|
Followed.
C.4(14): Pre-elaboration Requirements
|
It is recommended that pre-elaborated packages be implemented in such a
way that there should be little or no code executed at run time for the
elaboration of entities not already covered by the Implementation
Requirements.
|
Followed. Executable code is generated in some cases, e.g. loops
to initialize large arrays.
C.5(8): Pragma Discard_Names
|
If the pragma applies to an entity, then the implementation should
reduce the amount of storage used for storing names associated with that
entity.
|
Followed.
C.7.2(30): The Package Task_Attributes
|
Some implementations are targeted to domains in which memory use at run
time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first N
attribute objects, and the heap for the others. In the latter case,
N should be documented.
|
Not followed. This implementation is not targeted to such a domain.
D.3(17): Locking Policies
|
The implementation should use names that end with _Locking for
locking policies defined by the implementation.
|
Followed. A single implementation-defined locking policy is defined,
whose name (Inheritance_Locking) follows this suggestion.
D.4(16): Entry Queuing Policies
|
Names that end with _Queuing should be used
for all implementation-defined queuing policies.
|
Followed. No such implementation-defined queuing policies exist.
D.6(9-10): Preemptive Abort
Even though the abort_statement is included in the list of
potentially blocking operations (see 9.5.1), it is recommended that this
statement be implemented in a way that never requires the task executing
the abort_statement to block.
|
Followed.
|
On a multi-processor, the delay associated with aborting a task on
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
|
Followed.
D.7(21): Tasking Restrictions
|
When feasible, the implementation should take advantage of the specified
restrictions to produce a more efficient implementation.
|
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
of restrictions are specified. See pragma Ravenscar and pragma
Restricted_Run_Time for more details.
D.8(47-49): Monotonic Time
When appropriate, implementations should provide configuration
mechanisms to change the value of Tick.
|
Such configuration mechanisms are not appropriate to this implementation
and are thus not supported.
It is recommended that Calendar.Clock and Real_Time.Clock
be implemented as transformations of the same time base.
|
Followed.
It is recommended that the best time base which exists in
the underlying system be available to the application through
Clock. Best may mean highest accuracy or largest range.
|
Followed.
E.5(28-29): Partition Communication Subsystem
|
Whenever possible, the PCS on the called partition should allow for
multiple tasks to call the RPC-receiver with different messages and
should allow them to block until the corresponding subprogram body
returns.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
The Write operation on a stream of type Params_Stream_Type
should raise Storage_Error if it runs out of space trying to
write the Item into the stream.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
F(7): COBOL Support
If COBOL (respectively, C) is widely supported in the target
environment, implementations supporting the Information Systems Annex
should provide the child package Interfaces.COBOL (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of COBOL (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
F.1(2): Decimal Radix Support
|
Packed decimal should be used as the internal representation for objects
of subtype S when S'Machine_Radix = 10.
|
Not followed. GNAT ignores S'Machine_Radix and always uses binary
representations.
G: Numerics
If Fortran (respectively, C) is widely supported in the target
environment, implementations supporting the Numerics Annex
should provide the child package Interfaces.Fortran (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of Fortran (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
G.1.1(56-58): Complex Types
|
Because the usual mathematical meaning of multiplication of a complex
operand and a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
|
Not followed.
Similarly, because the usual mathematical meaning of addition of a
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
complex addition. In implementations in which the Signed_Zeros
attribute of the component type is True (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
|
Not followed.
Implementations in which Real'Signed_Zeros is True should
attempt to provide a rational treatment of the signs of zero results and
result components. As one example, the result of the Argument
function should have the sign of the imaginary component of the
parameter X when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
of the Compose_From_Polar function should be the same as
(respectively, the opposite of) that of the Argument parameter when that
parameter has a value of zero and the Modulus parameter has a
nonnegative (respectively, negative) value.
|
Followed.
G.1.2(49): Complex Elementary Functions
Implementations in which Complex_Types.Real'Signed_Zeros is
True should attempt to provide a rational treatment of the signs
of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
a parameter component at the origin, or is always positive or always
negative.
|
Followed.
G.2.4(19): Accuracy Requirements
The versions of the forward trigonometric functions without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain. For the same reason, the
version of Log without a Base parameter should not be
implemented by calling the corresponding version with a Base
parameter of Numerics.e.
|
Followed.
G.2.6(15): Complex Arithmetic Accuracy
The version of the Compose_From_Polar function without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain.
|
Followed.
4 Implementation Defined Characteristics
In addition to the implementation dependent pragmas and attributes, and
the implementation advice, there are a number of other features of Ada
95 that are potentially implementation dependent. These are mentioned
throughout the Ada 95 Reference Manual, and are summarized in annex M.
A requirement for conforming Ada compilers is that they provide
documentation describing how the implementation deals with each of these
issues. In this chapter, you will find each point in annex M listed
followed by a description in italic font of how GNAT
handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation
dependent features in your programs if portability to other compilers
and other operating systems is an important consideration. The numbers
in each section below correspond to the paragraph number in the Ada 95
Reference Manual.
|
2. Whether or not each recommendation given in Implementation
Advice is followed. See 1.1.2(37).
|
See Implementation Advice.
|
3. Capacity limitations of the implementation. See 1.1.3(3).
|
The complexity of programs that can be processed is limited only by the
total amount of available virtual memory, and disk space for the
generated object files.
|
4. Variations from the standard that are impractical to avoid
given the implementation's execution environment. See 1.1.3(6).
|
There are no variations from the standard.
5. Which code_statements cause external
interactions. See 1.1.3(10).
|
Any code_statement can potentially cause external "cartouche" border="1">
If implementation-defined forms of interrupt handler procedures are
supported, such as protected procedures with parameters, then for each
such form of a handler, a type analogous to Parameterless_Handler
should be specified in a child package of Interrupts, with the
same operations as in the predefined package Interrupts.
|
Followed.
C.4(14): Pre-elaboration Requirements
|
It is recommended that pre-elaborated packages be implemented in such a
way that there should be little or no code executed at run time for the
elaboration of entities not already covered by the Implementation
Requirements.
|
Followed. Executable code is generated in some cases, e.g. loops
to initialize large arrays.
C.5(8): Pragma Discard_Names
|
If the pragma applies to an entity, then the implementation should
reduce the amount of storage used for storing names associated with that
entity.
|
Followed.
C.7.2(30): The Package Task_Attributes
|
Some implementations are targeted to domains in which memory use at run
time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first N
attribute objects, and the heap for the others. In the latter case,
N should be documented.
|
Not followed. This implementation is not targeted to such a domain.
D.3(17): Locking Policies
|
The implementation should use names that end with _Locking for
locking policies defined by the implementation.
|
Followed. A single implementation-defined locking policy is defined,
whose name (Inheritance_Locking) follows this suggestion.
D.4(16): Entry Queuing Policies
|
Names that end with _Queuing should be used
for all implementation-defined queuing policies.
|
Followed. No such implementation-defined queuing policies exist.
D.6(9-10): Preemptive Abort
Even though the abort_statement is included in the list of
potentially blocking operations (see 9.5.1), it is recommended that this
statement be implemented in a way that never requires the task executing
the abort_statement to block.
|
Followed.
|
On a multi-processor, the delay associated with aborting a task on
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
|
Followed.
D.7(21): Tasking Restrictions
|
When feasible, the implementation should take advantage of the specified
restrictions to produce a more efficient implementation.
|
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
of restrictions are specified. See pragma Ravenscar and pragma
Restricted_Run_Time for more details.
D.8(47-49): Monotonic Time
When appropriate, implementations should provide configuration
mechanisms to change the value of Tick.
|
Such configuration mechanisms are not appropriate to this implementation
and are thus not supported.
It is recommended that Calendar.Clock and Real_Time.Clock
be implemented as transformations of the same time base.
|
Followed.
It is recommended that the best time base which exists in
the underlying system be available to the application through
Clock. Best may mean highest accuracy or largest range.
|
Followed.
E.5(28-29): Partition Communication Subsystem
|
Whenever possible, the PCS on the called partition should allow for
multiple tasks to call the RPC-receiver with different messages and
should allow them to block until the corresponding subprogram body
returns.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
The Write operation on a stream of type Params_Stream_Type
should raise Storage_Error if it runs out of space trying to
write the Item into the stream.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
F(7): COBOL Support
If COBOL (respectively, C) is widely supported in the target
environment, implementations supporting the Information Systems Annex
should provide the child package Interfaces.COBOL (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of COBOL (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
F.1(2): Decimal Radix Support
|
Packed decimal should be used as the internal representation for objects
of subtype S when S'Machine_Radix = 10.
|
Not followed. GNAT ignores S'Machine_Radix and always uses binary
representations.
G: Numerics
If Fortran (respectively, C) is widely supported in the target
environment, implementations supporting the Numerics Annex
should provide the child package Interfaces.Fortran (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of Fortran (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
G.1.1(56-58): Complex Types
|
Because the usual mathematical meaning of multiplication of a complex
operand and a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
|
Not followed.
Similarly, because the usual mathematical meaning of addition of a
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
complex addition. In implementations in which the Signed_Zeros
attribute of the component type is True (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
|
Not followed.
Implementations in which Real'Signed_Zeros is True should
attempt to provide a rational treatment of the signs of zero results and
result components. As one example, the result of the Argument
function should have the sign of the imaginary component of the
parameter X when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
of the Compose_From_Polar function should be the same as
(respectively, the opposite of) that of the Argument parameter when that
parameter has a value of zero and the Modulus parameter has a
nonnegative (respectively, negative) value.
|
Followed.
G.1.2(49): Complex Elementary Functions
Implementations in which Complex_Types.Real'Signed_Zeros is
True should attempt to provide a rational treatment of the signs
of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
a parameter component at the origin, or is always positive or always
negative.
|
Followed.
G.2.4(19): Accuracy Requirements
The versions of the forward trigonometric functions without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain. For the same reason, the
version of Log without a Base parameter should not be
implemented by calling the corresponding version with a Base
parameter of Numerics.e.
|
Followed.
G.2.6(15): Complex Arithmetic Accuracy
The version of the Compose_From_Polar function without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain.
|
Followed.
4 Implementation Defined Characteristics
In addition to the implementation dependent pragmas and attributes, and
the implementation advice, there are a number of other features of Ada
95 that are potentially implementation dependent. These are mentioned
throughout the Ada 95 Reference Manual, and are summarized in annex M.
A requirement for conforming Ada compilers is that they provide
documentation describing how the implementation deals with each of these
issues. In this chapter, you will find each point in annex M listed
followed by a description in italic font of how GNAT
handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation
dependent features in your programs if portability to other compilers
and other operating systems is an important consideration. The numbers
in each section below correspond to the paragraph number in the Ada 95
Reference Manual.
|
2. Whether or not each recommendation given in Implementation
Advice is followed. See 1.1.2(37).
|
See Implementation Advice.
|
3. Capacity limitations of the implementation. See 1.1.3(3).
|
The complexity of programs that can be processed is limited only by the
total amount of available virtual memory, and disk space for the
generated object files.
|
4. Variations from the standard that are impractical to avoid
given the implementation's execution environment. See 1.1.3(6).
|
There are no variations from the standard.
5. Which code_statements cause external
interactions. See 1.1.3(10).
|
Any code_statement can potentially cause external "cartouche" border="1">
If implementation-defined forms of interrupt handler procedures are
supported, such as protected procedures with parameters, then for each
such form of a handler, a type analogous to Parameterless_Handler
should be specified in a child package of Interrupts, with the
same operations as in the predefined package Interrupts.
|
Followed.
C.4(14): Pre-elaboration Requirements
|
It is recommended that pre-elaborated packages be implemented in such a
way that there should be little or no code executed at run time for the
elaboration of entities not already covered by the Implementation
Requirements.
|
Followed. Executable code is generated in some cases, e.g. loops
to initialize large arrays.
C.5(8): Pragma Discard_Names
|
If the pragma applies to an entity, then the implementation should
reduce the amount of storage used for storing names associated with that
entity.
|
Followed.
C.7.2(30): The Package Task_Attributes
|
Some implementations are targeted to domains in which memory use at run
time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first N
attribute objects, and the heap for the others. In the latter case,
N should be documented.
|
Not followed. This implementation is not targeted to such a domain.
D.3(17): Locking Policies
|
The implementation should use names that end with _Locking for
locking policies defined by the implementation.
|
Followed. A single implementation-defined locking policy is defined,
whose name (Inheritance_Locking) follows this suggestion.
D.4(16): Entry Queuing Policies
|
Names that end with _Queuing should be used
for all implementation-defined queuing policies.
|
Followed. No such implementation-defined queuing policies exist.
D.6(9-10): Preemptive Abort
Even though the abort_statement is included in the list of
potentially blocking operations (see 9.5.1), it is recommended that this
statement be implemented in a way that never requires the task executing
the abort_statement to block.
|
Followed.
|
On a multi-processor, the delay associated with aborting a task on
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
|
Followed.
D.7(21): Tasking Restrictions
|
When feasible, the implementation should take advantage of the specified
restrictions to produce a more efficient implementation.
|
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
of restrictions are specified. See pragma Ravenscar and pragma
Restricted_Run_Time for more details.
D.8(47-49): Monotonic Time
When appropriate, implementations should provide configuration
mechanisms to change the value of Tick.
|
Such configuration mechanisms are not appropriate to this implementation
and are thus not supported.
It is recommended that Calendar.Clock and Real_Time.Clock
be implemented as transformations of the same time base.
|
Followed.
It is recommended that the best time base which exists in
the underlying system be available to the application through
Clock. Best may mean highest accuracy or largest range.
|
Followed.
E.5(28-29): Partition Communication Subsystem
|
Whenever possible, the PCS on the called partition should allow for
multiple tasks to call the RPC-receiver with different messages and
should allow them to block until the corresponding subprogram body
returns.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
The Write operation on a stream of type Params_Stream_Type
should raise Storage_Error if it runs out of space trying to
write the Item into the stream.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
F(7): COBOL Support
If COBOL (respectively, C) is widely supported in the target
environment, implementations supporting the Information Systems Annex
should provide the child package Interfaces.COBOL (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of COBOL (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
F.1(2): Decimal Radix Support
|
Packed decimal should be used as the internal representation for objects
of subtype S when S'Machine_Radix = 10.
|
Not followed. GNAT ignores S'Machine_Radix and always uses binary
representations.
G: Numerics
If Fortran (respectively, C) is widely supported in the target
environment, implementations supporting the Numerics Annex
should provide the child package Interfaces.Fortran (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of Fortran (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
G.1.1(56-58): Complex Types
|
Because the usual mathematical meaning of multiplication of a complex
operand and a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
|
Not followed.
Similarly, because the usual mathematical meaning of addition of a
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
complex addition. In implementations in which the Signed_Zeros
attribute of the component type is True (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
|
Not followed.
Implementations in which Real'Signed_Zeros is True should
attempt to provide a rational treatment of the signs of zero results and
result components. As one example, the result of the Argument
function should have the sign of the imaginary component of the
parameter X when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
of the Compose_From_Polar function should be the same as
(respectively, the opposite of) that of the Argument parameter when that
parameter has a value of zero and the Modulus parameter has a
nonnegative (respectively, negative) value.
|
Followed.
G.1.2(49): Complex Elementary Functions
Implementations in which Complex_Types.Real'Signed_Zeros is
True should attempt to provide a rational treatment of the signs
of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
a parameter component at the origin, or is always positive or always
negative.
|
Followed.
G.2.4(19): Accuracy Requirements
The versions of the forward trigonometric functions without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain. For the same reason, the
version of Log without a Base parameter should not be
implemented by calling the corresponding version with a Base
parameter of Numerics.e.
|
Followed.
G.2.6(15): Complex Arithmetic Accuracy
The version of the Compose_From_Polar function without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain.
|
Followed.
4 Implementation Defined Characteristics
In addition to the implementation dependent pragmas and attributes, and
the implementation advice, there are a number of other features of Ada
95 that are potentially implementation dependent. These are mentioned
throughout the Ada 95 Reference Manual, and are summarized in annex M.
A requirement for conforming Ada compilers is that they provide
documentation describing how the implementation deals with each of these
issues. In this chapter, you will find each point in annex M listed
followed by a description in italic font of how GNAT
handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation
dependent features in your programs if portability to other compilers
and other operating systems is an important consideration. The numbers
in each section below correspond to the paragraph number in the Ada 95
Reference Manual.
|
2. Whether or not each recommendation given in Implementation
Advice is followed. See 1.1.2(37).
|
See Implementation Advice.
|
3. Capacity limitations of the implementation. See 1.1.3(3).
|
The complexity of programs that can be processed is limited only by the
total amount of available virtual memory, and disk space for the
generated object files.
|
4. Variations from the standard that are impractical to avoid
given the implementation's execution environment. See 1.1.3(6).
|
There are no variations from the standard.
5. Which code_statements cause external
interactions. See 1.1.3(10).
|
Any code_statement can potentially cause external "cartouche" border="1">
If implementation-defined forms of interrupt handler procedures are
supported, such as protected procedures with parameters, then for each
such form of a handler, a type analogous to Parameterless_Handler
should be specified in a child package of Interrupts, with the
same operations as in the predefined package Interrupts.
|
Followed.
C.4(14): Pre-elaboration Requirements
|
It is recommended that pre-elaborated packages be implemented in such a
way that there should be little or no code executed at run time for the
elaboration of entities not already covered by the Implementation
Requirements.
|
Followed. Executable code is generated in some cases, e.g. loops
to initialize large arrays.
C.5(8): Pragma Discard_Names
|
If the pragma applies to an entity, then the implementation should
reduce the amount of storage used for storing names associated with that
entity.
|
Followed.
C.7.2(30): The Package Task_Attributes
|
Some implementations are targeted to domains in which memory use at run
time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first N
attribute objects, and the heap for the others. In the latter case,
N should be documented.
|
Not followed. This implementation is not targeted to such a domain.
D.3(17): Locking Policies
|
The implementation should use names that end with _Locking for
locking policies defined by the implementation.
|
Followed. A single implementation-defined locking policy is defined,
whose name (Inheritance_Locking) follows this suggestion.
D.4(16): Entry Queuing Policies
|
Names that end with _Queuing should be used
for all implementation-defined queuing policies.
|
Followed. No such implementation-defined queuing policies exist.
D.6(9-10): Preemptive Abort
Even though the abort_statement is included in the list of
potentially blocking operations (see 9.5.1), it is recommended that this
statement be implemented in a way that never requires the task executing
the abort_statement to block.
|
Followed.
|
On a multi-processor, the delay associated with aborting a task on
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
|
Followed.
D.7(21): Tasking Restrictions
|
When feasible, the implementation should take advantage of the specified
restrictions to produce a more efficient implementation.
|
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
of restrictions are specified. See pragma Ravenscar and pragma
Restricted_Run_Time for more details.
D.8(47-49): Monotonic Time
When appropriate, implementations should provide configuration
mechanisms to change the value of Tick.
|
Such configuration mechanisms are not appropriate to this implementation
and are thus not supported.
It is recommended that Calendar.Clock and Real_Time.Clock
be implemented as transformations of the same time base.
|
Followed.
It is recommended that the best time base which exists in
the underlying system be available to the application through
Clock. Best may mean highest accuracy or largest range.
|
Followed.
E.5(28-29): Partition Communication Subsystem
|
Whenever possible, the PCS on the called partition should allow for
multiple tasks to call the RPC-receiver with different messages and
should allow them to block until the corresponding subprogram body
returns.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
The Write operation on a stream of type Params_Stream_Type
should raise Storage_Error if it runs out of space trying to
write the Item into the stream.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
F(7): COBOL Support
If COBOL (respectively, C) is widely supported in the target
environment, implementations supporting the Information Systems Annex
should provide the child package Interfaces.COBOL (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of COBOL (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
F.1(2): Decimal Radix Support
|
Packed decimal should be used as the internal representation for objects
of subtype S when S'Machine_Radix = 10.
|
Not followed. GNAT ignores S'Machine_Radix and always uses binary
representations.
G: Numerics
If Fortran (respectively, C) is widely supported in the target
environment, implementations supporting the Numerics Annex
should provide the child package Interfaces.Fortran (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of Fortran (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
G.1.1(56-58): Complex Types
|
Because the usual mathematical meaning of multiplication of a complex
operand and a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
|
Not followed.
Similarly, because the usual mathematical meaning of addition of a
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
complex addition. In implementations in which the Signed_Zeros
attribute of the component type is True (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
|
Not followed.
Implementations in which Real'Signed_Zeros is True should
attempt to provide a rational treatment of the signs of zero results and
result components. As one example, the result of the Argument
function should have the sign of the imaginary component of the
parameter X when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
of the Compose_From_Polar function should be the same as
(respectively, the opposite of) that of the Argument parameter when that
parameter has a value of zero and the Modulus parameter has a
nonnegative (respectively, negative) value.
|
Followed.
G.1.2(49): Complex Elementary Functions
Implementations in which Complex_Types.Real'Signed_Zeros is
True should attempt to provide a rational treatment of the signs
of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
a parameter component at the origin, or is always positive or always
negative.
|
Followed.
G.2.4(19): Accuracy Requirements
The versions of the forward trigonometric functions without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain. For the same reason, the
version of Log without a Base parameter should not be
implemented by calling the corresponding version with a Base
parameter of Numerics.e.
|
Followed.
G.2.6(15): Complex Arithmetic Accuracy
The version of the Compose_From_Polar function without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain.
|
Followed.
4 Implementation Defined Characteristics
In addition to the implementation dependent pragmas and attributes, and
the implementation advice, there are a number of other features of Ada
95 that are potentially implementation dependent. These are mentioned
throughout the Ada 95 Reference Manual, and are summarized in annex M.
A requirement for conforming Ada compilers is that they provide
documentation describing how the implementation deals with each of these
issues. In this chapter, you will find each point in annex M listed
followed by a description in italic font of how GNAT
handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation
dependent features in your programs if portability to other compilers
and other operating systems is an important consideration. The numbers
in each section below correspond to the paragraph number in the Ada 95
Reference Manual.
|
2. Whether or not each recommendation given in Implementation
Advice is followed. See 1.1.2(37).
|
See Implementation Advice.
|
3. Capacity limitations of the implementation. See 1.1.3(3).
|
The complexity of programs that can be processed is limited only by the
total amount of available virtual memory, and disk space for the
generated object files.
|
4. Variations from the standard that are impractical to avoid
given the implementation's execution environment. See 1.1.3(6).
|
There are no variations from the standard.
5. Which code_statements cause external
interactions. See 1.1.3(10).
|
Any code_statement can potentially cause external "cartouche" border="1">
If implementation-defined forms of interrupt handler procedures are
supported, such as protected procedures with parameters, then for each
such form of a handler, a type analogous to Parameterless_Handler
should be specified in a child package of Interrupts, with the
same operations as in the predefined package Interrupts.
|
Followed.
C.4(14): Pre-elaboration Requirements
|
It is recommended that pre-elaborated packages be implemented in such a
way that there should be little or no code executed at run time for the
elaboration of entities not already covered by the Implementation
Requirements.
|
Followed. Executable code is generated in some cases, e.g. loops
to initialize large arrays.
C.5(8): Pragma Discard_Names
|
If the pragma applies to an entity, then the implementation should
reduce the amount of storage used for storing names associated with that
entity.
|
Followed.
C.7.2(30): The Package Task_Attributes
|
Some implementations are targeted to domains in which memory use at run
time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first N
attribute objects, and the heap for the others. In the latter case,
N should be documented.
|
Not followed. This implementation is not targeted to such a domain.
D.3(17): Locking Policies
|
The implementation should use names that end with _Locking for
locking policies defined by the implementation.
|
Followed. A single implementation-defined locking policy is defined,
whose name (Inheritance_Locking) follows this suggestion.
D.4(16): Entry Queuing Policies
|
Names that end with _Queuing should be used
for all implementation-defined queuing policies.
|
Followed. No such implementation-defined queuing policies exist.
D.6(9-10): Preemptive Abort
Even though the abort_statement is included in the list of
potentially blocking operations (see 9.5.1), it is recommended that this
statement be implemented in a way that never requires the task executing
the abort_statement to block.
|
Followed.
|
On a multi-processor, the delay associated with aborting a task on
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
|
Followed.
D.7(21): Tasking Restrictions
|
When feasible, the implementation should take advantage of the specified
restrictions to produce a more efficient implementation.
|
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
of restrictions are specified. See pragma Ravenscar and pragma
Restricted_Run_Time for more details.
D.8(47-49): Monotonic Time
When appropriate, implementations should provide configuration
mechanisms to change the value of Tick.
|
Such configuration mechanisms are not appropriate to this implementation
and are thus not supported.
It is recommended that Calendar.Clock and Real_Time.Clock
be implemented as transformations of the same time base.
|
Followed.
It is recommended that the best time base which exists in
the underlying system be available to the application through
Clock. Best may mean highest accuracy or largest range.
|
Followed.
E.5(28-29): Partition Communication Subsystem
|
Whenever possible, the PCS on the called partition should allow for
multiple tasks to call the RPC-receiver with different messages and
should allow them to block until the corresponding subprogram body
returns.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
The Write operation on a stream of type Params_Stream_Type
should raise Storage_Error if it runs out of space trying to
write the Item into the stream.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
F(7): COBOL Support
If COBOL (respectively, C) is widely supported in the target
environment, implementations supporting the Information Systems Annex
should provide the child package Interfaces.COBOL (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of COBOL (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
F.1(2): Decimal Radix Support
|
Packed decimal should be used as the internal representation for objects
of subtype S when S'Machine_Radix = 10.
|
Not followed. GNAT ignores S'Machine_Radix and always uses binary
representations.
G: Numerics
If Fortran (respectively, C) is widely supported in the target
environment, implementations supporting the Numerics Annex
should provide the child package Interfaces.Fortran (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of Fortran (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
G.1.1(56-58): Complex Types
|
Because the usual mathematical meaning of multiplication of a complex
operand and a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
|
Not followed.
Similarly, because the usual mathematical meaning of addition of a
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
complex addition. In implementations in which the Signed_Zeros
attribute of the component type is True (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
|
Not followed.
Implementations in which Real'Signed_Zeros is True should
attempt to provide a rational treatment of the signs of zero results and
result components. As one example, the result of the Argument
function should have the sign of the imaginary component of the
parameter X when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
of the Compose_From_Polar function should be the same as
(respectively, the opposite of) that of the Argument parameter when that
parameter has a value of zero and the Modulus parameter has a
nonnegative (respectively, negative) value.
|
Followed.
G.1.2(49): Complex Elementary Functions
Implementations in which Complex_Types.Real'Signed_Zeros is
True should attempt to provide a rational treatment of the signs
of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
a parameter component at the origin, or is always positive or always
negative.
|
Followed.
G.2.4(19): Accuracy Requirements
The versions of the forward trigonometric functions without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain. For the same reason, the
version of Log without a Base parameter should not be
implemented by calling the corresponding version with a Base
parameter of Numerics.e.
|
Followed.
G.2.6(15): Complex Arithmetic Accuracy
The version of the Compose_From_Polar function without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain.
|
Followed.
4 Implementation Defined Characteristics
In addition to the implementation dependent pragmas and attributes, and
the implementation advice, there are a number of other features of Ada
95 that are potentially implementation dependent. These are mentioned
throughout the Ada 95 Reference Manual, and are summarized in annex M.
A requirement for conforming Ada compilers is that they provide
documentation describing how the implementation deals with each of these
issues. In this chapter, you will find each point in annex M listed
followed by a description in italic font of how GNAT
handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation
dependent features in your programs if portability to other compilers
and other operating systems is an important consideration. The numbers
in each section below correspond to the paragraph number in the Ada 95
Reference Manual.
|
2. Whether or not each recommendation given in Implementation
Advice is followed. See 1.1.2(37).
|
See Implementation Advice.
|
3. Capacity limitations of the implementation. See 1.1.3(3).
|
The complexity of programs that can be processed is limited only by the
total amount of available virtual memory, and disk space for the
generated object files.
|
4. Variations from the standard that are impractical to avoid
given the implementation's execution environment. See 1.1.3(6).
|
There are no variations from the standard.
5. Which code_statements cause external
interactions. See 1.1.3(10).
|
Any code_statement can potentially cause external "cartouche" border="1">
If implementation-defined forms of interrupt handler procedures are
supported, such as protected procedures with parameters, then for each
such form of a handler, a type analogous to Parameterless_Handler
should be specified in a child package of Interrupts, with the
same operations as in the predefined package Interrupts.
|
Followed.
C.4(14): Pre-elaboration Requirements
|
It is recommended that pre-elaborated packages be implemented in such a
way that there should be little or no code executed at run time for the
elaboration of entities not already covered by the Implementation
Requirements.
|
Followed. Executable code is generated in some cases, e.g. loops
to initialize large arrays.
C.5(8): Pragma Discard_Names
|
If the pragma applies to an entity, then the implementation should
reduce the amount of storage used for storing names associated with that
entity.
|
Followed.
C.7.2(30): The Package Task_Attributes
|
Some implementations are targeted to domains in which memory use at run
time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first N
attribute objects, and the heap for the others. In the latter case,
N should be documented.
|
Not followed. This implementation is not targeted to such a domain.
D.3(17): Locking Policies
|
The implementation should use names that end with _Locking for
locking policies defined by the implementation.
|
Followed. A single implementation-defined locking policy is defined,
whose name (Inheritance_Locking) follows this suggestion.
D.4(16): Entry Queuing Policies
|
Names that end with _Queuing should be used
for all implementation-defined queuing policies.
|
Followed. No such implementation-defined queuing policies exist.
D.6(9-10): Preemptive Abort
Even though the abort_statement is included in the list of
potentially blocking operations (see 9.5.1), it is recommended that this
statement be implemented in a way that never requires the task executing
the abort_statement to block.
|
Followed.
|
On a multi-processor, the delay associated with aborting a task on
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
|
Followed.
D.7(21): Tasking Restrictions
|
When feasible, the implementation should take advantage of the specified
restrictions to produce a more efficient implementation.
|
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
of restrictions are specified. See pragma Ravenscar and pragma
Restricted_Run_Time for more details.
D.8(47-49): Monotonic Time
When appropriate, implementations should provide configuration
mechanisms to change the value of Tick.
|
Such configuration mechanisms are not appropriate to this implementation
and are thus not supported.
It is recommended that Calendar.Clock and Real_Time.Clock
be implemented as transformations of the same time base.
|
Followed.
It is recommended that the best time base which exists in
the underlying system be available to the application through
Clock. Best may mean highest accuracy or largest range.
|
Followed.
E.5(28-29): Partition Communication Subsystem
|
Whenever possible, the PCS on the called partition should allow for
multiple tasks to call the RPC-receiver with different messages and
should allow them to block until the corresponding subprogram body
returns.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
The Write operation on a stream of type Params_Stream_Type
should raise Storage_Error if it runs out of space trying to
write the Item into the stream.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
F(7): COBOL Support
If COBOL (respectively, C) is widely supported in the target
environment, implementations supporting the Information Systems Annex
should provide the child package Interfaces.COBOL (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of COBOL (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
F.1(2): Decimal Radix Support
|
Packed decimal should be used as the internal representation for objects
of subtype S when S'Machine_Radix = 10.
|
Not followed. GNAT ignores S'Machine_Radix and always uses binary
representations.
G: Numerics
If Fortran (respectively, C) is widely supported in the target
environment, implementations supporting the Numerics Annex
should provide the child package Interfaces.Fortran (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of Fortran (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
G.1.1(56-58): Complex Types
|
Because the usual mathematical meaning of multiplication of a complex
operand and a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
|
Not followed.
Similarly, because the usual mathematical meaning of addition of a
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
complex addition. In implementations in which the Signed_Zeros
attribute of the component type is True (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
|
Not followed.
Implementations in which Real'Signed_Zeros is True should
attempt to provide a rational treatment of the signs of zero results and
result components. As one example, the result of the Argument
function should have the sign of the imaginary component of the
parameter X when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
of the Compose_From_Polar function should be the same as
(respectively, the opposite of) that of the Argument parameter when that
parameter has a value of zero and the Modulus parameter has a
nonnegative (respectively, negative) value.
|
Followed.
G.1.2(49): Complex Elementary Functions
Implementations in which Complex_Types.Real'Signed_Zeros is
True should attempt to provide a rational treatment of the signs
of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
a parameter component at the origin, or is always positive or always
negative.
|
Followed.
G.2.4(19): Accuracy Requirements
The versions of the forward trigonometric functions without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain. For the same reason, the
version of Log without a Base parameter should not be
implemented by calling the corresponding version with a Base
parameter of Numerics.e.
|
Followed.
G.2.6(15): Complex Arithmetic Accuracy
The version of the Compose_From_Polar function without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain.
|
Followed.
4 Implementation Defined Characteristics
In addition to the implementation dependent pragmas and attributes, and
the implementation advice, there are a number of other features of Ada
95 that are potentially implementation dependent. These are mentioned
throughout the Ada 95 Reference Manual, and are summarized in annex M.
A requirement for conforming Ada compilers is that they provide
documentation describing how the implementation deals with each of these
issues. In this chapter, you will find each point in annex M listed
followed by a description in italic font of how GNAT
handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation
dependent features in your programs if portability to other compilers
and other operating systems is an important consideration. The numbers
in each section below correspond to the paragraph number in the Ada 95
Reference Manual.
|
2. Whether or not each recommendation given in Implementation
Advice is followed. See 1.1.2(37).
|
See Implementation Advice.
|
3. Capacity limitations of the implementation. See 1.1.3(3).
|
The complexity of programs that can be processed is limited only by the
total amount of available virtual memory, and disk space for the
generated object files.
|
4. Variations from the standard that are impractical to avoid
given the implementation's execution environment. See 1.1.3(6).
|
There are no variations from the standard.
5. Which code_statements cause external
interactions. See 1.1.3(10).
|
Any code_statement can potentially cause external "cartouche" border="1">
If implementation-defined forms of interrupt handler procedures are
supported, such as protected procedures with parameters, then for each
such form of a handler, a type analogous to Parameterless_Handler
should be specified in a child package of Interrupts, with the
same operations as in the predefined package Interrupts.
|
Followed.
C.4(14): Pre-elaboration Requirements
|
It is recommended that pre-elaborated packages be implemented in such a
way that there should be little or no code executed at run time for the
elaboration of entities not already covered by the Implementation
Requirements.
|
Followed. Executable code is generated in some cases, e.g. loops
to initialize large arrays.
C.5(8): Pragma Discard_Names
|
If the pragma applies to an entity, then the implementation should
reduce the amount of storage used for storing names associated with that
entity.
|
Followed.
C.7.2(30): The Package Task_Attributes
|
Some implementations are targeted to domains in which memory use at run
time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first N
attribute objects, and the heap for the others. In the latter case,
N should be documented.
|
Not followed. This implementation is not targeted to such a domain.
D.3(17): Locking Policies
|
The implementation should use names that end with _Locking for
locking policies defined by the implementation.
|
Followed. A single implementation-defined locking policy is defined,
whose name (Inheritance_Locking) follows this suggestion.
D.4(16): Entry Queuing Policies
|
Names that end with _Queuing should be used
for all implementation-defined queuing policies.
|
Followed. No such implementation-defined queuing policies exist.
D.6(9-10): Preemptive Abort
Even though the abort_statement is included in the list of
potentially blocking operations (see 9.5.1), it is recommended that this
statement be implemented in a way that never requires the task executing
the abort_statement to block.
|
Followed.
|
On a multi-processor, the delay associated with aborting a task on
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
|
Followed.
D.7(21): Tasking Restrictions
|
When feasible, the implementation should take advantage of the specified
restrictions to produce a more efficient implementation.
|
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
of restrictions are specified. See pragma Ravenscar and pragma
Restricted_Run_Time for more details.
D.8(47-49): Monotonic Time
When appropriate, implementations should provide configuration
mechanisms to change the value of Tick.
|
Such configuration mechanisms are not appropriate to this implementation
and are thus not supported.
It is recommended that Calendar.Clock and Real_Time.Clock
be implemented as transformations of the same time base.
|
Followed.
It is recommended that the best time base which exists in
the underlying system be available to the application through
Clock. Best may mean highest accuracy or largest range.
|
Followed.
E.5(28-29): Partition Communication Subsystem
|
Whenever possible, the PCS on the called partition should allow for
multiple tasks to call the RPC-receiver with different messages and
should allow them to block until the corresponding subprogram body
returns.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
The Write operation on a stream of type Params_Stream_Type
should raise Storage_Error if it runs out of space trying to
write the Item into the stream.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
F(7): COBOL Support
If COBOL (respectively, C) is widely supported in the target
environment, implementations supporting the Information Systems Annex
should provide the child package Interfaces.COBOL (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of COBOL (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
F.1(2): Decimal Radix Support
|
Packed decimal should be used as the internal representation for objects
of subtype S when S'Machine_Radix = 10.
|
Not followed. GNAT ignores S'Machine_Radix and always uses binary
representations.
G: Numerics
If Fortran (respectively, C) is widely supported in the target
environment, implementations supporting the Numerics Annex
should provide the child package Interfaces.Fortran (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of Fortran (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
G.1.1(56-58): Complex Types
|
Because the usual mathematical meaning of multiplication of a complex
operand and a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
|
Not followed.
Similarly, because the usual mathematical meaning of addition of a
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
complex addition. In implementations in which the Signed_Zeros
attribute of the component type is True (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
|
Not followed.
Implementations in which Real'Signed_Zeros is True should
attempt to provide a rational treatment of the signs of zero results and
result components. As one example, the result of the Argument
function should have the sign of the imaginary component of the
parameter X when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
of the Compose_From_Polar function should be the same as
(respectively, the opposite of) that of the Argument parameter when that
parameter has a value of zero and the Modulus parameter has a
nonnegative (respectively, negative) value.
|
Followed.
G.1.2(49): Complex Elementary Functions
Implementations in which Complex_Types.Real'Signed_Zeros is
True should attempt to provide a rational treatment of the signs
of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
a parameter component at the origin, or is always positive or always
negative.
|
Followed.
G.2.4(19): Accuracy Requirements
The versions of the forward trigonometric functions without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain. For the same reason, the
version of Log without a Base parameter should not be
implemented by calling the corresponding version with a Base
parameter of Numerics.e.
|
Followed.
G.2.6(15): Complex Arithmetic Accuracy
The version of the Compose_From_Polar function without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain.
|
Followed.
4 Implementation Defined Characteristics
In addition to the implementation dependent pragmas and attributes, and
the implementation advice, there are a number of other features of Ada
95 that are potentially implementation dependent. These are mentioned
throughout the Ada 95 Reference Manual, and are summarized in annex M.
A requirement for conforming Ada compilers is that they provide
documentation describing how the implementation deals with each of these
issues. In this chapter, you will find each point in annex M listed
followed by a description in italic font of how GNAT
handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation
dependent features in your programs if portability to other compilers
and other operating systems is an important consideration. The numbers
in each section below correspond to the paragraph number in the Ada 95
Reference Manual.
|
2. Whether or not each recommendation given in Implementation
Advice is followed. See 1.1.2(37).
|
See Implementation Advice.
|
3. Capacity limitations of the implementation. See 1.1.3(3).
|
The complexity of programs that can be processed is limited only by the
total amount of available virtual memory, and disk space for the
generated object files.
|
4. Variations from the standard that are impractical to avoid
given the implementation's execution environment. See 1.1.3(6).
|
There are no variations from the standard.
5. Which code_statements cause external
interactions. See 1.1.3(10).
|
Any code_statement can potentially cause external "cartouche" border="1">
If implementation-defined forms of interrupt handler procedures are
supported, such as protected procedures with parameters, then for each
such form of a handler, a type analogous to Parameterless_Handler
should be specified in a child package of Interrupts, with the
same operations as in the predefined package Interrupts.
|
Followed.
C.4(14): Pre-elaboration Requirements
|
It is recommended that pre-elaborated packages be implemented in such a
way that there should be little or no code executed at run time for the
elaboration of entities not already covered by the Implementation
Requirements.
|
Followed. Executable code is generated in some cases, e.g. loops
to initialize large arrays.
C.5(8): Pragma Discard_Names
|
If the pragma applies to an entity, then the implementation should
reduce the amount of storage used for storing names associated with that
entity.
|
Followed.
C.7.2(30): The Package Task_Attributes
|
Some implementations are targeted to domains in which memory use at run
time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first N
attribute objects, and the heap for the others. In the latter case,
N should be documented.
|
Not followed. This implementation is not targeted to such a domain.
D.3(17): Locking Policies
|
The implementation should use names that end with _Locking for
locking policies defined by the implementation.
|
Followed. A single implementation-defined locking policy is defined,
whose name (Inheritance_Locking) follows this suggestion.
D.4(16): Entry Queuing Policies
|
Names that end with _Queuing should be used
for all implementation-defined queuing policies.
|
Followed. No such implementation-defined queuing policies exist.
D.6(9-10): Preemptive Abort
Even though the abort_statement is included in the list of
potentially blocking operations (see 9.5.1), it is recommended that this
statement be implemented in a way that never requires the task executing
the abort_statement to block.
|
Followed.
|
On a multi-processor, the delay associated with aborting a task on
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
|
Followed.
D.7(21): Tasking Restrictions
|
When feasible, the implementation should take advantage of the specified
restrictions to produce a more efficient implementation.
|
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
of restrictions are specified. See pragma Ravenscar and pragma
Restricted_Run_Time for more details.
D.8(47-49): Monotonic Time
When appropriate, implementations should provide configuration
mechanisms to change the value of Tick.
|
Such configuration mechanisms are not appropriate to this implementation
and are thus not supported.
It is recommended that Calendar.Clock and Real_Time.Clock
be implemented as transformations of the same time base.
|
Followed.
It is recommended that the best time base which exists in
the underlying system be available to the application through
Clock. Best may mean highest accuracy or largest range.
|
Followed.
E.5(28-29): Partition Communication Subsystem
|
Whenever possible, the PCS on the called partition should allow for
multiple tasks to call the RPC-receiver with different messages and
should allow them to block until the corresponding subprogram body
returns.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
The Write operation on a stream of type Params_Stream_Type
should raise Storage_Error if it runs out of space trying to
write the Item into the stream.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
F(7): COBOL Support
If COBOL (respectively, C) is widely supported in the target
environment, implementations supporting the Information Systems Annex
should provide the child package Interfaces.COBOL (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of COBOL (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
F.1(2): Decimal Radix Support
|
Packed decimal should be used as the internal representation for objects
of subtype S when S'Machine_Radix = 10.
|
Not followed. GNAT ignores S'Machine_Radix and always uses binary
representations.
G: Numerics
If Fortran (respectively, C) is widely supported in the target
environment, implementations supporting the Numerics Annex
should provide the child package Interfaces.Fortran (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of Fortran (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
G.1.1(56-58): Complex Types
|
Because the usual mathematical meaning of multiplication of a complex
operand and a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
|
Not followed.
Similarly, because the usual mathematical meaning of addition of a
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
complex addition. In implementations in which the Signed_Zeros
attribute of the component type is True (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
|
Not followed.
Implementations in which Real'Signed_Zeros is True should
attempt to provide a rational treatment of the signs of zero results and
result components. As one example, the result of the Argument
function should have the sign of the imaginary component of the
parameter X when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
of the Compose_From_Polar function should be the same as
(respectively, the opposite of) that of the Argument parameter when that
parameter has a value of zero and the Modulus parameter has a
nonnegative (respectively, negative) value.
|
Followed.
G.1.2(49): Complex Elementary Functions
Implementations in which Complex_Types.Real'Signed_Zeros is
True should attempt to provide a rational treatment of the signs
of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
a parameter component at the origin, or is always positive or always
negative.
|
Followed.
G.2.4(19): Accuracy Requirements
The versions of the forward trigonometric functions without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain. For the same reason, the
version of Log without a Base parameter should not be
implemented by calling the corresponding version with a Base
parameter of Numerics.e.
|
Followed.
G.2.6(15): Complex Arithmetic Accuracy
The version of the Compose_From_Polar function without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain.
|
Followed.
4 Implementation Defined Characteristics
In addition to the implementation dependent pragmas and attributes, and
the implementation advice, there are a number of other features of Ada
95 that are potentially implementation dependent. These are mentioned
throughout the Ada 95 Reference Manual, and are summarized in annex M.
A requirement for conforming Ada compilers is that they provide
documentation describing how the implementation deals with each of these
issues. In this chapter, you will find each point in annex M listed
followed by a description in italic font of how GNAT
handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation
dependent features in your programs if portability to other compilers
and other operating systems is an important consideration. The numbers
in each section below correspond to the paragraph number in the Ada 95
Reference Manual.
|
2. Whether or not each recommendation given in Implementation
Advice is followed. See 1.1.2(37).
|
See Implementation Advice.
|
3. Capacity limitations of the implementation. See 1.1.3(3).
|
The complexity of programs that can be processed is limited only by the
total amount of available virtual memory, and disk space for the
generated object files.
|
4. Variations from the standard that are impractical to avoid
given the implementation's execution environment. See 1.1.3(6).
|
There are no variations from the standard.
5. Which code_statements cause external
interactions. See 1.1.3(10).
|
Any code_statement can potentially cause external "cartouche" border="1">
If implementation-defined forms of interrupt handler procedures are
supported, such as protected procedures with parameters, then for each
such form of a handler, a type analogous to Parameterless_Handler
should be specified in a child package of Interrupts, with the
same operations as in the predefined package Interrupts.
|
Followed.
C.4(14): Pre-elaboration Requirements
|
It is recommended that pre-elaborated packages be implemented in such a
way that there should be little or no code executed at run time for the
elaboration of entities not already covered by the Implementation
Requirements.
|
Followed. Executable code is generated in some cases, e.g. loops
to initialize large arrays.
C.5(8): Pragma Discard_Names
|
If the pragma applies to an entity, then the implementation should
reduce the amount of storage used for storing names associated with that
entity.
|
Followed.
C.7.2(30): The Package Task_Attributes
|
Some implementations are targeted to domains in which memory use at run
time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first N
attribute objects, and the heap for the others. In the latter case,
N should be documented.
|
Not followed. This implementation is not targeted to such a domain.
D.3(17): Locking Policies
|
The implementation should use names that end with _Locking for
locking policies defined by the implementation.
|
Followed. A single implementation-defined locking policy is defined,
whose name (Inheritance_Locking) follows this suggestion.
D.4(16): Entry Queuing Policies
|
Names that end with _Queuing should be used
for all implementation-defined queuing policies.
|
Followed. No such implementation-defined queuing policies exist.
D.6(9-10): Preemptive Abort
Even though the abort_statement is included in the list of
potentially blocking operations (see 9.5.1), it is recommended that this
statement be implemented in a way that never requires the task executing
the abort_statement to block.
|
Followed.
|
On a multi-processor, the delay associated with aborting a task on
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
|
Followed.
D.7(21): Tasking Restrictions
|
When feasible, the implementation should take advantage of the specified
restrictions to produce a more efficient implementation.
|
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
of restrictions are specified. See pragma Ravenscar and pragma
Restricted_Run_Time for more details.
D.8(47-49): Monotonic Time
When appropriate, implementations should provide configuration
mechanisms to change the value of Tick.
|
Such configuration mechanisms are not appropriate to this implementation
and are thus not supported.
It is recommended that Calendar.Clock and Real_Time.Clock
be implemented as transformations of the same time base.
|
Followed.
It is recommended that the best time base which exists in
the underlying system be available to the application through
Clock. Best may mean highest accuracy or largest range.
|
Followed.
E.5(28-29): Partition Communication Subsystem
|
Whenever possible, the PCS on the called partition should allow for
multiple tasks to call the RPC-receiver with different messages and
should allow them to block until the corresponding subprogram body
returns.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
The Write operation on a stream of type Params_Stream_Type
should raise Storage_Error if it runs out of space trying to
write the Item into the stream.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
F(7): COBOL Support
If COBOL (respectively, C) is widely supported in the target
environment, implementations supporting the Information Systems Annex
should provide the child package Interfaces.COBOL (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of COBOL (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
F.1(2): Decimal Radix Support
|
Packed decimal should be used as the internal representation for objects
of subtype S when S'Machine_Radix = 10.
|
Not followed. GNAT ignores S'Machine_Radix and always uses binary
representations.
G: Numerics
If Fortran (respectively, C) is widely supported in the target
environment, implementations supporting the Numerics Annex
should provide the child package Interfaces.Fortran (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of Fortran (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
G.1.1(56-58): Complex Types
|
Because the usual mathematical meaning of multiplication of a complex
operand and a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
|
Not followed.
Similarly, because the usual mathematical meaning of addition of a
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
complex addition. In implementations in which the Signed_Zeros
attribute of the component type is True (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
|
Not followed.
Implementations in which Real'Signed_Zeros is True should
attempt to provide a rational treatment of the signs of zero results and
result components. As one example, the result of the Argument
function should have the sign of the imaginary component of the
parameter X when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
of the Compose_From_Polar function should be the same as
(respectively, the opposite of) that of the Argument parameter when that
parameter has a value of zero and the Modulus parameter has a
nonnegative (respectively, negative) value.
|
Followed.
G.1.2(49): Complex Elementary Functions
Implementations in which Complex_Types.Real'Signed_Zeros is
True should attempt to provide a rational treatment of the signs
of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
a parameter component at the origin, or is always positive or always
negative.
|
Followed.
G.2.4(19): Accuracy Requirements
The versions of the forward trigonometric functions without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain. For the same reason, the
version of Log without a Base parameter should not be
implemented by calling the corresponding version with a Base
parameter of Numerics.e.
|
Followed.
G.2.6(15): Complex Arithmetic Accuracy
The version of the Compose_From_Polar function without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain.
|
Followed.
4 Implementation Defined Characteristics
In addition to the implementation dependent pragmas and attributes, and
the implementation advice, there are a number of other features of Ada
95 that are potentially implementation dependent. These are mentioned
throughout the Ada 95 Reference Manual, and are summarized in annex M.
A requirement for conforming Ada compilers is that they provide
documentation describing how the implementation deals with each of these
issues. In this chapter, you will find each point in annex M listed
followed by a description in italic font of how GNAT
handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation
dependent features in your programs if portability to other compilers
and other operating systems is an important consideration. The numbers
in each section below correspond to the paragraph number in the Ada 95
Reference Manual.
|
2. Whether or not each recommendation given in Implementation
Advice is followed. See 1.1.2(37).
|
See Implementation Advice.
|
3. Capacity limitations of the implementation. See 1.1.3(3).
|
The complexity of programs that can be processed is limited only by the
total amount of available virtual memory, and disk space for the
generated object files.
|
4. Variations from the standard that are impractical to avoid
given the implementation's execution environment. See 1.1.3(6).
|
There are no variations from the standard.
5. Which code_statements cause external
interactions. See 1.1.3(10).
|
Any code_statement can potentially cause external "cartouche" border="1">
If implementation-defined forms of interrupt handler procedures are
supported, such as protected procedures with parameters, then for each
such form of a handler, a type analogous to Parameterless_Handler
should be specified in a child package of Interrupts, with the
same operations as in the predefined package Interrupts.
|
Followed.
C.4(14): Pre-elaboration Requirements
|
It is recommended that pre-elaborated packages be implemented in such a
way that there should be little or no code executed at run time for the
elaboration of entities not already covered by the Implementation
Requirements.
|
Followed. Executable code is generated in some cases, e.g. loops
to initialize large arrays.
C.5(8): Pragma Discard_Names
|
If the pragma applies to an entity, then the implementation should
reduce the amount of storage used for storing names associated with that
entity.
|
Followed.
C.7.2(30): The Package Task_Attributes
|
Some implementations are targeted to domains in which memory use at run
time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first N
attribute objects, and the heap for the others. In the latter case,
N should be documented.
|
Not followed. This implementation is not targeted to such a domain.
D.3(17): Locking Policies
|
The implementation should use names that end with _Locking for
locking policies defined by the implementation.
|
Followed. A single implementation-defined locking policy is defined,
whose name (Inheritance_Locking) follows this suggestion.
D.4(16): Entry Queuing Policies
|
Names that end with _Queuing should be used
for all implementation-defined queuing policies.
|
Followed. No such implementation-defined queuing policies exist.
D.6(9-10): Preemptive Abort
Even though the abort_statement is included in the list of
potentially blocking operations (see 9.5.1), it is recommended that this
statement be implemented in a way that never requires the task executing
the abort_statement to block.
|
Followed.
|
On a multi-processor, the delay associated with aborting a task on
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
|
Followed.
D.7(21): Tasking Restrictions
|
When feasible, the implementation should take advantage of the specified
restrictions to produce a more efficient implementation.
|
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
of restrictions are specified. See pragma Ravenscar and pragma
Restricted_Run_Time for more details.
D.8(47-49): Monotonic Time
When appropriate, implementations should provide configuration
mechanisms to change the value of Tick.
|
Such configuration mechanisms are not appropriate to this implementation
and are thus not supported.
It is recommended that Calendar.Clock and Real_Time.Clock
be implemented as transformations of the same time base.
|
Followed.
It is recommended that the best time base which exists in
the underlying system be available to the application through
Clock. Best may mean highest accuracy or largest range.
|
Followed.
E.5(28-29): Partition Communication Subsystem
|
Whenever possible, the PCS on the called partition should allow for
multiple tasks to call the RPC-receiver with different messages and
should allow them to block until the corresponding subprogram body
returns.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
The Write operation on a stream of type Params_Stream_Type
should raise Storage_Error if it runs out of space trying to
write the Item into the stream.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
F(7): COBOL Support
If COBOL (respectively, C) is widely supported in the target
environment, implementations supporting the Information Systems Annex
should provide the child package Interfaces.COBOL (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of COBOL (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
F.1(2): Decimal Radix Support
|
Packed decimal should be used as the internal representation for objects
of subtype S when S'Machine_Radix = 10.
|
Not followed. GNAT ignores S'Machine_Radix and always uses binary
representations.
G: Numerics
If Fortran (respectively, C) is widely supported in the target
environment, implementations supporting the Numerics Annex
should provide the child package Interfaces.Fortran (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of Fortran (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
G.1.1(56-58): Complex Types
|
Because the usual mathematical meaning of multiplication of a complex
operand and a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
|
Not followed.
Similarly, because the usual mathematical meaning of addition of a
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
complex addition. In implementations in which the Signed_Zeros
attribute of the component type is True (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
|
Not followed.
Implementations in which Real'Signed_Zeros is True should
attempt to provide a rational treatment of the signs of zero results and
result components. As one example, the result of the Argument
function should have the sign of the imaginary component of the
parameter X when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
of the Compose_From_Polar function should be the same as
(respectively, the opposite of) that of the Argument parameter when that
parameter has a value of zero and the Modulus parameter has a
nonnegative (respectively, negative) value.
|
Followed.
G.1.2(49): Complex Elementary Functions
Implementations in which Complex_Types.Real'Signed_Zeros is
True should attempt to provide a rational treatment of the signs
of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
a parameter component at the origin, or is always positive or always
negative.
|
Followed.
G.2.4(19): Accuracy Requirements
The versions of the forward trigonometric functions without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain. For the same reason, the
version of Log without a Base parameter should not be
implemented by calling the corresponding version with a Base
parameter of Numerics.e.
|
Followed.
G.2.6(15): Complex Arithmetic Accuracy
The version of the Compose_From_Polar function without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain.
|
Followed.
4 Implementation Defined Characteristics
In addition to the implementation dependent pragmas and attributes, and
the implementation advice, there are a number of other features of Ada
95 that are potentially implementation dependent. These are mentioned
throughout the Ada 95 Reference Manual, and are summarized in annex M.
A requirement for conforming Ada compilers is that they provide
documentation describing how the implementation deals with each of these
issues. In this chapter, you will find each point in annex M listed
followed by a description in italic font of how GNAT
handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation
dependent features in your programs if portability to other compilers
and other operating systems is an important consideration. The numbers
in each section below correspond to the paragraph number in the Ada 95
Reference Manual.
|
2. Whether or not each recommendation given in Implementation
Advice is followed. See 1.1.2(37).
|
See Implementation Advice.
|
3. Capacity limitations of the implementation. See 1.1.3(3).
|
The complexity of programs that can be processed is limited only by the
total amount of available virtual memory, and disk space for the
generated object files.
|
4. Variations from the standard that are impractical to avoid
given the implementation's execution environment. See 1.1.3(6).
|
There are no variations from the standard.
5. Which code_statements cause external
interactions. See 1.1.3(10).
|
Any code_statement can potentially cause external "cartouche" border="1">
If implementation-defined forms of interrupt handler procedures are
supported, such as protected procedures with parameters, then for each
such form of a handler, a type analogous to Parameterless_Handler
should be specified in a child package of Interrupts, with the
same operations as in the predefined package Interrupts.
|
Followed.
C.4(14): Pre-elaboration Requirements
|
It is recommended that pre-elaborated packages be implemented in such a
way that there should be little or no code executed at run time for the
elaboration of entities not already covered by the Implementation
Requirements.
|
Followed. Executable code is generated in some cases, e.g. loops
to initialize large arrays.
C.5(8): Pragma Discard_Names
|
If the pragma applies to an entity, then the implementation should
reduce the amount of storage used for storing names associated with that
entity.
|
Followed.
C.7.2(30): The Package Task_Attributes
|
Some implementations are targeted to domains in which memory use at run
time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first N
attribute objects, and the heap for the others. In the latter case,
N should be documented.
|
Not followed. This implementation is not targeted to such a domain.
D.3(17): Locking Policies
|
The implementation should use names that end with _Locking for
locking policies defined by the implementation.
|
Followed. A single implementation-defined locking policy is defined,
whose name (Inheritance_Locking) follows this suggestion.
D.4(16): Entry Queuing Policies
|
Names that end with _Queuing should be used
for all implementation-defined queuing policies.
|
Followed. No such implementation-defined queuing policies exist.
D.6(9-10): Preemptive Abort
Even though the abort_statement is included in the list of
potentially blocking operations (see 9.5.1), it is recommended that this
statement be implemented in a way that never requires the task executing
the abort_statement to block.
|
Followed.
|
On a multi-processor, the delay associated with aborting a task on
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
|
Followed.
D.7(21): Tasking Restrictions
|
When feasible, the implementation should take advantage of the specified
restrictions to produce a more efficient implementation.
|
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
of restrictions are specified. See pragma Ravenscar and pragma
Restricted_Run_Time for more details.
D.8(47-49): Monotonic Time
When appropriate, implementations should provide configuration
mechanisms to change the value of Tick.
|
Such configuration mechanisms are not appropriate to this implementation
and are thus not supported.
It is recommended that Calendar.Clock and Real_Time.Clock
be implemented as transformations of the same time base.
|
Followed.
It is recommended that the best time base which exists in
the underlying system be available to the application through
Clock. Best may mean highest accuracy or largest range.
|
Followed.
E.5(28-29): Partition Communication Subsystem
|
Whenever possible, the PCS on the called partition should allow for
multiple tasks to call the RPC-receiver with different messages and
should allow them to block until the corresponding subprogram body
returns.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
The Write operation on a stream of type Params_Stream_Type
should raise Storage_Error if it runs out of space trying to
write the Item into the stream.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
F(7): COBOL Support
If COBOL (respectively, C) is widely supported in the target
environment, implementations supporting the Information Systems Annex
should provide the child package Interfaces.COBOL (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of COBOL (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
F.1(2): Decimal Radix Support
|
Packed decimal should be used as the internal representation for objects
of subtype S when S'Machine_Radix = 10.
|
Not followed. GNAT ignores S'Machine_Radix and always uses binary
representations.
G: Numerics
If Fortran (respectively, C) is widely supported in the target
environment, implementations supporting the Numerics Annex
should provide the child package Interfaces.Fortran (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of Fortran (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
G.1.1(56-58): Complex Types
|
Because the usual mathematical meaning of multiplication of a complex
operand and a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
|
Not followed.
Similarly, because the usual mathematical meaning of addition of a
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
complex addition. In implementations in which the Signed_Zeros
attribute of the component type is True (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
|
Not followed.
Implementations in which Real'Signed_Zeros is True should
attempt to provide a rational treatment of the signs of zero results and
result components. As one example, the result of the Argument
function should have the sign of the imaginary component of the
parameter X when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
of the Compose_From_Polar function should be the same as
(respectively, the opposite of) that of the Argument parameter when that
parameter has a value of zero and the Modulus parameter has a
nonnegative (respectively, negative) value.
|
Followed.
G.1.2(49): Complex Elementary Functions
Implementations in which Complex_Types.Real'Signed_Zeros is
True should attempt to provide a rational treatment of the signs
of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
a parameter component at the origin, or is always positive or always
negative.
|
Followed.
G.2.4(19): Accuracy Requirements
The versions of the forward trigonometric functions without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain. For the same reason, the
version of Log without a Base parameter should not be
implemented by calling the corresponding version with a Base
parameter of Numerics.e.
|
Followed.
G.2.6(15): Complex Arithmetic Accuracy
The version of the Compose_From_Polar function without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain.
|
Followed.
4 Implementation Defined Characteristics
In addition to the implementation dependent pragmas and attributes, and
the implementation advice, there are a number of other features of Ada
95 that are potentially implementation dependent. These are mentioned
throughout the Ada 95 Reference Manual, and are summarized in annex M.
A requirement for conforming Ada compilers is that they provide
documentation describing how the implementation deals with each of these
issues. In this chapter, you will find each point in annex M listed
followed by a description in italic font of how GNAT
handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation
dependent features in your programs if portability to other compilers
and other operating systems is an important consideration. The numbers
in each section below correspond to the paragraph number in the Ada 95
Reference Manual.
|
2. Whether or not each recommendation given in Implementation
Advice is followed. See 1.1.2(37).
|
See Implementation Advice.
|
3. Capacity limitations of the implementation. See 1.1.3(3).
|
The complexity of programs that can be processed is limited only by the
total amount of available virtual memory, and disk space for the
generated object files.
|
4. Variations from the standard that are impractical to avoid
given the implementation's execution environment. See 1.1.3(6).
|
There are no variations from the standard.
5. Which code_statements cause external
interactions. See 1.1.3(10).
|
Any code_statement can potentially cause external "cartouche" border="1">
If implementation-defined forms of interrupt handler procedures are
supported, such as protected procedures with parameters, then for each
such form of a handler, a type analogous to Parameterless_Handler
should be specified in a child package of Interrupts, with the
same operations as in the predefined package Interrupts.
|
Followed.
C.4(14): Pre-elaboration Requirements
|
It is recommended that pre-elaborated packages be implemented in such a
way that there should be little or no code executed at run time for the
elaboration of entities not already covered by the Implementation
Requirements.
|
Followed. Executable code is generated in some cases, e.g. loops
to initialize large arrays.
C.5(8): Pragma Discard_Names
|
If the pragma applies to an entity, then the implementation should
reduce the amount of storage used for storing names associated with that
entity.
|
Followed.
C.7.2(30): The Package Task_Attributes
|
Some implementations are targeted to domains in which memory use at run
time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first N
attribute objects, and the heap for the others. In the latter case,
N should be documented.
|
Not followed. This implementation is not targeted to such a domain.
D.3(17): Locking Policies
|
The implementation should use names that end with _Locking for
locking policies defined by the implementation.
|
Followed. A single implementation-defined locking policy is defined,
whose name (Inheritance_Locking) follows this suggestion.
D.4(16): Entry Queuing Policies
|
Names that end with _Queuing should be used
for all implementation-defined queuing policies.
|
Followed. No such implementation-defined queuing policies exist.
D.6(9-10): Preemptive Abort
Even though the abort_statement is included in the list of
potentially blocking operations (see 9.5.1), it is recommended that this
statement be implemented in a way that never requires the task executing
the abort_statement to block.
|
Followed.
|
On a multi-processor, the delay associated with aborting a task on
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
|
Followed.
D.7(21): Tasking Restrictions
|
When feasible, the implementation should take advantage of the specified
restrictions to produce a more efficient implementation.
|
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
of restrictions are specified. See pragma Ravenscar and pragma
Restricted_Run_Time for more details.
D.8(47-49): Monotonic Time
When appropriate, implementations should provide configuration
mechanisms to change the value of Tick.
|
Such configuration mechanisms are not appropriate to this implementation
and are thus not supported.
It is recommended that Calendar.Clock and Real_Time.Clock
be implemented as transformations of the same time base.
|
Followed.
It is recommended that the best time base which exists in
the underlying system be available to the application through
Clock. Best may mean highest accuracy or largest range.
|
Followed.
E.5(28-29): Partition Communication Subsystem
|
Whenever possible, the PCS on the called partition should allow for
multiple tasks to call the RPC-receiver with different messages and
should allow them to block until the corresponding subprogram body
returns.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
The Write operation on a stream of type Params_Stream_Type
should raise Storage_Error if it runs out of space trying to
write the Item into the stream.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
F(7): COBOL Support
If COBOL (respectively, C) is widely supported in the target
environment, implementations supporting the Information Systems Annex
should provide the child package Interfaces.COBOL (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of COBOL (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
F.1(2): Decimal Radix Support
|
Packed decimal should be used as the internal representation for objects
of subtype S when S'Machine_Radix = 10.
|
Not followed. GNAT ignores S'Machine_Radix and always uses binary
representations.
G: Numerics
If Fortran (respectively, C) is widely supported in the target
environment, implementations supporting the Numerics Annex
should provide the child package Interfaces.Fortran (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of Fortran (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
G.1.1(56-58): Complex Types
|
Because the usual mathematical meaning of multiplication of a complex
operand and a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
|
Not followed.
Similarly, because the usual mathematical meaning of addition of a
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
complex addition. In implementations in which the Signed_Zeros
attribute of the component type is True (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
|
Not followed.
Implementations in which Real'Signed_Zeros is True should
attempt to provide a rational treatment of the signs of zero results and
result components. As one example, the result of the Argument
function should have the sign of the imaginary component of the
parameter X when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
of the Compose_From_Polar function should be the same as
(respectively, the opposite of) that of the Argument parameter when that
parameter has a value of zero and the Modulus parameter has a
nonnegative (respectively, negative) value.
|
Followed.
G.1.2(49): Complex Elementary Functions
Implementations in which Complex_Types.Real'Signed_Zeros is
True should attempt to provide a rational treatment of the signs
of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
a parameter component at the origin, or is always positive or always
negative.
|
Followed.
G.2.4(19): Accuracy Requirements
The versions of the forward trigonometric functions without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain. For the same reason, the
version of Log without a Base parameter should not be
implemented by calling the corresponding version with a Base
parameter of Numerics.e.
|
Followed.
G.2.6(15): Complex Arithmetic Accuracy
The version of the Compose_From_Polar function without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain.
|
Followed.
4 Implementation Defined Characteristics
In addition to the implementation dependent pragmas and attributes, and
the implementation advice, there are a number of other features of Ada
95 that are potentially implementation dependent. These are mentioned
throughout the Ada 95 Reference Manual, and are summarized in annex M.
A requirement for conforming Ada compilers is that they provide
documentation describing how the implementation deals with each of these
issues. In this chapter, you will find each point in annex M listed
followed by a description in italic font of how GNAT
handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation
dependent features in your programs if portability to other compilers
and other operating systems is an important consideration. The numbers
in each section below correspond to the paragraph number in the Ada 95
Reference Manual.
|
2. Whether or not each recommendation given in Implementation
Advice is followed. See 1.1.2(37).
|
See Implementation Advice.
|
3. Capacity limitations of the implementation. See 1.1.3(3).
|
The complexity of programs that can be processed is limited only by the
total amount of available virtual memory, and disk space for the
generated object files.
|
4. Variations from the standard that are impractical to avoid
given the implementation's execution environment. See 1.1.3(6).
|
There are no variations from the standard.
5. Which code_statements cause external
interactions. See 1.1.3(10).
|
Any code_statement can potentially cause external "cartouche" border="1">
If implementation-defined forms of interrupt handler procedures are
supported, such as protected procedures with parameters, then for each
such form of a handler, a type analogous to Parameterless_Handler
should be specified in a child package of Interrupts, with the
same operations as in the predefined package Interrupts.
|
Followed.
C.4(14): Pre-elaboration Requirements
|
It is recommended that pre-elaborated packages be implemented in such a
way that there should be little or no code executed at run time for the
elaboration of entities not already covered by the Implementation
Requirements.
|
Followed. Executable code is generated in some cases, e.g. loops
to initialize large arrays.
C.5(8): Pragma Discard_Names
|
If the pragma applies to an entity, then the implementation should
reduce the amount of storage used for storing names associated with that
entity.
|
Followed.
C.7.2(30): The Package Task_Attributes
|
Some implementations are targeted to domains in which memory use at run
time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first N
attribute objects, and the heap for the others. In the latter case,
N should be documented.
|
Not followed. This implementation is not targeted to such a domain.
D.3(17): Locking Policies
|
The implementation should use names that end with _Locking for
locking policies defined by the implementation.
|
Followed. A single implementation-defined locking policy is defined,
whose name (Inheritance_Locking) follows this suggestion.
D.4(16): Entry Queuing Policies
|
Names that end with _Queuing should be used
for all implementation-defined queuing policies.
|
Followed. No such implementation-defined queuing policies exist.
D.6(9-10): Preemptive Abort
Even though the abort_statement is included in the list of
potentially blocking operations (see 9.5.1), it is recommended that this
statement be implemented in a way that never requires the task executing
the abort_statement to block.
|
Followed.
|
On a multi-processor, the delay associated with aborting a task on
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
|
Followed.
D.7(21): Tasking Restrictions
|
When feasible, the implementation should take advantage of the specified
restrictions to produce a more efficient implementation.
|
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
of restrictions are specified. See pragma Ravenscar and pragma
Restricted_Run_Time for more details.
D.8(47-49): Monotonic Time
When appropriate, implementations should provide configuration
mechanisms to change the value of Tick.
|
Such configuration mechanisms are not appropriate to this implementation
and are thus not supported.
It is recommended that Calendar.Clock and Real_Time.Clock
be implemented as transformations of the same time base.
|
Followed.
It is recommended that the best time base which exists in
the underlying system be available to the application through
Clock. Best may mean highest accuracy or largest range.
|
Followed.
E.5(28-29): Partition Communication Subsystem
|
Whenever possible, the PCS on the called partition should allow for
multiple tasks to call the RPC-receiver with different messages and
should allow them to block until the corresponding subprogram body
returns.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
The Write operation on a stream of type Params_Stream_Type
should raise Storage_Error if it runs out of space trying to
write the Item into the stream.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
F(7): COBOL Support
If COBOL (respectively, C) is widely supported in the target
environment, implementations supporting the Information Systems Annex
should provide the child package Interfaces.COBOL (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of COBOL (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
F.1(2): Decimal Radix Support
|
Packed decimal should be used as the internal representation for objects
of subtype S when S'Machine_Radix = 10.
|
Not followed. GNAT ignores S'Machine_Radix and always uses binary
representations.
G: Numerics
If Fortran (respectively, C) is widely supported in the target
environment, implementations supporting the Numerics Annex
should provide the child package Interfaces.Fortran (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of Fortran (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
G.1.1(56-58): Complex Types
|
Because the usual mathematical meaning of multiplication of a complex
operand and a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
|
Not followed.
Similarly, because the usual mathematical meaning of addition of a
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
complex addition. In implementations in which the Signed_Zeros
attribute of the component type is True (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
|
Not followed.
Implementations in which Real'Signed_Zeros is True should
attempt to provide a rational treatment of the signs of zero results and
result components. As one example, the result of the Argument
function should have the sign of the imaginary component of the
parameter X when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
of the Compose_From_Polar function should be the same as
(respectively, the opposite of) that of the Argument parameter when that
parameter has a value of zero and the Modulus parameter has a
nonnegative (respectively, negative) value.
|
Followed.
G.1.2(49): Complex Elementary Functions
Implementations in which Complex_Types.Real'Signed_Zeros is
True should attempt to provide a rational treatment of the signs
of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
a parameter component at the origin, or is always positive or always
negative.
|
Followed.
G.2.4(19): Accuracy Requirements
The versions of the forward trigonometric functions without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain. For the same reason, the
version of Log without a Base parameter should not be
implemented by calling the corresponding version with a Base
parameter of Numerics.e.
|
Followed.
G.2.6(15): Complex Arithmetic Accuracy
The version of the Compose_From_Polar function without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain.
|
Followed.
4 Implementation Defined Characteristics
In addition to the implementation dependent pragmas and attributes, and
the implementation advice, there are a number of other features of Ada
95 that are potentially implementation dependent. These are mentioned
throughout the Ada 95 Reference Manual, and are summarized in annex M.
A requirement for conforming Ada compilers is that they provide
documentation describing how the implementation deals with each of these
issues. In this chapter, you will find each point in annex M listed
followed by a description in italic font of how GNAT
handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation
dependent features in your programs if portability to other compilers
and other operating systems is an important consideration. The numbers
in each section below correspond to the paragraph number in the Ada 95
Reference Manual.
|
2. Whether or not each recommendation given in Implementation
Advice is followed. See 1.1.2(37).
|
See Implementation Advice.
|
3. Capacity limitations of the implementation. See 1.1.3(3).
|
The complexity of programs that can be processed is limited only by the
total amount of available virtual memory, and disk space for the
generated object files.
|
4. Variations from the standard that are impractical to avoid
given the implementation's execution environment. See 1.1.3(6).
|
There are no variations from the standard.
5. Which code_statements cause external
interactions. See 1.1.3(10).
|
Any code_statement can potentially cause external "cartouche" border="1">
If implementation-defined forms of interrupt handler procedures are
supported, such as protected procedures with parameters, then for each
such form of a handler, a type analogous to Parameterless_Handler
should be specified in a child package of Interrupts, with the
same operations as in the predefined package Interrupts.
|
Followed.
C.4(14): Pre-elaboration Requirements
|
It is recommended that pre-elaborated packages be implemented in such a
way that there should be little or no code executed at run time for the
elaboration of entities not already covered by the Implementation
Requirements.
|
Followed. Executable code is generated in some cases, e.g. loops
to initialize large arrays.
C.5(8): Pragma Discard_Names
|
If the pragma applies to an entity, then the implementation should
reduce the amount of storage used for storing names associated with that
entity.
|
Followed.
C.7.2(30): The Package Task_Attributes
|
Some implementations are targeted to domains in which memory use at run
time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first N
attribute objects, and the heap for the others. In the latter case,
N should be documented.
|
Not followed. This implementation is not targeted to such a domain.
D.3(17): Locking Policies
|
The implementation should use names that end with _Locking for
locking policies defined by the implementation.
|
Followed. A single implementation-defined locking policy is defined,
whose name (Inheritance_Locking) follows this suggestion.
D.4(16): Entry Queuing Policies
|
Names that end with _Queuing should be used
for all implementation-defined queuing policies.
|
Followed. No such implementation-defined queuing policies exist.
D.6(9-10): Preemptive Abort
Even though the abort_statement is included in the list of
potentially blocking operations (see 9.5.1), it is recommended that this
statement be implemented in a way that never requires the task executing
the abort_statement to block.
|
Followed.
|
On a multi-processor, the delay associated with aborting a task on
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
|
Followed.
D.7(21): Tasking Restrictions
|
When feasible, the implementation should take advantage of the specified
restrictions to produce a more efficient implementation.
|
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
of restrictions are specified. See pragma Ravenscar and pragma
Restricted_Run_Time for more details.
D.8(47-49): Monotonic Time
When appropriate, implementations should provide configuration
mechanisms to change the value of Tick.
|
Such configuration mechanisms are not appropriate to this implementation
and are thus not supported.
It is recommended that Calendar.Clock and Real_Time.Clock
be implemented as transformations of the same time base.
|
Followed.
It is recommended that the best time base which exists in
the underlying system be available to the application through
Clock. Best may mean highest accuracy or largest range.
|
Followed.
E.5(28-29): Partition Communication Subsystem
|
Whenever possible, the PCS on the called partition should allow for
multiple tasks to call the RPC-receiver with different messages and
should allow them to block until the corresponding subprogram body
returns.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
The Write operation on a stream of type Params_Stream_Type
should raise Storage_Error if it runs out of space trying to
write the Item into the stream.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
F(7): COBOL Support
If COBOL (respectively, C) is widely supported in the target
environment, implementations supporting the Information Systems Annex
should provide the child package Interfaces.COBOL (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of COBOL (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
F.1(2): Decimal Radix Support
|
Packed decimal should be used as the internal representation for objects
of subtype S when S'Machine_Radix = 10.
|
Not followed. GNAT ignores S'Machine_Radix and always uses binary
representations.
G: Numerics
If Fortran (respectively, C) is widely supported in the target
environment, implementations supporting the Numerics Annex
should provide the child package Interfaces.Fortran (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of Fortran (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
G.1.1(56-58): Complex Types
|
Because the usual mathematical meaning of multiplication of a complex
operand and a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
|
Not followed.
Similarly, because the usual mathematical meaning of addition of a
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
complex addition. In implementations in which the Signed_Zeros
attribute of the component type is True (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
|
Not followed.
Implementations in which Real'Signed_Zeros is True should
attempt to provide a rational treatment of the signs of zero results and
result components. As one example, the result of the Argument
function should have the sign of the imaginary component of the
parameter X when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
of the Compose_From_Polar function should be the same as
(respectively, the opposite of) that of the Argument parameter when that
parameter has a value of zero and the Modulus parameter has a
nonnegative (respectively, negative) value.
|
Followed.
G.1.2(49): Complex Elementary Functions
Implementations in which Complex_Types.Real'Signed_Zeros is
True should attempt to provide a rational treatment of the signs
of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
a parameter component at the origin, or is always positive or always
negative.
|
Followed.
G.2.4(19): Accuracy Requirements
The versions of the forward trigonometric functions without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain. For the same reason, the
version of Log without a Base parameter should not be
implemented by calling the corresponding version with a Base
parameter of Numerics.e.
|
Followed.
G.2.6(15): Complex Arithmetic Accuracy
The version of the Compose_From_Polar function without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain.
|
Followed.
4 Implementation Defined Characteristics
In addition to the implementation dependent pragmas and attributes, and
the implementation advice, there are a number of other features of Ada
95 that are potentially implementation dependent. These are mentioned
throughout the Ada 95 Reference Manual, and are summarized in annex M.
A requirement for conforming Ada compilers is that they provide
documentation describing how the implementation deals with each of these
issues. In this chapter, you will find each point in annex M listed
followed by a description in italic font of how GNAT
handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation
dependent features in your programs if portability to other compilers
and other operating systems is an important consideration. The numbers
in each section below correspond to the paragraph number in the Ada 95
Reference Manual.
|
2. Whether or not each recommendation given in Implementation
Advice is followed. See 1.1.2(37).
|
See Implementation Advice.
|
3. Capacity limitations of the implementation. See 1.1.3(3).
|
The complexity of programs that can be processed is limited only by the
total amount of available virtual memory, and disk space for the
generated object files.
|
4. Variations from the standard that are impractical to avoid
given the implementation's execution environment. See 1.1.3(6).
|
There are no variations from the standard.
5. Which code_statements cause external
interactions. See 1.1.3(10).
|
Any code_statement can potentially cause external "cartouche" border="1">
If implementation-defined forms of interrupt handler procedures are
supported, such as protected procedures with parameters, then for each
such form of a handler, a type analogous to Parameterless_Handler
should be specified in a child package of Interrupts, with the
same operations as in the predefined package Interrupts.
|
Followed.
C.4(14): Pre-elaboration Requirements
|
It is recommended that pre-elaborated packages be implemented in such a
way that there should be little or no code executed at run time for the
elaboration of entities not already covered by the Implementation
Requirements.
|
Followed. Executable code is generated in some cases, e.g. loops
to initialize large arrays.
C.5(8): Pragma Discard_Names
|
If the pragma applies to an entity, then the implementation should
reduce the amount of storage used for storing names associated with that
entity.
|
Followed.
C.7.2(30): The Package Task_Attributes
|
Some implementations are targeted to domains in which memory use at run
time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first N
attribute objects, and the heap for the others. In the latter case,
N should be documented.
|
Not followed. This implementation is not targeted to such a domain.
D.3(17): Locking Policies
|
The implementation should use names that end with _Locking for
locking policies defined by the implementation.
|
Followed. A single implementation-defined locking policy is defined,
whose name (Inheritance_Locking) follows this suggestion.
D.4(16): Entry Queuing Policies
|
Names that end with _Queuing should be used
for all implementation-defined queuing policies.
|
Followed. No such implementation-defined queuing policies exist.
D.6(9-10): Preemptive Abort
Even though the abort_statement is included in the list of
potentially blocking operations (see 9.5.1), it is recommended that this
statement be implemented in a way that never requires the task executing
the abort_statement to block.
|
Followed.
|
On a multi-processor, the delay associated with aborting a task on
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
|
Followed.
D.7(21): Tasking Restrictions
|
When feasible, the implementation should take advantage of the specified
restrictions to produce a more efficient implementation.
|
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
of restrictions are specified. See pragma Ravenscar and pragma
Restricted_Run_Time for more details.
D.8(47-49): Monotonic Time
When appropriate, implementations should provide configuration
mechanisms to change the value of Tick.
|
Such configuration mechanisms are not appropriate to this implementation
and are thus not supported.
It is recommended that Calendar.Clock and Real_Time.Clock
be implemented as transformations of the same time base.
|
Followed.
It is recommended that the best time base which exists in
the underlying system be available to the application through
Clock. Best may mean highest accuracy or largest range.
|
Followed.
E.5(28-29): Partition Communication Subsystem
|
Whenever possible, the PCS on the called partition should allow for
multiple tasks to call the RPC-receiver with different messages and
should allow them to block until the corresponding subprogram body
returns.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
The Write operation on a stream of type Params_Stream_Type
should raise Storage_Error if it runs out of space trying to
write the Item into the stream.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
F(7): COBOL Support
If COBOL (respectively, C) is widely supported in the target
environment, implementations supporting the Information Systems Annex
should provide the child package Interfaces.COBOL (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of COBOL (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
F.1(2): Decimal Radix Support
|
Packed decimal should be used as the internal representation for objects
of subtype S when S'Machine_Radix = 10.
|
Not followed. GNAT ignores S'Machine_Radix and always uses binary
representations.
G: Numerics
If Fortran (respectively, C) is widely supported in the target
environment, implementations supporting the Numerics Annex
should provide the child package Interfaces.Fortran (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of Fortran (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
G.1.1(56-58): Complex Types
|
Because the usual mathematical meaning of multiplication of a complex
operand and a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
|
Not followed.
Similarly, because the usual mathematical meaning of addition of a
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
complex addition. In implementations in which the Signed_Zeros
attribute of the component type is True (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
|
Not followed.
Implementations in which Real'Signed_Zeros is True should
attempt to provide a rational treatment of the signs of zero results and
result components. As one example, the result of the Argument
function should have the sign of the imaginary component of the
parameter X when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
of the Compose_From_Polar function should be the same as
(respectively, the opposite of) that of the Argument parameter when that
parameter has a value of zero and the Modulus parameter has a
nonnegative (respectively, negative) value.
|
Followed.
G.1.2(49): Complex Elementary Functions
Implementations in which Complex_Types.Real'Signed_Zeros is
True should attempt to provide a rational treatment of the signs
of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
a parameter component at the origin, or is always positive or always
negative.
|
Followed.
G.2.4(19): Accuracy Requirements
The versions of the forward trigonometric functions without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain. For the same reason, the
version of Log without a Base parameter should not be
implemented by calling the corresponding version with a Base
parameter of Numerics.e.
|
Followed.
G.2.6(15): Complex Arithmetic Accuracy
The version of the Compose_From_Polar function without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain.
|
Followed.
4 Implementation Defined Characteristics
In addition to the implementation dependent pragmas and attributes, and
the implementation advice, there are a number of other features of Ada
95 that are potentially implementation dependent. These are mentioned
throughout the Ada 95 Reference Manual, and are summarized in annex M.
A requirement for conforming Ada compilers is that they provide
documentation describing how the implementation deals with each of these
issues. In this chapter, you will find each point in annex M listed
followed by a description in italic font of how GNAT
handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation
dependent features in your programs if portability to other compilers
and other operating systems is an important consideration. The numbers
in each section below correspond to the paragraph number in the Ada 95
Reference Manual.
|
2. Whether or not each recommendation given in Implementation
Advice is followed. See 1.1.2(37).
|
See Implementation Advice.
|
3. Capacity limitations of the implementation. See 1.1.3(3).
|
The complexity of programs that can be processed is limited only by the
total amount of available virtual memory, and disk space for the
generated object files.
|
4. Variations from the standard that are impractical to avoid
given the implementation's execution environment. See 1.1.3(6).
|
There are no variations from the standard.
5. Which code_statements cause external
interactions. See 1.1.3(10).
|
Any code_statement can potentially cause external "cartouche" border="1">
If implementation-defined forms of interrupt handler procedures are
supported, such as protected procedures with parameters, then for each
such form of a handler, a type analogous to Parameterless_Handler
should be specified in a child package of Interrupts, with the
same operations as in the predefined package Interrupts.
|
Followed.
C.4(14): Pre-elaboration Requirements
|
It is recommended that pre-elaborated packages be implemented in such a
way that there should be little or no code executed at run time for the
elaboration of entities not already covered by the Implementation
Requirements.
|
Followed. Executable code is generated in some cases, e.g. loops
to initialize large arrays.
C.5(8): Pragma Discard_Names
|
If the pragma applies to an entity, then the implementation should
reduce the amount of storage used for storing names associated with that
entity.
|
Followed.
C.7.2(30): The Package Task_Attributes
|
Some implementations are targeted to domains in which memory use at run
time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first N
attribute objects, and the heap for the others. In the latter case,
N should be documented.
|
Not followed. This implementation is not targeted to such a domain.
D.3(17): Locking Policies
|
The implementation should use names that end with _Locking for
locking policies defined by the implementation.
|
Followed. A single implementation-defined locking policy is defined,
whose name (Inheritance_Locking) follows this suggestion.
D.4(16): Entry Queuing Policies
|
Names that end with _Queuing should be used
for all implementation-defined queuing policies.
|
Followed. No such implementation-defined queuing policies exist.
D.6(9-10): Preemptive Abort
Even though the abort_statement is included in the list of
potentially blocking operations (see 9.5.1), it is recommended that this
statement be implemented in a way that never requires the task executing
the abort_statement to block.
|
Followed.
|
On a multi-processor, the delay associated with aborting a task on
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
|
Followed.
D.7(21): Tasking Restrictions
|
When feasible, the implementation should take advantage of the specified
restrictions to produce a more efficient implementation.
|
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
of restrictions are specified. See pragma Ravenscar and pragma
Restricted_Run_Time for more details.
D.8(47-49): Monotonic Time
When appropriate, implementations should provide configuration
mechanisms to change the value of Tick.
|
Such configuration mechanisms are not appropriate to this implementation
and are thus not supported.
It is recommended that Calendar.Clock and Real_Time.Clock
be implemented as transformations of the same time base.
|
Followed.
It is recommended that the best time base which exists in
the underlying system be available to the application through
Clock. Best may mean highest accuracy or largest range.
|
Followed.
E.5(28-29): Partition Communication Subsystem
|
Whenever possible, the PCS on the called partition should allow for
multiple tasks to call the RPC-receiver with different messages and
should allow them to block until the corresponding subprogram body
returns.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
The Write operation on a stream of type Params_Stream_Type
should raise Storage_Error if it runs out of space trying to
write the Item into the stream.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
F(7): COBOL Support
If COBOL (respectively, C) is widely supported in the target
environment, implementations supporting the Information Systems Annex
should provide the child package Interfaces.COBOL (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of COBOL (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
F.1(2): Decimal Radix Support
|
Packed decimal should be used as the internal representation for objects
of subtype S when S'Machine_Radix = 10.
|
Not followed. GNAT ignores S'Machine_Radix and always uses binary
representations.
G: Numerics
If Fortran (respectively, C) is widely supported in the target
environment, implementations supporting the Numerics Annex
should provide the child package Interfaces.Fortran (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of Fortran (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
G.1.1(56-58): Complex Types
|
Because the usual mathematical meaning of multiplication of a complex
operand and a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
|
Not followed.
Similarly, because the usual mathematical meaning of addition of a
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
complex addition. In implementations in which the Signed_Zeros
attribute of the component type is True (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
|
Not followed.
Implementations in which Real'Signed_Zeros is True should
attempt to provide a rational treatment of the signs of zero results and
result components. As one example, the result of the Argument
function should have the sign of the imaginary component of the
parameter X when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
of the Compose_From_Polar function should be the same as
(respectively, the opposite of) that of the Argument parameter when that
parameter has a value of zero and the Modulus parameter has a
nonnegative (respectively, negative) value.
|
Followed.
G.1.2(49): Complex Elementary Functions
Implementations in which Complex_Types.Real'Signed_Zeros is
True should attempt to provide a rational treatment of the signs
of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
a parameter component at the origin, or is always positive or always
negative.
|
Followed.
G.2.4(19): Accuracy Requirements
The versions of the forward trigonometric functions without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain. For the same reason, the
version of Log without a Base parameter should not be
implemented by calling the corresponding version with a Base
parameter of Numerics.e.
|
Followed.
G.2.6(15): Complex Arithmetic Accuracy
The version of the Compose_From_Polar function without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain.
|
Followed.
4 Implementation Defined Characteristics
In addition to the implementation dependent pragmas and attributes, and
the implementation advice, there are a number of other features of Ada
95 that are potentially implementation dependent. These are mentioned
throughout the Ada 95 Reference Manual, and are summarized in annex M.
A requirement for conforming Ada compilers is that they provide
documentation describing how the implementation deals with each of these
issues. In this chapter, you will find each point in annex M listed
followed by a description in italic font of how GNAT
handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation
dependent features in your programs if portability to other compilers
and other operating systems is an important consideration. The numbers
in each section below correspond to the paragraph number in the Ada 95
Reference Manual.
|
2. Whether or not each recommendation given in Implementation
Advice is followed. See 1.1.2(37).
|
See Implementation Advice.
|
3. Capacity limitations of the implementation. See 1.1.3(3).
|
The complexity of programs that can be processed is limited only by the
total amount of available virtual memory, and disk space for the
generated object files.
|
4. Variations from the standard that are impractical to avoid
given the implementation's execution environment. See 1.1.3(6).
|
There are no variations from the standard.
5. Which code_statements cause external
interactions. See 1.1.3(10).
|
Any code_statement can potentially cause external "cartouche" border="1">
If implementation-defined forms of interrupt handler procedures are
supported, such as protected procedures with parameters, then for each
such form of a handler, a type analogous to Parameterless_Handler
should be specified in a child package of Interrupts, with the
same operations as in the predefined package Interrupts.
|
Followed.
C.4(14): Pre-elaboration Requirements
|
It is recommended that pre-elaborated packages be implemented in such a
way that there should be little or no code executed at run time for the
elaboration of entities not already covered by the Implementation
Requirements.
|
Followed. Executable code is generated in some cases, e.g. loops
to initialize large arrays.
C.5(8): Pragma Discard_Names
|
If the pragma applies to an entity, then the implementation should
reduce the amount of storage used for storing names associated with that
entity.
|
Followed.
C.7.2(30): The Package Task_Attributes
|
Some implementations are targeted to domains in which memory use at run
time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first N
attribute objects, and the heap for the others. In the latter case,
N should be documented.
|
Not followed. This implementation is not targeted to such a domain.
D.3(17): Locking Policies
|
The implementation should use names that end with _Locking for
locking policies defined by the implementation.
|
Followed. A single implementation-defined locking policy is defined,
whose name (Inheritance_Locking) follows this suggestion.
D.4(16): Entry Queuing Policies
|
Names that end with _Queuing should be used
for all implementation-defined queuing policies.
|
Followed. No such implementation-defined queuing policies exist.
D.6(9-10): Preemptive Abort
Even though the abort_statement is included in the list of
potentially blocking operations (see 9.5.1), it is recommended that this
statement be implemented in a way that never requires the task executing
the abort_statement to block.
|
Followed.
|
On a multi-processor, the delay associated with aborting a task on
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
|
Followed.
D.7(21): Tasking Restrictions
|
When feasible, the implementation should take advantage of the specified
restrictions to produce a more efficient implementation.
|
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
of restrictions are specified. See pragma Ravenscar and pragma
Restricted_Run_Time for more details.
D.8(47-49): Monotonic Time
When appropriate, implementations should provide configuration
mechanisms to change the value of Tick.
|
Such configuration mechanisms are not appropriate to this implementation
and are thus not supported.
It is recommended that Calendar.Clock and Real_Time.Clock
be implemented as transformations of the same time base.
|
Followed.
It is recommended that the best time base which exists in
the underlying system be available to the application through
Clock. Best may mean highest accuracy or largest range.
|
Followed.
E.5(28-29): Partition Communication Subsystem
|
Whenever possible, the PCS on the called partition should allow for
multiple tasks to call the RPC-receiver with different messages and
should allow them to block until the corresponding subprogram body
returns.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
The Write operation on a stream of type Params_Stream_Type
should raise Storage_Error if it runs out of space trying to
write the Item into the stream.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
F(7): COBOL Support
If COBOL (respectively, C) is widely supported in the target
environment, implementations supporting the Information Systems Annex
should provide the child package Interfaces.COBOL (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of COBOL (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
F.1(2): Decimal Radix Support
|
Packed decimal should be used as the internal representation for objects
of subtype S when S'Machine_Radix = 10.
|
Not followed. GNAT ignores S'Machine_Radix and always uses binary
representations.
G: Numerics
If Fortran (respectively, C) is widely supported in the target
environment, implementations supporting the Numerics Annex
should provide the child package Interfaces.Fortran (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of Fortran (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
G.1.1(56-58): Complex Types
|
Because the usual mathematical meaning of multiplication of a complex
operand and a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
|
Not followed.
Similarly, because the usual mathematical meaning of addition of a
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
complex addition. In implementations in which the Signed_Zeros
attribute of the component type is True (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
|
Not followed.
Implementations in which Real'Signed_Zeros is True should
attempt to provide a rational treatment of the signs of zero results and
result components. As one example, the result of the Argument
function should have the sign of the imaginary component of the
parameter X when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
of the Compose_From_Polar function should be the same as
(respectively, the opposite of) that of the Argument parameter when that
parameter has a value of zero and the Modulus parameter has a
nonnegative (respectively, negative) value.
|
Followed.
G.1.2(49): Complex Elementary Functions
Implementations in which Complex_Types.Real'Signed_Zeros is
True should attempt to provide a rational treatment of the signs
of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
a parameter component at the origin, or is always positive or always
negative.
|
Followed.
G.2.4(19): Accuracy Requirements
The versions of the forward trigonometric functions without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain. For the same reason, the
version of Log without a Base parameter should not be
implemented by calling the corresponding version with a Base
parameter of Numerics.e.
|
Followed.
G.2.6(15): Complex Arithmetic Accuracy
The version of the Compose_From_Polar function without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain.
|
Followed.
4 Implementation Defined Characteristics
In addition to the implementation dependent pragmas and attributes, and
the implementation advice, there are a number of other features of Ada
95 that are potentially implementation dependent. These are mentioned
throughout the Ada 95 Reference Manual, and are summarized in annex M.
A requirement for conforming Ada compilers is that they provide
documentation describing how the implementation deals with each of these
issues. In this chapter, you will find each point in annex M listed
followed by a description in italic font of how GNAT
handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation
dependent features in your programs if portability to other compilers
and other operating systems is an important consideration. The numbers
in each section below correspond to the paragraph number in the Ada 95
Reference Manual.
|
2. Whether or not each recommendation given in Implementation
Advice is followed. See 1.1.2(37).
|
See Implementation Advice.
|
3. Capacity limitations of the implementation. See 1.1.3(3).
|
The complexity of programs that can be processed is limited only by the
total amount of available virtual memory, and disk space for the
generated object files.
|
4. Variations from the standard that are impractical to avoid
given the implementation's execution environment. See 1.1.3(6).
|
There are no variations from the standard.
5. Which code_statements cause external
interactions. See 1.1.3(10).
|
Any code_statement can potentially cause external "cartouche" border="1">
If implementation-defined forms of interrupt handler procedures are
supported, such as protected procedures with parameters, then for each
such form of a handler, a type analogous to Parameterless_Handler
should be specified in a child package of Interrupts, with the
same operations as in the predefined package Interrupts.
|
Followed.
C.4(14): Pre-elaboration Requirements
|
It is recommended that pre-elaborated packages be implemented in such a
way that there should be little or no code executed at run time for the
elaboration of entities not already covered by the Implementation
Requirements.
|
Followed. Executable code is generated in some cases, e.g. loops
to initialize large arrays.
C.5(8): Pragma Discard_Names
|
If the pragma applies to an entity, then the implementation should
reduce the amount of storage used for storing names associated with that
entity.
|
Followed.
C.7.2(30): The Package Task_Attributes
|
Some implementations are targeted to domains in which memory use at run
time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first N
attribute objects, and the heap for the others. In the latter case,
N should be documented.
|
Not followed. This implementation is not targeted to such a domain.
D.3(17): Locking Policies
|
The implementation should use names that end with _Locking for
locking policies defined by the implementation.
|
Followed. A single implementation-defined locking policy is defined,
whose name (Inheritance_Locking) follows this suggestion.
D.4(16): Entry Queuing Policies
|
Names that end with _Queuing should be used
for all implementation-defined queuing policies.
|
Followed. No such implementation-defined queuing policies exist.
D.6(9-10): Preemptive Abort
Even though the abort_statement is included in the list of
potentially blocking operations (see 9.5.1), it is recommended that this
statement be implemented in a way that never requires the task executing
the abort_statement to block.
|
Followed.
|
On a multi-processor, the delay associated with aborting a task on
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
|
Followed.
D.7(21): Tasking Restrictions
|
When feasible, the implementation should take advantage of the specified
restrictions to produce a more efficient implementation.
|
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
of restrictions are specified. See pragma Ravenscar and pragma
Restricted_Run_Time for more details.
D.8(47-49): Monotonic Time
When appropriate, implementations should provide configuration
mechanisms to change the value of Tick.
|
Such configuration mechanisms are not appropriate to this implementation
and are thus not supported.
It is recommended that Calendar.Clock and Real_Time.Clock
be implemented as transformations of the same time base.
|
Followed.
It is recommended that the best time base which exists in
the underlying system be available to the application through
Clock. Best may mean highest accuracy or largest range.
|
Followed.
E.5(28-29): Partition Communication Subsystem
|
Whenever possible, the PCS on the called partition should allow for
multiple tasks to call the RPC-receiver with different messages and
should allow them to block until the corresponding subprogram body
returns.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
The Write operation on a stream of type Params_Stream_Type
should raise Storage_Error if it runs out of space trying to
write the Item into the stream.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
F(7): COBOL Support
If COBOL (respectively, C) is widely supported in the target
environment, implementations supporting the Information Systems Annex
should provide the child package Interfaces.COBOL (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of COBOL (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
F.1(2): Decimal Radix Support
|
Packed decimal should be used as the internal representation for objects
of subtype S when S'Machine_Radix = 10.
|
Not followed. GNAT ignores S'Machine_Radix and always uses binary
representations.
G: Numerics
If Fortran (respectively, C) is widely supported in the target
environment, implementations supporting the Numerics Annex
should provide the child package Interfaces.Fortran (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of Fortran (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
G.1.1(56-58): Complex Types
|
Because the usual mathematical meaning of multiplication of a complex
operand and a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
|
Not followed.
Similarly, because the usual mathematical meaning of addition of a
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
complex addition. In implementations in which the Signed_Zeros
attribute of the component type is True (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
|
Not followed.
Implementations in which Real'Signed_Zeros is True should
attempt to provide a rational treatment of the signs of zero results and
result components. As one example, the result of the Argument
function should have the sign of the imaginary component of the
parameter X when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
of the Compose_From_Polar function should be the same as
(respectively, the opposite of) that of the Argument parameter when that
parameter has a value of zero and the Modulus parameter has a
nonnegative (respectively, negative) value.
|
Followed.
G.1.2(49): Complex Elementary Functions
Implementations in which Complex_Types.Real'Signed_Zeros is
True should attempt to provide a rational treatment of the signs
of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
a parameter component at the origin, or is always positive or always
negative.
|
Followed.
G.2.4(19): Accuracy Requirements
The versions of the forward trigonometric functions without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain. For the same reason, the
version of Log without a Base parameter should not be
implemented by calling the corresponding version with a Base
parameter of Numerics.e.
|
Followed.
G.2.6(15): Complex Arithmetic Accuracy
The version of the Compose_From_Polar function without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain.
|
Followed.
4 Implementation Defined Characteristics
In addition to the implementation dependent pragmas and attributes, and
the implementation advice, there are a number of other features of Ada
95 that are potentially implementation dependent. These are mentioned
throughout the Ada 95 Reference Manual, and are summarized in annex M.
A requirement for conforming Ada compilers is that they provide
documentation describing how the implementation deals with each of these
issues. In this chapter, you will find each point in annex M listed
followed by a description in italic font of how GNAT
handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation
dependent features in your programs if portability to other compilers
and other operating systems is an important consideration. The numbers
in each section below correspond to the paragraph number in the Ada 95
Reference Manual.
|
2. Whether or not each recommendation given in Implementation
Advice is followed. See 1.1.2(37).
|
See Implementation Advice.
|
3. Capacity limitations of the implementation. See 1.1.3(3).
|
The complexity of programs that can be processed is limited only by the
total amount of available virtual memory, and disk space for the
generated object files.
|
4. Variations from the standard that are impractical to avoid
given the implementation's execution environment. See 1.1.3(6).
|
There are no variations from the standard.
5. Which code_statements cause external
interactions. See 1.1.3(10).
|
Any code_statement can potentially cause external "cartouche" border="1">
If implementation-defined forms of interrupt handler procedures are
supported, such as protected procedures with parameters, then for each
such form of a handler, a type analogous to Parameterless_Handler
should be specified in a child package of Interrupts, with the
same operations as in the predefined package Interrupts.
|
Followed.
C.4(14): Pre-elaboration Requirements
|
It is recommended that pre-elaborated packages be implemented in such a
way that there should be little or no code executed at run time for the
elaboration of entities not already covered by the Implementation
Requirements.
|
Followed. Executable code is generated in some cases, e.g. loops
to initialize large arrays.
C.5(8): Pragma Discard_Names
|
If the pragma applies to an entity, then the implementation should
reduce the amount of storage used for storing names associated with that
entity.
|
Followed.
C.7.2(30): The Package Task_Attributes
|
Some implementations are targeted to domains in which memory use at run
time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first N
attribute objects, and the heap for the others. In the latter case,
N should be documented.
|
Not followed. This implementation is not targeted to such a domain.
D.3(17): Locking Policies
|
The implementation should use names that end with _Locking for
locking policies defined by the implementation.
|
Followed. A single implementation-defined locking policy is defined,
whose name (Inheritance_Locking) follows this suggestion.
D.4(16): Entry Queuing Policies
|
Names that end with _Queuing should be used
for all implementation-defined queuing policies.
|
Followed. No such implementation-defined queuing policies exist.
D.6(9-10): Preemptive Abort
Even though the abort_statement is included in the list of
potentially blocking operations (see 9.5.1), it is recommended that this
statement be implemented in a way that never requires the task executing
the abort_statement to block.
|
Followed.
|
On a multi-processor, the delay associated with aborting a task on
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
|
Followed.
D.7(21): Tasking Restrictions
|
When feasible, the implementation should take advantage of the specified
restrictions to produce a more efficient implementation.
|
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
of restrictions are specified. See pragma Ravenscar and pragma
Restricted_Run_Time for more details.
D.8(47-49): Monotonic Time
When appropriate, implementations should provide configuration
mechanisms to change the value of Tick.
|
Such configuration mechanisms are not appropriate to this implementation
and are thus not supported.
It is recommended that Calendar.Clock and Real_Time.Clock
be implemented as transformations of the same time base.
|
Followed.
It is recommended that the best time base which exists in
the underlying system be available to the application through
Clock. Best may mean highest accuracy or largest range.
|
Followed.
E.5(28-29): Partition Communication Subsystem
|
Whenever possible, the PCS on the called partition should allow for
multiple tasks to call the RPC-receiver with different messages and
should allow them to block until the corresponding subprogram body
returns.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
The Write operation on a stream of type Params_Stream_Type
should raise Storage_Error if it runs out of space trying to
write the Item into the stream.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
F(7): COBOL Support
If COBOL (respectively, C) is widely supported in the target
environment, implementations supporting the Information Systems Annex
should provide the child package Interfaces.COBOL (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of COBOL (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
F.1(2): Decimal Radix Support
|
Packed decimal should be used as the internal representation for objects
of subtype S when S'Machine_Radix = 10.
|
Not followed. GNAT ignores S'Machine_Radix and always uses binary
representations.
G: Numerics
If Fortran (respectively, C) is widely supported in the target
environment, implementations supporting the Numerics Annex
should provide the child package Interfaces.Fortran (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of Fortran (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
G.1.1(56-58): Complex Types
|
Because the usual mathematical meaning of multiplication of a complex
operand and a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
|
Not followed.
Similarly, because the usual mathematical meaning of addition of a
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
complex addition. In implementations in which the Signed_Zeros
attribute of the component type is True (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
|
Not followed.
Implementations in which Real'Signed_Zeros is True should
attempt to provide a rational treatment of the signs of zero results and
result components. As one example, the result of the Argument
function should have the sign of the imaginary component of the
parameter X when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
of the Compose_From_Polar function should be the same as
(respectively, the opposite of) that of the Argument parameter when that
parameter has a value of zero and the Modulus parameter has a
nonnegative (respectively, negative) value.
|
Followed.
G.1.2(49): Complex Elementary Functions
Implementations in which Complex_Types.Real'Signed_Zeros is
True should attempt to provide a rational treatment of the signs
of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
a parameter component at the origin, or is always positive or always
negative.
|
Followed.
G.2.4(19): Accuracy Requirements
The versions of the forward trigonometric functions without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain. For the same reason, the
version of Log without a Base parameter should not be
implemented by calling the corresponding version with a Base
parameter of Numerics.e.
|
Followed.
G.2.6(15): Complex Arithmetic Accuracy
The version of the Compose_From_Polar function without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain.
|
Followed.
4 Implementation Defined Characteristics
In addition to the implementation dependent pragmas and attributes, and
the implementation advice, there are a number of other features of Ada
95 that are potentially implementation dependent. These are mentioned
throughout the Ada 95 Reference Manual, and are summarized in annex M.
A requirement for conforming Ada compilers is that they provide
documentation describing how the implementation deals with each of these
issues. In this chapter, you will find each point in annex M listed
followed by a description in italic font of how GNAT
handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation
dependent features in your programs if portability to other compilers
and other operating systems is an important consideration. The numbers
in each section below correspond to the paragraph number in the Ada 95
Reference Manual.
|
2. Whether or not each recommendation given in Implementation
Advice is followed. See 1.1.2(37).
|
See Implementation Advice.
|
3. Capacity limitations of the implementation. See 1.1.3(3).
|
The complexity of programs that can be processed is limited only by the
total amount of available virtual memory, and disk space for the
generated object files.
|
4. Variations from the standard that are impractical to avoid
given the implementation's execution environment. See 1.1.3(6).
|
There are no variations from the standard.
5. Which code_statements cause external
interactions. See 1.1.3(10).
|
Any code_statement can potentially cause external "cartouche" border="1">
If implementation-defined forms of interrupt handler procedures are
supported, such as protected procedures with parameters, then for each
such form of a handler, a type analogous to Parameterless_Handler
should be specified in a child package of Interrupts, with the
same operations as in the predefined package Interrupts.
|
Followed.
C.4(14): Pre-elaboration Requirements
|
It is recommended that pre-elaborated packages be implemented in such a
way that there should be little or no code executed at run time for the
elaboration of entities not already covered by the Implementation
Requirements.
|
Followed. Executable code is generated in some cases, e.g. loops
to initialize large arrays.
C.5(8): Pragma Discard_Names
|
If the pragma applies to an entity, then the implementation should
reduce the amount of storage used for storing names associated with that
entity.
|
Followed.
C.7.2(30): The Package Task_Attributes
|
Some implementations are targeted to domains in which memory use at run
time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first N
attribute objects, and the heap for the others. In the latter case,
N should be documented.
|
Not followed. This implementation is not targeted to such a domain.
D.3(17): Locking Policies
|
The implementation should use names that end with _Locking for
locking policies defined by the implementation.
|
Followed. A single implementation-defined locking policy is defined,
whose name (Inheritance_Locking) follows this suggestion.
D.4(16): Entry Queuing Policies
|
Names that end with _Queuing should be used
for all implementation-defined queuing policies.
|
Followed. No such implementation-defined queuing policies exist.
D.6(9-10): Preemptive Abort
Even though the abort_statement is included in the list of
potentially blocking operations (see 9.5.1), it is recommended that this
statement be implemented in a way that never requires the task executing
the abort_statement to block.
|
Followed.
|
On a multi-processor, the delay associated with aborting a task on
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
|
Followed.
D.7(21): Tasking Restrictions
|
When feasible, the implementation should take advantage of the specified
restrictions to produce a more efficient implementation.
|
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
of restrictions are specified. See pragma Ravenscar and pragma
Restricted_Run_Time for more details.
D.8(47-49): Monotonic Time
When appropriate, implementations should provide configuration
mechanisms to change the value of Tick.
|
Such configuration mechanisms are not appropriate to this implementation
and are thus not supported.
It is recommended that Calendar.Clock and Real_Time.Clock
be implemented as transformations of the same time base.
|
Followed.
It is recommended that the best time base which exists in
the underlying system be available to the application through
Clock. Best may mean highest accuracy or largest range.
|
Followed.
E.5(28-29): Partition Communication Subsystem
|
Whenever possible, the PCS on the called partition should allow for
multiple tasks to call the RPC-receiver with different messages and
should allow them to block until the corresponding subprogram body
returns.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
The Write operation on a stream of type Params_Stream_Type
should raise Storage_Error if it runs out of space trying to
write the Item into the stream.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
F(7): COBOL Support
If COBOL (respectively, C) is widely supported in the target
environment, implementations supporting the Information Systems Annex
should provide the child package Interfaces.COBOL (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of COBOL (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
F.1(2): Decimal Radix Support
|
Packed decimal should be used as the internal representation for objects
of subtype S when S'Machine_Radix = 10.
|
Not followed. GNAT ignores S'Machine_Radix and always uses binary
representations.
G: Numerics
If Fortran (respectively, C) is widely supported in the target
environment, implementations supporting the Numerics Annex
should provide the child package Interfaces.Fortran (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of Fortran (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
G.1.1(56-58): Complex Types
|
Because the usual mathematical meaning of multiplication of a complex
operand and a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
|
Not followed.
Similarly, because the usual mathematical meaning of addition of a
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
complex addition. In implementations in which the Signed_Zeros
attribute of the component type is True (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
|
Not followed.
Implementations in which Real'Signed_Zeros is True should
attempt to provide a rational treatment of the signs of zero results and
result components. As one example, the result of the Argument
function should have the sign of the imaginary component of the
parameter X when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
of the Compose_From_Polar function should be the same as
(respectively, the opposite of) that of the Argument parameter when that
parameter has a value of zero and the Modulus parameter has a
nonnegative (respectively, negative) value.
|
Followed.
G.1.2(49): Complex Elementary Functions
Implementations in which Complex_Types.Real'Signed_Zeros is
True should attempt to provide a rational treatment of the signs
of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
a parameter component at the origin, or is always positive or always
negative.
|
Followed.
G.2.4(19): Accuracy Requirements
The versions of the forward trigonometric functions without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain. For the same reason, the
version of Log without a Base parameter should not be
implemented by calling the corresponding version with a Base
parameter of Numerics.e.
|
Followed.
G.2.6(15): Complex Arithmetic Accuracy
The version of the Compose_From_Polar function without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain.
|
Followed.
4 Implementation Defined Characteristics
In addition to the implementation dependent pragmas and attributes, and
the implementation advice, there are a number of other features of Ada
95 that are potentially implementation dependent. These are mentioned
throughout the Ada 95 Reference Manual, and are summarized in annex M.
A requirement for conforming Ada compilers is that they provide
documentation describing how the implementation deals with each of these
issues. In this chapter, you will find each point in annex M listed
followed by a description in italic font of how GNAT
handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation
dependent features in your programs if portability to other compilers
and other operating systems is an important consideration. The numbers
in each section below correspond to the paragraph number in the Ada 95
Reference Manual.
|
2. Whether or not each recommendation given in Implementation
Advice is followed. See 1.1.2(37).
|
See Implementation Advice.
|
3. Capacity limitations of the implementation. See 1.1.3(3).
|
The complexity of programs that can be processed is limited only by the
total amount of available virtual memory, and disk space for the
generated object files.
|
4. Variations from the standard that are impractical to avoid
given the implementation's execution environment. See 1.1.3(6).
|
There are no variations from the standard.
5. Which code_statements cause external
interactions. See 1.1.3(10).
|
Any code_statement can potentially cause external "cartouche" border="1">
If implementation-defined forms of interrupt handler procedures are
supported, such as protected procedures with parameters, then for each
such form of a handler, a type analogous to Parameterless_Handler
should be specified in a child package of Interrupts, with the
same operations as in the predefined package Interrupts.
|
Followed.
C.4(14): Pre-elaboration Requirements
|
It is recommended that pre-elaborated packages be implemented in such a
way that there should be little or no code executed at run time for the
elaboration of entities not already covered by the Implementation
Requirements.
|
Followed. Executable code is generated in some cases, e.g. loops
to initialize large arrays.
C.5(8): Pragma Discard_Names
|
If the pragma applies to an entity, then the implementation should
reduce the amount of storage used for storing names associated with that
entity.
|
Followed.
C.7.2(30): The Package Task_Attributes
|
Some implementations are targeted to domains in which memory use at run
time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first N
attribute objects, and the heap for the others. In the latter case,
N should be documented.
|
Not followed. This implementation is not targeted to such a domain.
D.3(17): Locking Policies
|
The implementation should use names that end with _Locking for
locking policies defined by the implementation.
|
Followed. A single implementation-defined locking policy is defined,
whose name (Inheritance_Locking) follows this suggestion.
D.4(16): Entry Queuing Policies
|
Names that end with _Queuing should be used
for all implementation-defined queuing policies.
|
Followed. No such implementation-defined queuing policies exist.
D.6(9-10): Preemptive Abort
Even though the abort_statement is included in the list of
potentially blocking operations (see 9.5.1), it is recommended that this
statement be implemented in a way that never requires the task executing
the abort_statement to block.
|
Followed.
|
On a multi-processor, the delay associated with aborting a task on
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
|
Followed.
D.7(21): Tasking Restrictions
|
When feasible, the implementation should take advantage of the specified
restrictions to produce a more efficient implementation.
|
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
of restrictions are specified. See pragma Ravenscar and pragma
Restricted_Run_Time for more details.
D.8(47-49): Monotonic Time
When appropriate, implementations should provide configuration
mechanisms to change the value of Tick.
|
Such configuration mechanisms are not appropriate to this implementation
and are thus not supported.
It is recommended that Calendar.Clock and Real_Time.Clock
be implemented as transformations of the same time base.
|
Followed.
It is recommended that the best time base which exists in
the underlying system be available to the application through
Clock. Best may mean highest accuracy or largest range.
|
Followed.
E.5(28-29): Partition Communication Subsystem
|
Whenever possible, the PCS on the called partition should allow for
multiple tasks to call the RPC-receiver with different messages and
should allow them to block until the corresponding subprogram body
returns.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
The Write operation on a stream of type Params_Stream_Type
should raise Storage_Error if it runs out of space trying to
write the Item into the stream.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
F(7): COBOL Support
If COBOL (respectively, C) is widely supported in the target
environment, implementations supporting the Information Systems Annex
should provide the child package Interfaces.COBOL (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of COBOL (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
F.1(2): Decimal Radix Support
|
Packed decimal should be used as the internal representation for objects
of subtype S when S'Machine_Radix = 10.
|
Not followed. GNAT ignores S'Machine_Radix and always uses binary
representations.
G: Numerics
If Fortran (respectively, C) is widely supported in the target
environment, implementations supporting the Numerics Annex
should provide the child package Interfaces.Fortran (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of Fortran (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
G.1.1(56-58): Complex Types
|
Because the usual mathematical meaning of multiplication of a complex
operand and a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
|
Not followed.
Similarly, because the usual mathematical meaning of addition of a
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
complex addition. In implementations in which the Signed_Zeros
attribute of the component type is True (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
|
Not followed.
Implementations in which Real'Signed_Zeros is True should
attempt to provide a rational treatment of the signs of zero results and
result components. As one example, the result of the Argument
function should have the sign of the imaginary component of the
parameter X when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
of the Compose_From_Polar function should be the same as
(respectively, the opposite of) that of the Argument parameter when that
parameter has a value of zero and the Modulus parameter has a
nonnegative (respectively, negative) value.
|
Followed.
G.1.2(49): Complex Elementary Functions
Implementations in which Complex_Types.Real'Signed_Zeros is
True should attempt to provide a rational treatment of the signs
of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
a parameter component at the origin, or is always positive or always
negative.
|
Followed.
G.2.4(19): Accuracy Requirements
The versions of the forward trigonometric functions without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain. For the same reason, the
version of Log without a Base parameter should not be
implemented by calling the corresponding version with a Base
parameter of Numerics.e.
|
Followed.
G.2.6(15): Complex Arithmetic Accuracy
The version of the Compose_From_Polar function without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain.
|
Followed.
4 Implementation Defined Characteristics
In addition to the implementation dependent pragmas and attributes, and
the implementation advice, there are a number of other features of Ada
95 that are potentially implementation dependent. These are mentioned
throughout the Ada 95 Reference Manual, and are summarized in annex M.
A requirement for conforming Ada compilers is that they provide
documentation describing how the implementation deals with each of these
issues. In this chapter, you will find each point in annex M listed
followed by a description in italic font of how GNAT
handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation
dependent features in your programs if portability to other compilers
and other operating systems is an important consideration. The numbers
in each section below correspond to the paragraph number in the Ada 95
Reference Manual.
|
2. Whether or not each recommendation given in Implementation
Advice is followed. See 1.1.2(37).
|
See Implementation Advice.
|
3. Capacity limitations of the implementation. See 1.1.3(3).
|
The complexity of programs that can be processed is limited only by the
total amount of available virtual memory, and disk space for the
generated object files.
|
4. Variations from the standard that are impractical to avoid
given the implementation's execution environment. See 1.1.3(6).
|
There are no variations from the standard.
5. Which code_statements cause external
interactions. See 1.1.3(10).
|
Any code_statement can potentially cause external "cartouche" border="1">
If implementation-defined forms of interrupt handler procedures are
supported, such as protected procedures with parameters, then for each
such form of a handler, a type analogous to Parameterless_Handler
should be specified in a child package of Interrupts, with the
same operations as in the predefined package Interrupts.
|
Followed.
C.4(14): Pre-elaboration Requirements
|
It is recommended that pre-elaborated packages be implemented in such a
way that there should be little or no code executed at run time for the
elaboration of entities not already covered by the Implementation
Requirements.
|
Followed. Executable code is generated in some cases, e.g. loops
to initialize large arrays.
C.5(8): Pragma Discard_Names
|
If the pragma applies to an entity, then the implementation should
reduce the amount of storage used for storing names associated with that
entity.
|
Followed.
C.7.2(30): The Package Task_Attributes
|
Some implementations are targeted to domains in which memory use at run
time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first N
attribute objects, and the heap for the others. In the latter case,
N should be documented.
|
Not followed. This implementation is not targeted to such a domain.
D.3(17): Locking Policies
|
The implementation should use names that end with _Locking for
locking policies defined by the implementation.
|
Followed. A single implementation-defined locking policy is defined,
whose name (Inheritance_Locking) follows this suggestion.
D.4(16): Entry Queuing Policies
|
Names that end with _Queuing should be used
for all implementation-defined queuing policies.
|
Followed. No such implementation-defined queuing policies exist.
D.6(9-10): Preemptive Abort
Even though the abort_statement is included in the list of
potentially blocking operations (see 9.5.1), it is recommended that this
statement be implemented in a way that never requires the task executing
the abort_statement to block.
|
Followed.
|
On a multi-processor, the delay associated with aborting a task on
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
|
Followed.
D.7(21): Tasking Restrictions
|
When feasible, the implementation should take advantage of the specified
restrictions to produce a more efficient implementation.
|
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
of restrictions are specified. See pragma Ravenscar and pragma
Restricted_Run_Time for more details.
D.8(47-49): Monotonic Time
When appropriate, implementations should provide configuration
mechanisms to change the value of Tick.
|
Such configuration mechanisms are not appropriate to this implementation
and are thus not supported.
It is recommended that Calendar.Clock and Real_Time.Clock
be implemented as transformations of the same time base.
|
Followed.
It is recommended that the best time base which exists in
the underlying system be available to the application through
Clock. Best may mean highest accuracy or largest range.
|
Followed.
E.5(28-29): Partition Communication Subsystem
|
Whenever possible, the PCS on the called partition should allow for
multiple tasks to call the RPC-receiver with different messages and
should allow them to block until the corresponding subprogram body
returns.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
The Write operation on a stream of type Params_Stream_Type
should raise Storage_Error if it runs out of space trying to
write the Item into the stream.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
F(7): COBOL Support
If COBOL (respectively, C) is widely supported in the target
environment, implementations supporting the Information Systems Annex
should provide the child package Interfaces.COBOL (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of COBOL (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
F.1(2): Decimal Radix Support
|
Packed decimal should be used as the internal representation for objects
of subtype S when S'Machine_Radix = 10.
|
Not followed. GNAT ignores S'Machine_Radix and always uses binary
representations.
G: Numerics
If Fortran (respectively, C) is widely supported in the target
environment, implementations supporting the Numerics Annex
should provide the child package Interfaces.Fortran (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of Fortran (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
G.1.1(56-58): Complex Types
|
Because the usual mathematical meaning of multiplication of a complex
operand and a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
|
Not followed.
Similarly, because the usual mathematical meaning of addition of a
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
complex addition. In implementations in which the Signed_Zeros
attribute of the component type is True (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
|
Not followed.
Implementations in which Real'Signed_Zeros is True should
attempt to provide a rational treatment of the signs of zero results and
result components. As one example, the result of the Argument
function should have the sign of the imaginary component of the
parameter X when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
of the Compose_From_Polar function should be the same as
(respectively, the opposite of) that of the Argument parameter when that
parameter has a value of zero and the Modulus parameter has a
nonnegative (respectively, negative) value.
|
Followed.
G.1.2(49): Complex Elementary Functions
Implementations in which Complex_Types.Real'Signed_Zeros is
True should attempt to provide a rational treatment of the signs
of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
a parameter component at the origin, or is always positive or always
negative.
|
Followed.
G.2.4(19): Accuracy Requirements
The versions of the forward trigonometric functions without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain. For the same reason, the
version of Log without a Base parameter should not be
implemented by calling the corresponding version with a Base
parameter of Numerics.e.
|
Followed.
G.2.6(15): Complex Arithmetic Accuracy
The version of the Compose_From_Polar function without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain.
|
Followed.
4 Implementation Defined Characteristics
In addition to the implementation dependent pragmas and attributes, and
the implementation advice, there are a number of other features of Ada
95 that are potentially implementation dependent. These are mentioned
throughout the Ada 95 Reference Manual, and are summarized in annex M.
A requirement for conforming Ada compilers is that they provide
documentation describing how the implementation deals with each of these
issues. In this chapter, you will find each point in annex M listed
followed by a description in italic font of how GNAT
handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation
dependent features in your programs if portability to other compilers
and other operating systems is an important consideration. The numbers
in each section below correspond to the paragraph number in the Ada 95
Reference Manual.
|
2. Whether or not each recommendation given in Implementation
Advice is followed. See 1.1.2(37).
|
See Implementation Advice.
|
3. Capacity limitations of the implementation. See 1.1.3(3).
|
The complexity of programs that can be processed is limited only by the
total amount of available virtual memory, and disk space for the
generated object files.
|
4. Variations from the standard that are impractical to avoid
given the implementation's execution environment. See 1.1.3(6).
|
There are no variations from the standard.
5. Which code_statements cause external
interactions. See 1.1.3(10).
|
Any code_statement can potentially cause external "cartouche" border="1">
If implementation-defined forms of interrupt handler procedures are
supported, such as protected procedures with parameters, then for each
such form of a handler, a type analogous to Parameterless_Handler
should be specified in a child package of Interrupts, with the
same operations as in the predefined package Interrupts.
|
Followed.
C.4(14): Pre-elaboration Requirements
|
It is recommended that pre-elaborated packages be implemented in such a
way that there should be little or no code executed at run time for the
elaboration of entities not already covered by the Implementation
Requirements.
|
Followed. Executable code is generated in some cases, e.g. loops
to initialize large arrays.
C.5(8): Pragma Discard_Names
|
If the pragma applies to an entity, then the implementation should
reduce the amount of storage used for storing names associated with that
entity.
|
Followed.
C.7.2(30): The Package Task_Attributes
|
Some implementations are targeted to domains in which memory use at run
time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first N
attribute objects, and the heap for the others. In the latter case,
N should be documented.
|
Not followed. This implementation is not targeted to such a domain.
D.3(17): Locking Policies
|
The implementation should use names that end with _Locking for
locking policies defined by the implementation.
|
Followed. A single implementation-defined locking policy is defined,
whose name (Inheritance_Locking) follows this suggestion.
D.4(16): Entry Queuing Policies
|
Names that end with _Queuing should be used
for all implementation-defined queuing policies.
|
Followed. No such implementation-defined queuing policies exist.
D.6(9-10): Preemptive Abort
Even though the abort_statement is included in the list of
potentially blocking operations (see 9.5.1), it is recommended that this
statement be implemented in a way that never requires the task executing
the abort_statement to block.
|
Followed.
|
On a multi-processor, the delay associated with aborting a task on
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
|
Followed.
D.7(21): Tasking Restrictions
|
When feasible, the implementation should take advantage of the specified
restrictions to produce a more efficient implementation.
|
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
of restrictions are specified. See pragma Ravenscar and pragma
Restricted_Run_Time for more details.
D.8(47-49): Monotonic Time
When appropriate, implementations should provide configuration
mechanisms to change the value of Tick.
|
Such configuration mechanisms are not appropriate to this implementation
and are thus not supported.
It is recommended that Calendar.Clock and Real_Time.Clock
be implemented as transformations of the same time base.
|
Followed.
It is recommended that the best time base which exists in
the underlying system be available to the application through
Clock. Best may mean highest accuracy or largest range.
|
Followed.
E.5(28-29): Partition Communication Subsystem
|
Whenever possible, the PCS on the called partition should allow for
multiple tasks to call the RPC-receiver with different messages and
should allow them to block until the corresponding subprogram body
returns.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
The Write operation on a stream of type Params_Stream_Type
should raise Storage_Error if it runs out of space trying to
write the Item into the stream.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
F(7): COBOL Support
If COBOL (respectively, C) is widely supported in the target
environment, implementations supporting the Information Systems Annex
should provide the child package Interfaces.COBOL (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of COBOL (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
F.1(2): Decimal Radix Support
|
Packed decimal should be used as the internal representation for objects
of subtype S when S'Machine_Radix = 10.
|
Not followed. GNAT ignores S'Machine_Radix and always uses binary
representations.
G: Numerics
If Fortran (respectively, C) is widely supported in the target
environment, implementations supporting the Numerics Annex
should provide the child package Interfaces.Fortran (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of Fortran (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
G.1.1(56-58): Complex Types
|
Because the usual mathematical meaning of multiplication of a complex
operand and a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
|
Not followed.
Similarly, because the usual mathematical meaning of addition of a
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
complex addition. In implementations in which the Signed_Zeros
attribute of the component type is True (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
|
Not followed.
Implementations in which Real'Signed_Zeros is True should
attempt to provide a rational treatment of the signs of zero results and
result components. As one example, the result of the Argument
function should have the sign of the imaginary component of the
parameter X when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
of the Compose_From_Polar function should be the same as
(respectively, the opposite of) that of the Argument parameter when that
parameter has a value of zero and the Modulus parameter has a
nonnegative (respectively, negative) value.
|
Followed.
G.1.2(49): Complex Elementary Functions
Implementations in which Complex_Types.Real'Signed_Zeros is
True should attempt to provide a rational treatment of the signs
of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
a parameter component at the origin, or is always positive or always
negative.
|
Followed.
G.2.4(19): Accuracy Requirements
The versions of the forward trigonometric functions without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain. For the same reason, the
version of Log without a Base parameter should not be
implemented by calling the corresponding version with a Base
parameter of Numerics.e.
|
Followed.
G.2.6(15): Complex Arithmetic Accuracy
The version of the Compose_From_Polar function without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain.
|
Followed.
4 Implementation Defined Characteristics
In addition to the implementation dependent pragmas and attributes, and
the implementation advice, there are a number of other features of Ada
95 that are potentially implementation dependent. These are mentioned
throughout the Ada 95 Reference Manual, and are summarized in annex M.
A requirement for conforming Ada compilers is that they provide
documentation describing how the implementation deals with each of these
issues. In this chapter, you will find each point in annex M listed
followed by a description in italic font of how GNAT
handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation
dependent features in your programs if portability to other compilers
and other operating systems is an important consideration. The numbers
in each section below correspond to the paragraph number in the Ada 95
Reference Manual.
|
2. Whether or not each recommendation given in Implementation
Advice is followed. See 1.1.2(37).
|
See Implementation Advice.
|
3. Capacity limitations of the implementation. See 1.1.3(3).
|
The complexity of programs that can be processed is limited only by the
total amount of available virtual memory, and disk space for the
generated object files.
|
4. Variations from the standard that are impractical to avoid
given the implementation's execution environment. See 1.1.3(6).
|
There are no variations from the standard.
5. Which code_statements cause external
interactions. See 1.1.3(10).
|
Any code_statement can potentially cause external "cartouche" border="1">
If implementation-defined forms of interrupt handler procedures are
supported, such as protected procedures with parameters, then for each
such form of a handler, a type analogous to Parameterless_Handler
should be specified in a child package of Interrupts, with the
same operations as in the predefined package Interrupts.
|
Followed.
C.4(14): Pre-elaboration Requirements
|
It is recommended that pre-elaborated packages be implemented in such a
way that there should be little or no code executed at run time for the
elaboration of entities not already covered by the Implementation
Requirements.
|
Followed. Executable code is generated in some cases, e.g. loops
to initialize large arrays.
C.5(8): Pragma Discard_Names
|
If the pragma applies to an entity, then the implementation should
reduce the amount of storage used for storing names associated with that
entity.
|
Followed.
C.7.2(30): The Package Task_Attributes
|
Some implementations are targeted to domains in which memory use at run
time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first N
attribute objects, and the heap for the others. In the latter case,
N should be documented.
|
Not followed. This implementation is not targeted to such a domain.
D.3(17): Locking Policies
|
The implementation should use names that end with _Locking for
locking policies defined by the implementation.
|
Followed. A single implementation-defined locking policy is defined,
whose name (Inheritance_Locking) follows this suggestion.
D.4(16): Entry Queuing Policies
|
Names that end with _Queuing should be used
for all implementation-defined queuing policies.
|
Followed. No such implementation-defined queuing policies exist.
D.6(9-10): Preemptive Abort
Even though the abort_statement is included in the list of
potentially blocking operations (see 9.5.1), it is recommended that this
statement be implemented in a way that never requires the task executing
the abort_statement to block.
|
Followed.
|
On a multi-processor, the delay associated with aborting a task on
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
|
Followed.
D.7(21): Tasking Restrictions
|
When feasible, the implementation should take advantage of the specified
restrictions to produce a more efficient implementation.
|
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
of restrictions are specified. See pragma Ravenscar and pragma
Restricted_Run_Time for more details.
D.8(47-49): Monotonic Time
When appropriate, implementations should provide configuration
mechanisms to change the value of Tick.
|
Such configuration mechanisms are not appropriate to this implementation
and are thus not supported.
It is recommended that Calendar.Clock and Real_Time.Clock
be implemented as transformations of the same time base.
|
Followed.
It is recommended that the best time base which exists in
the underlying system be available to the application through
Clock. Best may mean highest accuracy or largest range.
|
Followed.
E.5(28-29): Partition Communication Subsystem
|
Whenever possible, the PCS on the called partition should allow for
multiple tasks to call the RPC-receiver with different messages and
should allow them to block until the corresponding subprogram body
returns.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
The Write operation on a stream of type Params_Stream_Type
should raise Storage_Error if it runs out of space trying to
write the Item into the stream.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
F(7): COBOL Support
If COBOL (respectively, C) is widely supported in the target
environment, implementations supporting the Information Systems Annex
should provide the child package Interfaces.COBOL (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of COBOL (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
F.1(2): Decimal Radix Support
|
Packed decimal should be used as the internal representation for objects
of subtype S when S'Machine_Radix = 10.
|
Not followed. GNAT ignores S'Machine_Radix and always uses binary
representations.
G: Numerics
If Fortran (respectively, C) is widely supported in the target
environment, implementations supporting the Numerics Annex
should provide the child package Interfaces.Fortran (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of Fortran (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
G.1.1(56-58): Complex Types
|
Because the usual mathematical meaning of multiplication of a complex
operand and a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
|
Not followed.
Similarly, because the usual mathematical meaning of addition of a
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
complex addition. In implementations in which the Signed_Zeros
attribute of the component type is True (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
|
Not followed.
Implementations in which Real'Signed_Zeros is True should
attempt to provide a rational treatment of the signs of zero results and
result components. As one example, the result of the Argument
function should have the sign of the imaginary component of the
parameter X when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
of the Compose_From_Polar function should be the same as
(respectively, the opposite of) that of the Argument parameter when that
parameter has a value of zero and the Modulus parameter has a
nonnegative (respectively, negative) value.
|
Followed.
G.1.2(49): Complex Elementary Functions
Implementations in which Complex_Types.Real'Signed_Zeros is
True should attempt to provide a rational treatment of the signs
of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
a parameter component at the origin, or is always positive or always
negative.
|
Followed.
G.2.4(19): Accuracy Requirements
The versions of the forward trigonometric functions without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain. For the same reason, the
version of Log without a Base parameter should not be
implemented by calling the corresponding version with a Base
parameter of Numerics.e.
|
Followed.
G.2.6(15): Complex Arithmetic Accuracy
The version of the Compose_From_Polar function without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain.
|
Followed.
4 Implementation Defined Characteristics
In addition to the implementation dependent pragmas and attributes, and
the implementation advice, there are a number of other features of Ada
95 that are potentially implementation dependent. These are mentioned
throughout the Ada 95 Reference Manual, and are summarized in annex M.
A requirement for conforming Ada compilers is that they provide
documentation describing how the implementation deals with each of these
issues. In this chapter, you will find each point in annex M listed
followed by a description in italic font of how GNAT
handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation
dependent features in your programs if portability to other compilers
and other operating systems is an important consideration. The numbers
in each section below correspond to the paragraph number in the Ada 95
Reference Manual.
|
2. Whether or not each recommendation given in Implementation
Advice is followed. See 1.1.2(37).
|
See Implementation Advice.
|
3. Capacity limitations of the implementation. See 1.1.3(3).
|
The complexity of programs that can be processed is limited only by the
total amount of available virtual memory, and disk space for the
generated object files.
|
4. Variations from the standard that are impractical to avoid
given the implementation's execution environment. See 1.1.3(6).
|
There are no variations from the standard.
5. Which code_statements cause external
interactions. See 1.1.3(10).
|
Any code_statement can potentially cause external "cartouche" border="1">
If implementation-defined forms of interrupt handler procedures are
supported, such as protected procedures with parameters, then for each
such form of a handler, a type analogous to Parameterless_Handler
should be specified in a child package of Interrupts, with the
same operations as in the predefined package Interrupts.
|
Followed.
C.4(14): Pre-elaboration Requirements
|
It is recommended that pre-elaborated packages be implemented in such a
way that there should be little or no code executed at run time for the
elaboration of entities not already covered by the Implementation
Requirements.
|
Followed. Executable code is generated in some cases, e.g. loops
to initialize large arrays.
C.5(8): Pragma Discard_Names
|
If the pragma applies to an entity, then the implementation should
reduce the amount of storage used for storing names associated with that
entity.
|
Followed.
C.7.2(30): The Package Task_Attributes
|
Some implementations are targeted to domains in which memory use at run
time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first N
attribute objects, and the heap for the others. In the latter case,
N should be documented.
|
Not followed. This implementation is not targeted to such a domain.
D.3(17): Locking Policies
|
The implementation should use names that end with _Locking for
locking policies defined by the implementation.
|
Followed. A single implementation-defined locking policy is defined,
whose name (Inheritance_Locking) follows this suggestion.
D.4(16): Entry Queuing Policies
|
Names that end with _Queuing should be used
for all implementation-defined queuing policies.
|
Followed. No such implementation-defined queuing policies exist.
D.6(9-10): Preemptive Abort
Even though the abort_statement is included in the list of
potentially blocking operations (see 9.5.1), it is recommended that this
statement be implemented in a way that never requires the task executing
the abort_statement to block.
|
Followed.
|
On a multi-processor, the delay associated with aborting a task on
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
|
Followed.
D.7(21): Tasking Restrictions
|
When feasible, the implementation should take advantage of the specified
restrictions to produce a more efficient implementation.
|
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
of restrictions are specified. See pragma Ravenscar and pragma
Restricted_Run_Time for more details.
D.8(47-49): Monotonic Time
When appropriate, implementations should provide configuration
mechanisms to change the value of Tick.
|
Such configuration mechanisms are not appropriate to this implementation
and are thus not supported.
It is recommended that Calendar.Clock and Real_Time.Clock
be implemented as transformations of the same time base.
|
Followed.
It is recommended that the best time base which exists in
the underlying system be available to the application through
Clock. Best may mean highest accuracy or largest range.
|
Followed.
E.5(28-29): Partition Communication Subsystem
|
Whenever possible, the PCS on the called partition should allow for
multiple tasks to call the RPC-receiver with different messages and
should allow them to block until the corresponding subprogram body
returns.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
The Write operation on a stream of type Params_Stream_Type
should raise Storage_Error if it runs out of space trying to
write the Item into the stream.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
F(7): COBOL Support
If COBOL (respectively, C) is widely supported in the target
environment, implementations supporting the Information Systems Annex
should provide the child package Interfaces.COBOL (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of COBOL (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
F.1(2): Decimal Radix Support
|
Packed decimal should be used as the internal representation for objects
of subtype S when S'Machine_Radix = 10.
|
Not followed. GNAT ignores S'Machine_Radix and always uses binary
representations.
G: Numerics
If Fortran (respectively, C) is widely supported in the target
environment, implementations supporting the Numerics Annex
should provide the child package Interfaces.Fortran (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of Fortran (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
G.1.1(56-58): Complex Types
|
Because the usual mathematical meaning of multiplication of a complex
operand and a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
|
Not followed.
Similarly, because the usual mathematical meaning of addition of a
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
complex addition. In implementations in which the Signed_Zeros
attribute of the component type is True (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
|
Not followed.
Implementations in which Real'Signed_Zeros is True should
attempt to provide a rational treatment of the signs of zero results and
result components. As one example, the result of the Argument
function should have the sign of the imaginary component of the
parameter X when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
of the Compose_From_Polar function should be the same as
(respectively, the opposite of) that of the Argument parameter when that
parameter has a value of zero and the Modulus parameter has a
nonnegative (respectively, negative) value.
|
Followed.
G.1.2(49): Complex Elementary Functions
Implementations in which Complex_Types.Real'Signed_Zeros is
True should attempt to provide a rational treatment of the signs
of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
a parameter component at the origin, or is always positive or always
negative.
|
Followed.
G.2.4(19): Accuracy Requirements
The versions of the forward trigonometric functions without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain. For the same reason, the
version of Log without a Base parameter should not be
implemented by calling the corresponding version with a Base
parameter of Numerics.e.
|
Followed.
G.2.6(15): Complex Arithmetic Accuracy
The version of the Compose_From_Polar function without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain.
|
Followed.
4 Implementation Defined Characteristics
In addition to the implementation dependent pragmas and attributes, and
the implementation advice, there are a number of other features of Ada
95 that are potentially implementation dependent. These are mentioned
throughout the Ada 95 Reference Manual, and are summarized in annex M.
A requirement for conforming Ada compilers is that they provide
documentation describing how the implementation deals with each of these
issues. In this chapter, you will find each point in annex M listed
followed by a description in italic font of how GNAT
handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation
dependent features in your programs if portability to other compilers
and other operating systems is an important consideration. The numbers
in each section below correspond to the paragraph number in the Ada 95
Reference Manual.
|
2. Whether or not each recommendation given in Implementation
Advice is followed. See 1.1.2(37).
|
See Implementation Advice.
|
3. Capacity limitations of the implementation. See 1.1.3(3).
|
The complexity of programs that can be processed is limited only by the
total amount of available virtual memory, and disk space for the
generated object files.
|
4. Variations from the standard that are impractical to avoid
given the implementation's execution environment. See 1.1.3(6).
|
There are no variations from the standard.
5. Which code_statements cause external
interactions. See 1.1.3(10).
|
Any code_statement can potentially cause external "cartouche" border="1">
If implementation-defined forms of interrupt handler procedures are
supported, such as protected procedures with parameters, then for each
such form of a handler, a type analogous to Parameterless_Handler
should be specified in a child package of Interrupts, with the
same operations as in the predefined package Interrupts.
|
Followed.
C.4(14): Pre-elaboration Requirements
|
It is recommended that pre-elaborated packages be implemented in such a
way that there should be little or no code executed at run time for the
elaboration of entities not already covered by the Implementation
Requirements.
|
Followed. Executable code is generated in some cases, e.g. loops
to initialize large arrays.
C.5(8): Pragma Discard_Names
|
If the pragma applies to an entity, then the implementation should
reduce the amount of storage used for storing names associated with that
entity.
|
Followed.
C.7.2(30): The Package Task_Attributes
|
Some implementations are targeted to domains in which memory use at run
time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first N
attribute objects, and the heap for the others. In the latter case,
N should be documented.
|
Not followed. This implementation is not targeted to such a domain.
D.3(17): Locking Policies
|
The implementation should use names that end with _Locking for
locking policies defined by the implementation.
|
Followed. A single implementation-defined locking policy is defined,
whose name (Inheritance_Locking) follows this suggestion.
D.4(16): Entry Queuing Policies
|
Names that end with _Queuing should be used
for all implementation-defined queuing policies.
|
Followed. No such implementation-defined queuing policies exist.
D.6(9-10): Preemptive Abort
Even though the abort_statement is included in the list of
potentially blocking operations (see 9.5.1), it is recommended that this
statement be implemented in a way that never requires the task executing
the abort_statement to block.
|
Followed.
|
On a multi-processor, the delay associated with aborting a task on
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
|
Followed.
D.7(21): Tasking Restrictions
|
When feasible, the implementation should take advantage of the specified
restrictions to produce a more efficient implementation.
|
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
of restrictions are specified. See pragma Ravenscar and pragma
Restricted_Run_Time for more details.
D.8(47-49): Monotonic Time
When appropriate, implementations should provide configuration
mechanisms to change the value of Tick.
|
Such configuration mechanisms are not appropriate to this implementation
and are thus not supported.
It is recommended that Calendar.Clock and Real_Time.Clock
be implemented as transformations of the same time base.
|
Followed.
It is recommended that the best time base which exists in
the underlying system be available to the application through
Clock. Best may mean highest accuracy or largest range.
|
Followed.
E.5(28-29): Partition Communication Subsystem
|
Whenever possible, the PCS on the called partition should allow for
multiple tasks to call the RPC-receiver with different messages and
should allow them to block until the corresponding subprogram body
returns.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
The Write operation on a stream of type Params_Stream_Type
should raise Storage_Error if it runs out of space trying to
write the Item into the stream.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
F(7): COBOL Support
If COBOL (respectively, C) is widely supported in the target
environment, implementations supporting the Information Systems Annex
should provide the child package Interfaces.COBOL (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of COBOL (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
F.1(2): Decimal Radix Support
|
Packed decimal should be used as the internal representation for objects
of subtype S when S'Machine_Radix = 10.
|
Not followed. GNAT ignores S'Machine_Radix and always uses binary
representations.
G: Numerics
If Fortran (respectively, C) is widely supported in the target
environment, implementations supporting the Numerics Annex
should provide the child package Interfaces.Fortran (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of Fortran (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
G.1.1(56-58): Complex Types
|
Because the usual mathematical meaning of multiplication of a complex
operand and a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
|
Not followed.
Similarly, because the usual mathematical meaning of addition of a
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
complex addition. In implementations in which the Signed_Zeros
attribute of the component type is True (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
|
Not followed.
Implementations in which Real'Signed_Zeros is True should
attempt to provide a rational treatment of the signs of zero results and
result components. As one example, the result of the Argument
function should have the sign of the imaginary component of the
parameter X when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
of the Compose_From_Polar function should be the same as
(respectively, the opposite of) that of the Argument parameter when that
parameter has a value of zero and the Modulus parameter has a
nonnegative (respectively, negative) value.
|
Followed.
G.1.2(49): Complex Elementary Functions
Implementations in which Complex_Types.Real'Signed_Zeros is
True should attempt to provide a rational treatment of the signs
of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
a parameter component at the origin, or is always positive or always
negative.
|
Followed.
G.2.4(19): Accuracy Requirements
The versions of the forward trigonometric functions without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain. For the same reason, the
version of Log without a Base parameter should not be
implemented by calling the corresponding version with a Base
parameter of Numerics.e.
|
Followed.
G.2.6(15): Complex Arithmetic Accuracy
The version of the Compose_From_Polar function without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain.
|
Followed.
4 Implementation Defined Characteristics
In addition to the implementation dependent pragmas and attributes, and
the implementation advice, there are a number of other features of Ada
95 that are potentially implementation dependent. These are mentioned
throughout the Ada 95 Reference Manual, and are summarized in annex M.
A requirement for conforming Ada compilers is that they provide
documentation describing how the implementation deals with each of these
issues. In this chapter, you will find each point in annex M listed
followed by a description in italic font of how GNAT
handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation
dependent features in your programs if portability to other compilers
and other operating systems is an important consideration. The numbers
in each section below correspond to the paragraph number in the Ada 95
Reference Manual.
|
2. Whether or not each recommendation given in Implementation
Advice is followed. See 1.1.2(37).
|
See Implementation Advice.
|
3. Capacity limitations of the implementation. See 1.1.3(3).
|
The complexity of programs that can be processed is limited only by the
total amount of available virtual memory, and disk space for the
generated object files.
|
4. Variations from the standard that are impractical to avoid
given the implementation's execution environment. See 1.1.3(6).
|
There are no variations from the standard.
5. Which code_statements cause external
interactions. See 1.1.3(10).
|
Any code_statement can potentially cause external "cartouche" border="1">
If implementation-defined forms of interrupt handler procedures are
supported, such as protected procedures with parameters, then for each
such form of a handler, a type analogous to Parameterless_Handler
should be specified in a child package of Interrupts, with the
same operations as in the predefined package Interrupts.
|
Followed.
C.4(14): Pre-elaboration Requirements
|
It is recommended that pre-elaborated packages be implemented in such a
way that there should be little or no code executed at run time for the
elaboration of entities not already covered by the Implementation
Requirements.
|
Followed. Executable code is generated in some cases, e.g. loops
to initialize large arrays.
C.5(8): Pragma Discard_Names
|
If the pragma applies to an entity, then the implementation should
reduce the amount of storage used for storing names associated with that
entity.
|
Followed.
C.7.2(30): The Package Task_Attributes
|
Some implementations are targeted to domains in which memory use at run
time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first N
attribute objects, and the heap for the others. In the latter case,
N should be documented.
|
Not followed. This implementation is not targeted to such a domain.
D.3(17): Locking Policies
|
The implementation should use names that end with _Locking for
locking policies defined by the implementation.
|
Followed. A single implementation-defined locking policy is defined,
whose name (Inheritance_Locking) follows this suggestion.
D.4(16): Entry Queuing Policies
|
Names that end with _Queuing should be used
for all implementation-defined queuing policies.
|
Followed. No such implementation-defined queuing policies exist.
D.6(9-10): Preemptive Abort
Even though the abort_statement is included in the list of
potentially blocking operations (see 9.5.1), it is recommended that this
statement be implemented in a way that never requires the task executing
the abort_statement to block.
|
Followed.
|
On a multi-processor, the delay associated with aborting a task on
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
|
Followed.
D.7(21): Tasking Restrictions
|
When feasible, the implementation should take advantage of the specified
restrictions to produce a more efficient implementation.
|
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
of restrictions are specified. See pragma Ravenscar and pragma
Restricted_Run_Time for more details.
D.8(47-49): Monotonic Time
When appropriate, implementations should provide configuration
mechanisms to change the value of Tick.
|
Such configuration mechanisms are not appropriate to this implementation
and are thus not supported.
It is recommended that Calendar.Clock and Real_Time.Clock
be implemented as transformations of the same time base.
|
Followed.
It is recommended that the best time base which exists in
the underlying system be available to the application through
Clock. Best may mean highest accuracy or largest range.
|
Followed.
E.5(28-29): Partition Communication Subsystem
|
Whenever possible, the PCS on the called partition should allow for
multiple tasks to call the RPC-receiver with different messages and
should allow them to block until the corresponding subprogram body
returns.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
The Write operation on a stream of type Params_Stream_Type
should raise Storage_Error if it runs out of space trying to
write the Item into the stream.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
F(7): COBOL Support
If COBOL (respectively, C) is widely supported in the target
environment, implementations supporting the Information Systems Annex
should provide the child package Interfaces.COBOL (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of COBOL (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
F.1(2): Decimal Radix Support
|
Packed decimal should be used as the internal representation for objects
of subtype S when S'Machine_Radix = 10.
|
Not followed. GNAT ignores S'Machine_Radix and always uses binary
representations.
G: Numerics
If Fortran (respectively, C) is widely supported in the target
environment, implementations supporting the Numerics Annex
should provide the child package Interfaces.Fortran (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of Fortran (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
G.1.1(56-58): Complex Types
|
Because the usual mathematical meaning of multiplication of a complex
operand and a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
|
Not followed.
Similarly, because the usual mathematical meaning of addition of a
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
complex addition. In implementations in which the Signed_Zeros
attribute of the component type is True (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
|
Not followed.
Implementations in which Real'Signed_Zeros is True should
attempt to provide a rational treatment of the signs of zero results and
result components. As one example, the result of the Argument
function should have the sign of the imaginary component of the
parameter X when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
of the Compose_From_Polar function should be the same as
(respectively, the opposite of) that of the Argument parameter when that
parameter has a value of zero and the Modulus parameter has a
nonnegative (respectively, negative) value.
|
Followed.
G.1.2(49): Complex Elementary Functions
Implementations in which Complex_Types.Real'Signed_Zeros is
True should attempt to provide a rational treatment of the signs
of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
a parameter component at the origin, or is always positive or always
negative.
|
Followed.
G.2.4(19): Accuracy Requirements
The versions of the forward trigonometric functions without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain. For the same reason, the
version of Log without a Base parameter should not be
implemented by calling the corresponding version with a Base
parameter of Numerics.e.
|
Followed.
G.2.6(15): Complex Arithmetic Accuracy
The version of the Compose_From_Polar function without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain.
|
Followed.
4 Implementation Defined Characteristics
In addition to the implementation dependent pragmas and attributes, and
the implementation advice, there are a number of other features of Ada
95 that are potentially implementation dependent. These are mentioned
throughout the Ada 95 Reference Manual, and are summarized in annex M.
A requirement for conforming Ada compilers is that they provide
documentation describing how the implementation deals with each of these
issues. In this chapter, you will find each point in annex M listed
followed by a description in italic font of how GNAT
handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation
dependent features in your programs if portability to other compilers
and other operating systems is an important consideration. The numbers
in each section below correspond to the paragraph number in the Ada 95
Reference Manual.
|
2. Whether or not each recommendation given in Implementation
Advice is followed. See 1.1.2(37).
|
See Implementation Advice.
|
3. Capacity limitations of the implementation. See 1.1.3(3).
|
The complexity of programs that can be processed is limited only by the
total amount of available virtual memory, and disk space for the
generated object files.
|
4. Variations from the standard that are impractical to avoid
given the implementation's execution environment. See 1.1.3(6).
|
There are no variations from the standard.
5. Which code_statements cause external
interactions. See 1.1.3(10).
|
Any code_statement can potentially cause external "cartouche" border="1">
If implementation-defined forms of interrupt handler procedures are
supported, such as protected procedures with parameters, then for each
such form of a handler, a type analogous to Parameterless_Handler
should be specified in a child package of Interrupts, with the
same operations as in the predefined package Interrupts.
|
Followed.
C.4(14): Pre-elaboration Requirements
|
It is recommended that pre-elaborated packages be implemented in such a
way that there should be little or no code executed at run time for the
elaboration of entities not already covered by the Implementation
Requirements.
|
Followed. Executable code is generated in some cases, e.g. loops
to initialize large arrays.
C.5(8): Pragma Discard_Names
|
If the pragma applies to an entity, then the implementation should
reduce the amount of storage used for storing names associated with that
entity.
|
Followed.
C.7.2(30): The Package Task_Attributes
|
Some implementations are targeted to domains in which memory use at run
time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first N
attribute objects, and the heap for the others. In the latter case,
N should be documented.
|
Not followed. This implementation is not targeted to such a domain.
D.3(17): Locking Policies
|
The implementation should use names that end with _Locking for
locking policies defined by the implementation.
|
Followed. A single implementation-defined locking policy is defined,
whose name (Inheritance_Locking) follows this suggestion.
D.4(16): Entry Queuing Policies
|
Names that end with _Queuing should be used
for all implementation-defined queuing policies.
|
Followed. No such implementation-defined queuing policies exist.
D.6(9-10): Preemptive Abort
Even though the abort_statement is included in the list of
potentially blocking operations (see 9.5.1), it is recommended that this
statement be implemented in a way that never requires the task executing
the abort_statement to block.
|
Followed.
|
On a multi-processor, the delay associated with aborting a task on
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
|
Followed.
D.7(21): Tasking Restrictions
|
When feasible, the implementation should take advantage of the specified
restrictions to produce a more efficient implementation.
|
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
of restrictions are specified. See pragma Ravenscar and pragma
Restricted_Run_Time for more details.
D.8(47-49): Monotonic Time
When appropriate, implementations should provide configuration
mechanisms to change the value of Tick.
|
Such configuration mechanisms are not appropriate to this implementation
and are thus not supported.
It is recommended that Calendar.Clock and Real_Time.Clock
be implemented as transformations of the same time base.
|
Followed.
It is recommended that the best time base which exists in
the underlying system be available to the application through
Clock. Best may mean highest accuracy or largest range.
|
Followed.
E.5(28-29): Partition Communication Subsystem
|
Whenever possible, the PCS on the called partition should allow for
multiple tasks to call the RPC-receiver with different messages and
should allow them to block until the corresponding subprogram body
returns.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
The Write operation on a stream of type Params_Stream_Type
should raise Storage_Error if it runs out of space trying to
write the Item into the stream.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
F(7): COBOL Support
If COBOL (respectively, C) is widely supported in the target
environment, implementations supporting the Information Systems Annex
should provide the child package Interfaces.COBOL (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of COBOL (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
F.1(2): Decimal Radix Support
|
Packed decimal should be used as the internal representation for objects
of subtype S when S'Machine_Radix = 10.
|
Not followed. GNAT ignores S'Machine_Radix and always uses binary
representations.
G: Numerics
If Fortran (respectively, C) is widely supported in the target
environment, implementations supporting the Numerics Annex
should provide the child package Interfaces.Fortran (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of Fortran (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
G.1.1(56-58): Complex Types
|
Because the usual mathematical meaning of multiplication of a complex
operand and a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
|
Not followed.
Similarly, because the usual mathematical meaning of addition of a
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
complex addition. In implementations in which the Signed_Zeros
attribute of the component type is True (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
|
Not followed.
Implementations in which Real'Signed_Zeros is True should
attempt to provide a rational treatment of the signs of zero results and
result components. As one example, the result of the Argument
function should have the sign of the imaginary component of the
parameter X when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
of the Compose_From_Polar function should be the same as
(respectively, the opposite of) that of the Argument parameter when that
parameter has a value of zero and the Modulus parameter has a
nonnegative (respectively, negative) value.
|
Followed.
G.1.2(49): Complex Elementary Functions
Implementations in which Complex_Types.Real'Signed_Zeros is
True should attempt to provide a rational treatment of the signs
of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
a parameter component at the origin, or is always positive or always
negative.
|
Followed.
G.2.4(19): Accuracy Requirements
The versions of the forward trigonometric functions without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain. For the same reason, the
version of Log without a Base parameter should not be
implemented by calling the corresponding version with a Base
parameter of Numerics.e.
|
Followed.
G.2.6(15): Complex Arithmetic Accuracy
The version of the Compose_From_Polar function without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain.
|
Followed.
4 Implementation Defined Characteristics
In addition to the implementation dependent pragmas and attributes, and
the implementation advice, there are a number of other features of Ada
95 that are potentially implementation dependent. These are mentioned
throughout the Ada 95 Reference Manual, and are summarized in annex M.
A requirement for conforming Ada compilers is that they provide
documentation describing how the implementation deals with each of these
issues. In this chapter, you will find each point in annex M listed
followed by a description in italic font of how GNAT
handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation
dependent features in your programs if portability to other compilers
and other operating systems is an important consideration. The numbers
in each section below correspond to the paragraph number in the Ada 95
Reference Manual.
|
2. Whether or not each recommendation given in Implementation
Advice is followed. See 1.1.2(37).
|
See Implementation Advice.
|
3. Capacity limitations of the implementation. See 1.1.3(3).
|
The complexity of programs that can be processed is limited only by the
total amount of available virtual memory, and disk space for the
generated object files.
|
4. Variations from the standard that are impractical to avoid
given the implementation's execution environment. See 1.1.3(6).
|
There are no variations from the standard.
5. Which code_statements cause external
interactions. See 1.1.3(10).
|
Any code_statement can potentially cause external "cartouche" border="1">
If implementation-defined forms of interrupt handler procedures are
supported, such as protected procedures with parameters, then for each
such form of a handler, a type analogous to Parameterless_Handler
should be specified in a child package of Interrupts, with the
same operations as in the predefined package Interrupts.
|
Followed.
C.4(14): Pre-elaboration Requirements
|
It is recommended that pre-elaborated packages be implemented in such a
way that there should be little or no code executed at run time for the
elaboration of entities not already covered by the Implementation
Requirements.
|
Followed. Executable code is generated in some cases, e.g. loops
to initialize large arrays.
C.5(8): Pragma Discard_Names
|
If the pragma applies to an entity, then the implementation should
reduce the amount of storage used for storing names associated with that
entity.
|
Followed.
C.7.2(30): The Package Task_Attributes
|
Some implementations are targeted to domains in which memory use at run
time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first N
attribute objects, and the heap for the others. In the latter case,
N should be documented.
|
Not followed. This implementation is not targeted to such a domain.
D.3(17): Locking Policies
|
The implementation should use names that end with _Locking for
locking policies defined by the implementation.
|
Followed. A single implementation-defined locking policy is defined,
whose name (Inheritance_Locking) follows this suggestion.
D.4(16): Entry Queuing Policies
|
Names that end with _Queuing should be used
for all implementation-defined queuing policies.
|
Followed. No such implementation-defined queuing policies exist.
D.6(9-10): Preemptive Abort
Even though the abort_statement is included in the list of
potentially blocking operations (see 9.5.1), it is recommended that this
statement be implemented in a way that never requires the task executing
the abort_statement to block.
|
Followed.
|
On a multi-processor, the delay associated with aborting a task on
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
|
Followed.
D.7(21): Tasking Restrictions
|
When feasible, the implementation should take advantage of the specified
restrictions to produce a more efficient implementation.
|
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
of restrictions are specified. See pragma Ravenscar and pragma
Restricted_Run_Time for more details.
D.8(47-49): Monotonic Time
When appropriate, implementations should provide configuration
mechanisms to change the value of Tick.
|
Such configuration mechanisms are not appropriate to this implementation
and are thus not supported.
It is recommended that Calendar.Clock and Real_Time.Clock
be implemented as transformations of the same time base.
|
Followed.
It is recommended that the best time base which exists in
the underlying system be available to the application through
Clock. Best may mean highest accuracy or largest range.
|
Followed.
E.5(28-29): Partition Communication Subsystem
|
Whenever possible, the PCS on the called partition should allow for
multiple tasks to call the RPC-receiver with different messages and
should allow them to block until the corresponding subprogram body
returns.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
The Write operation on a stream of type Params_Stream_Type
should raise Storage_Error if it runs out of space trying to
write the Item into the stream.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
F(7): COBOL Support
If COBOL (respectively, C) is widely supported in the target
environment, implementations supporting the Information Systems Annex
should provide the child package Interfaces.COBOL (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of COBOL (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
F.1(2): Decimal Radix Support
|
Packed decimal should be used as the internal representation for objects
of subtype S when S'Machine_Radix = 10.
|
Not followed. GNAT ignores S'Machine_Radix and always uses binary
representations.
G: Numerics
If Fortran (respectively, C) is widely supported in the target
environment, implementations supporting the Numerics Annex
should provide the child package Interfaces.Fortran (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of Fortran (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
G.1.1(56-58): Complex Types
|
Because the usual mathematical meaning of multiplication of a complex
operand and a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
|
Not followed.
Similarly, because the usual mathematical meaning of addition of a
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
complex addition. In implementations in which the Signed_Zeros
attribute of the component type is True (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
|
Not followed.
Implementations in which Real'Signed_Zeros is True should
attempt to provide a rational treatment of the signs of zero results and
result components. As one example, the result of the Argument
function should have the sign of the imaginary component of the
parameter X when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
of the Compose_From_Polar function should be the same as
(respectively, the opposite of) that of the Argument parameter when that
parameter has a value of zero and the Modulus parameter has a
nonnegative (respectively, negative) value.
|
Followed.
G.1.2(49): Complex Elementary Functions
Implementations in which Complex_Types.Real'Signed_Zeros is
True should attempt to provide a rational treatment of the signs
of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
a parameter component at the origin, or is always positive or always
negative.
|
Followed.
G.2.4(19): Accuracy Requirements
The versions of the forward trigonometric functions without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain. For the same reason, the
version of Log without a Base parameter should not be
implemented by calling the corresponding version with a Base
parameter of Numerics.e.
|
Followed.
G.2.6(15): Complex Arithmetic Accuracy
The version of the Compose_From_Polar function without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain.
|
Followed.
4 Implementation Defined Characteristics
In addition to the implementation dependent pragmas and attributes, and
the implementation advice, there are a number of other features of Ada
95 that are potentially implementation dependent. These are mentioned
throughout the Ada 95 Reference Manual, and are summarized in annex M.
A requirement for conforming Ada compilers is that they provide
documentation describing how the implementation deals with each of these
issues. In this chapter, you will find each point in annex M listed
followed by a description in italic font of how GNAT
handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation
dependent features in your programs if portability to other compilers
and other operating systems is an important consideration. The numbers
in each section below correspond to the paragraph number in the Ada 95
Reference Manual.
|
2. Whether or not each recommendation given in Implementation
Advice is followed. See 1.1.2(37).
|
See Implementation Advice.
|
3. Capacity limitations of the implementation. See 1.1.3(3).
|
The complexity of programs that can be processed is limited only by the
total amount of available virtual memory, and disk space for the
generated object files.
|
4. Variations from the standard that are impractical to avoid
given the implementation's execution environment. See 1.1.3(6).
|
There are no variations from the standard.
5. Which code_statements cause external
interactions. See 1.1.3(10).
|
Any code_statement can potentially cause external "cartouche" border="1">
If implementation-defined forms of interrupt handler procedures are
supported, such as protected procedures with parameters, then for each
such form of a handler, a type analogous to Parameterless_Handler
should be specified in a child package of Interrupts, with the
same operations as in the predefined package Interrupts.
|
Followed.
C.4(14): Pre-elaboration Requirements
|
It is recommended that pre-elaborated packages be implemented in such a
way that there should be little or no code executed at run time for the
elaboration of entities not already covered by the Implementation
Requirements.
|
Followed. Executable code is generated in some cases, e.g. loops
to initialize large arrays.
C.5(8): Pragma Discard_Names
|
If the pragma applies to an entity, then the implementation should
reduce the amount of storage used for storing names associated with that
entity.
|
Followed.
C.7.2(30): The Package Task_Attributes
|
Some implementations are targeted to domains in which memory use at run
time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first N
attribute objects, and the heap for the others. In the latter case,
N should be documented.
|
Not followed. This implementation is not targeted to such a domain.
D.3(17): Locking Policies
|
The implementation should use names that end with _Locking for
locking policies defined by the implementation.
|
Followed. A single implementation-defined locking policy is defined,
whose name (Inheritance_Locking) follows this suggestion.
D.4(16): Entry Queuing Policies
|
Names that end with _Queuing should be used
for all implementation-defined queuing policies.
|
Followed. No such implementation-defined queuing policies exist.
D.6(9-10): Preemptive Abort
Even though the abort_statement is included in the list of
potentially blocking operations (see 9.5.1), it is recommended that this
statement be implemented in a way that never requires the task executing
the abort_statement to block.
|
Followed.
|
On a multi-processor, the delay associated with aborting a task on
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
|
Followed.
D.7(21): Tasking Restrictions
|
When feasible, the implementation should take advantage of the specified
restrictions to produce a more efficient implementation.
|
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
of restrictions are specified. See pragma Ravenscar and pragma
Restricted_Run_Time for more details.
D.8(47-49): Monotonic Time
When appropriate, implementations should provide configuration
mechanisms to change the value of Tick.
|
Such configuration mechanisms are not appropriate to this implementation
and are thus not supported.
It is recommended that Calendar.Clock and Real_Time.Clock
be implemented as transformations of the same time base.
|
Followed.
It is recommended that the best time base which exists in
the underlying system be available to the application through
Clock. Best may mean highest accuracy or largest range.
|
Followed.
E.5(28-29): Partition Communication Subsystem
|
Whenever possible, the PCS on the called partition should allow for
multiple tasks to call the RPC-receiver with different messages and
should allow them to block until the corresponding subprogram body
returns.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
The Write operation on a stream of type Params_Stream_Type
should raise Storage_Error if it runs out of space trying to
write the Item into the stream.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
F(7): COBOL Support
If COBOL (respectively, C) is widely supported in the target
environment, implementations supporting the Information Systems Annex
should provide the child package Interfaces.COBOL (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of COBOL (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
F.1(2): Decimal Radix Support
|
Packed decimal should be used as the internal representation for objects
of subtype S when S'Machine_Radix = 10.
|
Not followed. GNAT ignores S'Machine_Radix and always uses binary
representations.
G: Numerics
If Fortran (respectively, C) is widely supported in the target
environment, implementations supporting the Numerics Annex
should provide the child package Interfaces.Fortran (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of Fortran (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
G.1.1(56-58): Complex Types
|
Because the usual mathematical meaning of multiplication of a complex
operand and a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
|
Not followed.
Similarly, because the usual mathematical meaning of addition of a
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
complex addition. In implementations in which the Signed_Zeros
attribute of the component type is True (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
|
Not followed.
Implementations in which Real'Signed_Zeros is True should
attempt to provide a rational treatment of the signs of zero results and
result components. As one example, the result of the Argument
function should have the sign of the imaginary component of the
parameter X when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
of the Compose_From_Polar function should be the same as
(respectively, the opposite of) that of the Argument parameter when that
parameter has a value of zero and the Modulus parameter has a
nonnegative (respectively, negative) value.
|
Followed.
G.1.2(49): Complex Elementary Functions
Implementations in which Complex_Types.Real'Signed_Zeros is
True should attempt to provide a rational treatment of the signs
of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
a parameter component at the origin, or is always positive or always
negative.
|
Followed.
G.2.4(19): Accuracy Requirements
The versions of the forward trigonometric functions without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain. For the same reason, the
version of Log without a Base parameter should not be
implemented by calling the corresponding version with a Base
parameter of Numerics.e.
|
Followed.
G.2.6(15): Complex Arithmetic Accuracy
The version of the Compose_From_Polar function without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain.
|
Followed.
4 Implementation Defined Characteristics
In addition to the implementation dependent pragmas and attributes, and
the implementation advice, there are a number of other features of Ada
95 that are potentially implementation dependent. These are mentioned
throughout the Ada 95 Reference Manual, and are summarized in annex M.
A requirement for conforming Ada compilers is that they provide
documentation describing how the implementation deals with each of these
issues. In this chapter, you will find each point in annex M listed
followed by a description in italic font of how GNAT
handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation
dependent features in your programs if portability to other compilers
and other operating systems is an important consideration. The numbers
in each section below correspond to the paragraph number in the Ada 95
Reference Manual.
|
2. Whether or not each recommendation given in Implementation
Advice is followed. See 1.1.2(37).
|
See Implementation Advice.
|
3. Capacity limitations of the implementation. See 1.1.3(3).
|
The complexity of programs that can be processed is limited only by the
total amount of available virtual memory, and disk space for the
generated object files.
|
4. Variations from the standard that are impractical to avoid
given the implementation's execution environment. See 1.1.3(6).
|
There are no variations from the standard.
5. Which code_statements cause external
interactions. See 1.1.3(10).
|
Any code_statement can potentially cause external "cartouche" border="1">
If implementation-defined forms of interrupt handler procedures are
supported, such as protected procedures with parameters, then for each
such form of a handler, a type analogous to Parameterless_Handler
should be specified in a child package of Interrupts, with the
same operations as in the predefined package Interrupts.
|
Followed.
C.4(14): Pre-elaboration Requirements
|
It is recommended that pre-elaborated packages be implemented in such a
way that there should be little or no code executed at run time for the
elaboration of entities not already covered by the Implementation
Requirements.
|
Followed. Executable code is generated in some cases, e.g. loops
to initialize large arrays.
C.5(8): Pragma Discard_Names
|
If the pragma applies to an entity, then the implementation should
reduce the amount of storage used for storing names associated with that
entity.
|
Followed.
C.7.2(30): The Package Task_Attributes
|
Some implementations are targeted to domains in which memory use at run
time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first N
attribute objects, and the heap for the others. In the latter case,
N should be documented.
|
Not followed. This implementation is not targeted to such a domain.
D.3(17): Locking Policies
|
The implementation should use names that end with _Locking for
locking policies defined by the implementation.
|
Followed. A single implementation-defined locking policy is defined,
whose name (Inheritance_Locking) follows this suggestion.
D.4(16): Entry Queuing Policies
|
Names that end with _Queuing should be used
for all implementation-defined queuing policies.
|
Followed. No such implementation-defined queuing policies exist.
D.6(9-10): Preemptive Abort
Even though the abort_statement is included in the list of
potentially blocking operations (see 9.5.1), it is recommended that this
statement be implemented in a way that never requires the task executing
the abort_statement to block.
|
Followed.
|
On a multi-processor, the delay associated with aborting a task on
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
|
Followed.
D.7(21): Tasking Restrictions
|
When feasible, the implementation should take advantage of the specified
restrictions to produce a more efficient implementation.
|
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
of restrictions are specified. See pragma Ravenscar and pragma
Restricted_Run_Time for more details.
D.8(47-49): Monotonic Time
When appropriate, implementations should provide configuration
mechanisms to change the value of Tick.
|
Such configuration mechanisms are not appropriate to this implementation
and are thus not supported.
It is recommended that Calendar.Clock and Real_Time.Clock
be implemented as transformations of the same time base.
|
Followed.
It is recommended that the best time base which exists in
the underlying system be available to the application through
Clock. Best may mean highest accuracy or largest range.
|
Followed.
E.5(28-29): Partition Communication Subsystem
|
Whenever possible, the PCS on the called partition should allow for
multiple tasks to call the RPC-receiver with different messages and
should allow them to block until the corresponding subprogram body
returns.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
The Write operation on a stream of type Params_Stream_Type
should raise Storage_Error if it runs out of space trying to
write the Item into the stream.
|
Followed by GLADE, a separately supplied PCS that can be used with
GNAT.
F(7): COBOL Support
If COBOL (respectively, C) is widely supported in the target
environment, implementations supporting the Information Systems Annex
should provide the child package Interfaces.COBOL (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of COBOL (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
F.1(2): Decimal Radix Support
|
Packed decimal should be used as the internal representation for objects
of subtype S when S'Machine_Radix = 10.
|
Not followed. GNAT ignores S'Machine_Radix and always uses binary
representations.
G: Numerics
If Fortran (respectively, C) is widely supported in the target
environment, implementations supporting the Numerics Annex
should provide the child package Interfaces.Fortran (respectively,
Interfaces.C) specified in Annex B and should support a
convention_identifier of Fortran (respectively, C) in the interfacing
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
|
Followed.
G.1.1(56-58): Complex Types
|
Because the usual mathematical meaning of multiplication of a complex
operand and a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
|
Not followed.
Similarly, because the usual mathematical meaning of addition of a
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
complex addition. In implementations in which the Signed_Zeros
attribute of the component type is True (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
|
Not followed.
Implementations in which Real'Signed_Zeros is True should
attempt to provide a rational treatment of the signs of zero results and
result components. As one example, the result of the Argument
function should have the sign of the imaginary component of the
parameter X when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
of the Compose_From_Polar function should be the same as
(respectively, the opposite of) that of the Argument parameter when that
parameter has a value of zero and the Modulus parameter has a
nonnegative (respectively, negative) value.
|
Followed.
G.1.2(49): Complex Elementary Functions
Implementations in which Complex_Types.Real'Signed_Zeros is
True should attempt to provide a rational treatment of the signs
of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
a parameter component at the origin, or is always positive or always
negative.
|
Followed.
G.2.4(19): Accuracy Requirements
The versions of the forward trigonometric functions without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain. For the same reason, the
version of Log without a Base parameter should not be
implemented by calling the corresponding version with a Base
parameter of Numerics.e.
|
Followed.
G.2.6(15): Complex Arithmetic Accuracy
The version of the Compose_From_Polar function without a
Cycle parameter should not be implemented by calling the
corresponding version with a Cycle parameter of
2.0*Numerics.Pi, since this will not provide the required
accuracy in some portions of the domain.
|
Followed.
4 Implementation Defined Characteristics