13.12.1 Language-Defined Restrictions and Profiles
Static Semantics
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AI95-00257-01}
The following
restriction_identifiers
are language defined (additional restrictions are defined in the Specialized
Needs Annexes):
There are no implementation-defined aspects specified by an
aspect_specification.
This restriction applies only to the current compilation or environment,
not the entire partition.
Discussion: {
AI05-0241-1}
This restriction (as well as others below) applies only to the current
compilation, because it is likely that the runtime (and possibly user-written
low-level code) will need to use implementation-defined aspects. But
a partition-wide restriction applies everywhere, including the runtime.
There are no implementation-defined attributes.
There
are no implementation-defined extensions to the definition of any language-defined
attribute (see 4.1.4). This restriction
applies only to the current compilation or environment, not the entire
partition.
There are no usage names that denote declarations with implementation-defined
identifiers that occur within language-defined packages or instances
of language-defined generic packages. Such identifiers can arise as follows:
The following
language-defined packages and generic packages allow implementation-defined
identifiers:
package System (see
13.7);
package Standard (see
A.1);
package Ada.Command_Line (see
A.15);
package Interfaces.C (see
B.3);
package Interfaces.C.Strings (see
B.3.1);
package Interfaces.C.Pointers (see
B.3.2);
package Interfaces.COBOL (see
B.4);
package Interfaces.Fortran (see
B.5);
The following
language-defined packages contain only implementation-defined identifiers:
package System.Machine_Code (see
13.8);
package Ada.Directories.Information
(see
A.16);
nested Implementation packages of
the Queue containers (see
A.18.28-31);
package Interfaces (see
B.2);
package Ada.Interrupts.Names (see
C.3.2).
For package Standard, Standard.Long_Integer
and Standard.Long_Float are considered language-defined identifiers,
but identifiers such as Standard.Short_Short_Integer are considered implementation-defined.
This restriction applies only to the current
compilation or environment, not the entire partition.
There are no implementation-defined pragmas or pragma arguments. This
restriction applies only to the current compilation or environment, not
the entire partition.
There is no mention in the
context_clause
of any implementation-defined descendants of packages Ada, Interfaces,
or System. This restriction applies only to the current compilation or
environment, not the entire partition.
There is no use of language features defined in Annex J. It is implementation
defined whether uses of the renamings of
J.1
and of the
pragmas
of
J.15 are detected by this restriction.
This restriction applies only to the current compilation or environment,
not the entire partition.
Reason: A
user could compile a rename like
with Ada.Text_IO;
package Text_IO renames Ada.Text_IO;
Such a rename must not be disallowed by this
restriction, nor should the compilation of such a rename be restricted
by an implementation. Many implementations implement the renames of
J.1
by compiling them normally; we do not want to require implementations
to use a special mechanism to implement these renames.
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The pragmas have the same functionality as the corresponding aspect (unlike
the typical obsolescent feature), and rejecting them could be a significant
portability problem for existing code.
Specifies a library unit on which there are no semantic dependences.
Identifies an attribute for which no
attribute_reference
or
attribute_definition_clause
is given.
Identifies a
pragma
which is not to be used.
There are no
aspect_specifications
having an unrecognized
aspect_identifier.
This restriction applies only to the current compilation or environment,
not the entire partition.
Ramification: When this restriction is
in effect, unrecognized aspects cannot be ignored in the current compilation;
they violate the restriction. This is true despite the Implementation
Permissions of
13.1.1.
There are no
pragmas
having an unrecognized pragma
identifier.
This restriction applies only to the current compilation or environment,
not the entire partition.
Ramification: When this restriction is
in effect, unrecognized pragmas cannot be ignored in the current compilation;
they violate the restriction. This is true despite the rules of
2.8.
Legality Rules
Ramification: This
name
is not resolved.
Ramification: This
restriction_parameter_argument
is not resolved as it is an identifier specific to a pragma. As for No_Dependence,
there is no check that the aspect
identifier
is meaningful; it might refer to an implementation-defined aspect on
one implementation, but nothing at all on another implementation.
Ramification: This
restriction_parameter_argument
is not resolved as it is an identifier specific to a pragma. There is
no check that the attribute identifier refers to a known
attribute_designator;
it might refer to an implementation-defined attribute on one implementation,
but nothing at all on another implementation.
Ramification: This
restriction_parameter_argument
is not resolved as it is an identifier specific to a pragma. There is
no check that the pragma identifier refers to a known
pragma;
it might refer to an implementation-defined pragma on one implementation,
but nothing at all on another implementation.
Post-Compilation Rules
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AI95-00381-01}
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No compilation unit included in the partition shall depend semantically
on the library unit identified by the
name
of a No_Dependence restriction.
Ramification: {
AI12-0005-1}
There is no requirement that the library unit actually exists. One possible
use of the pragma is to prevent the use of implementation-defined units;
when the program is ported to a different compiler, it is perfectly reasonable
that no unit with the name exists.
Static Semantics
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AI05-0246-1}
The No_Implementation_Extensions usage profile is equivalent to the following
restrictions:
No_Implementation_Aspect_Specifications,
No_Implementation_Attributes,
No_Implementation_Identifiers,
No_Implementation_Pragmas,
No_Implementation_Units.
Extensions to Ada 95
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AI95-00257-01}
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AI95-00368-01}
Restrictions No_Implementation_Attributes, No_Implementation_Pragmas,
and No_Obsolescent_Features are new.
Extensions to Ada 2005
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AI05-0241-1}
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AI05-0242-1}
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AI05-0246-1}
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AI05-0272-1}
Restrictions No_Implementation_Aspect_Specifications,
No_Implementation_Identifiers, No_Implementation_Units, No_Specification_of_Aspect,
No_Use_of_Attribute, and No_Use_of_Pragma are new.
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AI05-0246-1}
Profile No_Implementation_Extensions is new.
Extensions to Ada 2012
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AI12-0389-1}
Restrictions No_Unrecognized_Aspects and No_Unrecognized_Pragmas
are new.
Wording Changes from Ada 2022
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AI22-0004-1}
Corrigendum: Clarified that the restriction
No_Implementation_Attributes includes any implementation-defined extensions
to language-defined attributes allowed by 4.1.4.
Ada 2005 and 2012 Editions sponsored in part by Ada-Europe
