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A GNAT-defined aspect, Local_Restrictions, is defined.
This provides a way of enforcing a given restriction for an individual
subprogram (and its call-closure) without requiring that the entire
program satisfy the restriction.
A GNAT-defined aspect, User_Aspect, is defined.
This (along with the new User_Aspect_Definition configuration pragma) provides
a way of naming a set of aspect specifications which can then be applied
to multiple declarations without textual repetition of the set.
gcc/ada/
* local_restrict.ads: A new package. Declares Local_Restriction
enumeration type and provides operations to check for local
restriction violations.
* local_restrict.adb: Corresponding package body. Replace "not
Present (X)" calls with "No (X)" calls.
* aspects.ads: Add a new enumeration elements,
Aspect_Local_Restrictions and Aspect_User_Aspect, to the Aspect_Id
enumeration type. Update Aspect_Id-indexed aggregates. Add nested
package User_Aspect_Support to manage two pieces of state. One is
a map from identifiers to User_Aspect_Definition pragmas (updated
when such a pragma is encountered). The other is an
access-to-subprogram variable that is introduced in order to keep
the bulk of semantics out of the closure of package Aspects while
allowing a call from aspects.adb to the sem_ch13 procedure that
analyzes a User_Aspect aspect specification.
* aspects.adb (Find_Aspect): Cope with a case of a block statement
with an empty parent. It is not clear whether this is papering
over a compiler bug. Add indirect call through the aforementioned
access-to-subprogram variable when Find_Aspect enounters an
unanalyzed User_Aspect aspect specification. If Find_Aspect is
called looking for aspect Foo, then a User_Aspect specification
might generate (during analysis) a Foo aspect specification. So
the Find_Aspect call needs to trigger that analysis if it has not
already taken place. Provide a body for package
User_Aspect_Support. Replace "not Present (X)" call with "No (X)"
call.
* freeze.adb (Freeze_Subprogram): Check local restriction
compatibility when a dispatching operation is overridden.
* par-prag.adb: Add support for parsing a User_Aspect_Definition
pragma.
* restrict.ads: We'd like to have the body of package Restrict
include a call to a procedure declared in package Local_Restrict.
Doing that in the obvious way pulls most of semantics into the
closure of package Restrict, and that turns out to cause problems.
So we introduce a level of indirection and instead call through an
access-to-subprogram value. In this unit, we declare the
access-to-subprogram type and object.
* restrict.adb (Check Restriction): When a construct is
encountered that could violate a global restriction (depending on
whether the given restriction is in effect), Check_Restriction is
called. At this point, we also check for a violation of any
corresponding local restriction that is in effect. For reasons
described above, this check is performed via an indirect call.
* sem_ch13.ads (Parse_Aspect_Local_Restrictions): A new function,
similar to the existing Parse_Aspect_Xxx subprograms.
* sem_ch13.adb: Perform semantic analysis of Local_Restrictions
and User_Aspect aspect specifications. Declare and call new
Validate_Aspect_Local_Restrictions and
Analyze_User_Aspect_Aspect_Specification procedures (a reference
to the latter is registered during package elaboration). In
Analyze_Aspect_Specifications, do not set the Analyzed flag of a
User_Aspect aspect specification. Replace "not Present (X)" call
with "No (X)" call. Replace 'Image with 'Img in a case where the
prefix of the attribute reference is an object; this is done to
accomodate older compilers.
* sem_ch6.adb (Check_Subtype_Conformant): Include in subtype
conformance check a check for overriding-related compatibility of
local restrictions.
* sem_ch8.adb (Analyze_Subprogram_Renaming): In the case of an
instance of a generic that takes a formal subprogram, check that
formal and actual are compatible with respect to local
restrictions.
* sem_prag.adb: Add support for User_Aspect_Definition pragma.
* sem_res.adb (Resolve_Call): Check caller/callee compatibility
with respect to local restrictions.
* snames.ads-tmpl: Add Name_Local_Restrictions, Name_User_Aspect,
and Name_User_Aspect_Definition constants.
* doc/gnat_rm/implementation_defined_aspects.rst: Document new
aspects.
* doc/gnat_rm/implementation_defined_pragmas.rst: Document new
pragma.
* doc/gnat_ugn/the_gnat_compilation_model.rst: Add
User_Aspect_Definition to list of GNAT pragmas.
* gcc-interface/Make-lang.in: Add local_restrict.o.
* gnat-style.texi: Regenerate.
* gnat_rm.texi: Regenerate.
* gnat_ugn.texi: Regenerate.
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