[Bug libstdc++/94003] is_constructible seems to have sideeffects

[Bug libstdc++/94003] is_constructible seems to have sideeffects

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94003

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Depends on|                            |41437

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Almost certainly due to one of the bugs linked to PR 59002, probably PR 41437.

Inside the function template access checking doesn't work properly, so you can
use the private constructor, and the first instantiation of the trait gives the
wrong answer:

template <typename X> static bool why() {
  Class c;
  return std::is_constructible<Class>::value;
}

Then when the trait is rechecked later it has already been instantiated, and so
continues to give the wrong answer.


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=41437
[Bug 41437] No access control for classes in template functions

[Bug libstdc++/94003] is_constructible seems to have sideeffects

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94003

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Patrick Palka <ppalka@gcc.gnu.org>:

https://gcc.gnu.org/g:92bed036098928cd4659c8990e14cf7ad040e0c2

commit r11-1350-g92bed036098928cd4659c8990e14cf7ad040e0c2
Author: Patrick Palka <ppalka@redhat.com>
Date:   Tue Jun 16 08:21:33 2020 -0400

    c++: Improve access checking inside templates [PR41437]

    This patch generalizes our existing functionality for deferring access
    checking of typedefs when parsing a function or class template to now
    defer all kinds of access checks until template instantiation time,
    including member function and member object accesses.

    Since all access checks eventually go through enforce_access, the main
    component of this patch is new handling inside enforce_access to defer
    the current access check if we're inside a template.  The bulk of the
    rest of the patch consists of removing now-unneeded code pertaining to
    suppressing access checks inside templates or pertaining to
    typedef-specific access handling.  Renamings and other changes with no
    functional impact have been split off into the followup patch.

    gcc/cp/ChangeLog:

            PR c++/41437
            PR c++/47346
            * call.c (enforce_access): Move to semantics.c.
            * cp-tree.h (enforce_access): Delete.
            (get_types_needing_access_check): Delete.
            (add_typedef_to_current_template_for_access_check): Delete.
            * decl.c (make_typename_type): Adjust accordingly.  Use
            check_accessibility_of_qualified_id instead of directly using
            perform_or_defer_access_check.
            * parser.c (cp_parser_template_declaration_after_parameters):
            Don't push a dk_no_check access state when parsing a template.
            * pt.c (get_types_needing_access_check): Delete.
            (append_type_to_template_for_access_check_1): Delete.
            (perform_typedefs_access_check): Adjust.  If type_decl is a
            FIELD_DECL, also check its DECL_CONTEXT for dependence. Use
            tsubst_copy instead of tsubst to substitute into type_decl so
            that we substitute into the DECL_CONTEXT of a FIELD_DECL.
            (append_type_to_template_for_access_check): Delete.
            * search.c (accessible_p): Remove the processing_template_decl
            early exit.
            * semantics.c (enforce_access): Moved from call.c.  If we're
            parsing a template and the access check failed, add the check to
            TI_TYPEDEFS_NEEDING_ACCESS_CHECKING.
            (perform_or_defer_access_check): Adjust comment.
            (add_typedef_to_current_template_for_access_check): Delete.
            (check_accessibility_of_qualified_id):  Adjust accordingly.
            Exit early if the scope is dependent.

    gcc/testsuite/ChangeLog:

            PR c++/41437
            PR c++/47346
            * g++.dg/cpp2a/concepts-using2.C: Adjust.
            * g++.dg/lto/20081219_1.C: Adjust.
            * g++.dg/lto/20091002-1_0.C: Adjust.
            * g++.dg/lto/pr65475c_0.C: Adjust.
            * g++.dg/opt/dump1.C: Adjust.
            * g++.dg/other/pr53574.C: Adjust.
            * g++.dg/template/access30.C: New test.
            * g++.dg/template/access31.C: New test.
            * g++.dg/wrappers/wrapper-around-type-pack-expansion.C: Adjust.

    libstdc++-v3/ChangeLog:

            PR libstdc++/94003
            * testsuite/20_util/is_constructible/94003.cc: New test.

[Bug libstdc++/94003] is_constructible seems to have sideeffects

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94003
Bug 94003 depends on bug 41437, which changed state.

Bug 41437 Summary: No access control for classes in template functions
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=41437

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

[Bug libstdc++/94003] is_constructible seems to have sideeffects

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94003

Patrick Palka <ppalka at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ppalka at gcc dot gnu.org
   Target Milestone|---                         |11.0
         Resolution|---                         |FIXED
             Status|NEW                         |RESOLVED

--- Comment #4 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Fixed for GCC 11.