[Bug c++/102612] New: [C++23] P2242R3 - Non-literal variables (and labels and gotos) in constexpr functions

[Bug c++/102612] New: [C++23] P2242R3 - Non-literal variables (and labels and gotos) in constexpr functions

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102612

            Bug ID: 102612
           Summary: [C++23] P2242R3 - Non-literal variables (and labels
                    and gotos) in constexpr functions
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mpolacek at gcc dot gnu.org
  Target Milestone: ---

See https://wg21.link/p2242r3

[Bug c++/102612] [C++23] P2242R3 - Non-literal variables (and labels and gotos) in constexpr functions

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102612

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |jakub at gcc dot gnu.org
             Status|UNCONFIRMED                 |ASSIGNED
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2021-10-05

--- Comment #1 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Patch posted:
https://gcc.gnu.org/pipermail/gcc-patches/2021-October/580960.html

[Bug c++/102612] [C++23] P2242R3 - Non-literal variables (and labels and gotos) in constexpr functions

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102612

--- Comment #2 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:8892d532d66910e518bc135a851a104322385ca2

commit r12-4206-g8892d532d66910e518bc135a851a104322385ca2
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Wed Oct 6 10:28:31 2021 +0200

    c++: Implement C++23 P2242R3 - Non-literal variables (and labels and gotos)
in constexpr functions [PR102612]

    The following patch implements C++23 P2242R3 - Non-literal variables
    (and labels and gotos) in constexpr functions.
    I think it is mostly straightforward, don't diagnose certain
    statements/declarations just because of their presence in
    constexpr/consteval functions, but (except for the non-literal type
    var declarations which ought to be caught by e.g. constructor or
    destructor call during evaluation not being constexpr and for
    labels which are now always allowed) diagnose it during constexpr
    evaluation.

    2021-10-06  Jakub Jelinek  <jakub@redhat.com>

            PR c++/102612
    gcc/c-family/
            * c-cppbuiltin.c (c_cpp_builtins): For -std=c++23 predefine
            __cpp_constexpr to 202110L rather than 201907L.
    gcc/cp/
            * parser.c (cp_parser_jump_statement): Implement C++23 P2242R3.
            Allow goto expressions in constexpr function bodies for C++23.
            Adjust error message for older standards to mention it.
            * decl.c (start_decl): Allow static and thread_local declarations
            in constexpr function bodies for C++23.  Adjust error message for
            older standards to mention it.
            * constexpr.c (ensure_literal_type_for_constexpr_object): Allow
            declarations of variables with non-literal type in constexpr
function
            bodies for C++23.  Adjust error message for older standards to
mention
            it.
            (cxx_eval_constant_expression) <case DECL_EXPR>: Diagnose
declarations
            of initialization of static or thread_local vars.
            (cxx_eval_constant_expression) <case GOTO_EXPR>: Diagnose goto
            statements for C++23.
            (potential_constant_expression_1) <case DECL_EXPR>: Swap the
            CP_DECL_THREAD_LOCAL_P and TREE_STATIC checks.
            (potential_constant_expression_1) <case LABEL_EXPR>: Allow labels
for
            C++23.  Adjust error message for older standards to mention it.
    gcc/testsuite/
            * g++.dg/cpp23/feat-cxx2b.C: Expect __cpp_constexpr 202110L rather
            than 201907L.
            * g++.dg/cpp23/constexpr-nonlit1.C: New test.
            * g++.dg/cpp23/constexpr-nonlit2.C: New test.
            * g++.dg/cpp23/constexpr-nonlit3.C: New test.
            * g++.dg/cpp23/constexpr-nonlit4.C: New test.
            * g++.dg/cpp23/constexpr-nonlit5.C: New test.
            * g++.dg/cpp23/constexpr-nonlit6.C: New test.
            * g++.dg/diagnostic/constexpr1.C: Only expect some diagnostics for
            c++20_down.
            * g++.dg/cpp1y/constexpr-label.C: Likewise.
            * g++.dg/cpp1y/constexpr-neg1.C: Likewise.
            * g++.dg/cpp2a/constexpr-try5.C: Likewise.  Adjust some expected
            wording.
            * g++.dg/cpp2a/constexpr-dtor3.C: Likewise.
            * g++.dg/cpp2a/consteval3.C: Likewise.  Add effective target c++20
            and remove dg-options.

[Bug c++/102612] [C++23] P2242R3 - Non-literal variables (and labels and gotos) in constexpr functions

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102612

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

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

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Implemented for GCC 12.