[Bug c++/106656] New: [C++23] P2513 - char8_t Compatibility and Portability Fixes

[Bug c++/106656] New: [C++23] P2513 - char8_t Compatibility and Portability Fixes

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106656

            Bug ID: 106656
           Summary: [C++23] P2513 - char8_t Compatibility and Portability
                    Fixes
           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/p2513>.

[Bug c++/106656] [C++23] P2513 - char8_t Compatibility and Portability Fixes

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106656

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |mpolacek at gcc dot gnu.org
             Blocks|                            |98940
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2022-08-16
             Status|UNCONFIRMED                 |ASSIGNED


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98940
[Bug 98940] Implement C++23 language features

[Bug c++/106656] [C++23] P2513 - char8_t Compatibility and Portability Fixes

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106656

--- Comment #1 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The trunk branch has been updated by Marek Polacek <mpolacek@gcc.gnu.org>:

https://gcc.gnu.org/g:567329fdd9d65a1e6254206fefff89fa151ba7f3

commit r13-2881-g567329fdd9d65a1e6254206fefff89fa151ba7f3
Author: Marek Polacek <polacek@redhat.com>
Date:   Fri Sep 23 18:06:34 2022 -0400

    c++: P2513R4, char8_t Compatibility and Portability Fix [PR106656]

    P0482R6, which added char8_t, didn't allow

      const char arr[] = u8"howdy";

    because it said "Declarations of arrays of char may currently be
initialized
    with UTF-8 string literals. Under this proposal, such initializations would
    become ill-formed."  This caused too many issues, so P2513R4 alleviates
some
    of those compatibility problems.  In particular, "Arrays of char or
unsigned
    char may now be initialized with a UTF-8 string literal."  This restriction
    has been lifted for initialization only, not implicit conversions.  Also,
    my reading is that 'signed char' was excluded from the allowable
conversions.

    This is supposed to be treated as a DR in C++20.

            PR c++/106656

    gcc/c-family/ChangeLog:

            * c-cppbuiltin.cc (c_cpp_builtins): Update value of __cpp_char8_t
            for C++20.

    gcc/cp/ChangeLog:

            * typeck2.cc (array_string_literal_compatible_p): Allow
            initializing arrays of char or unsigned char by a UTF-8 string
literal.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp23/feat-cxx2b.C: Adjust.
            * g++.dg/cpp2a/feat-cxx2a.C: Likewise.
            * g++.dg/ext/char8_t-feature-test-macro-2.C: Likewise.
            * g++.dg/ext/char8_t-init-2.C: Likewise.
            * g++.dg/cpp2a/char8_t3.C: New test.
            * g++.dg/cpp2a/char8_t4.C: New test.

[Bug c++/106656] [C++23] P2513 - char8_t Compatibility and Portability Fixes

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106656

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

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

--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Implemented in GCC 13.

[Bug c++/106656] [C++23] P2513 - char8_t Compatibility and Portability Fixes

[dmjpp at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106656

Dimitrij Mijoski <dmjpp at hotmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |dmjpp at hotmail dot com

--- Comment #3 from Dimitrij Mijoski <dmjpp at hotmail dot com> ---
The documentation for CLI flag -fchar8_t should be updated
https://gcc.gnu.org/onlinedocs/gcc/C_002b_002b-Dialect-Options.html .

Is there any chance that this fix gets backported because it is treated as
defect report to C++20?

[Bug c++/106656] [C++23] P2513 - char8_t Compatibility and Portability Fixes

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106656

--- Comment #4 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
(In reply to Dimitrij Mijoski from comment #3)
> The documentation for CLI flag -fchar8_t should be updated
> https://gcc.gnu.org/onlinedocs/gcc/C_002b_002b-Dialect-Options.html .

Oh right, this is not an error anymore:
char ca[] = u8"xx";

I'll fix, thanks.

> Is there any chance that this fix gets backported because it is treated as
> defect report to C++20?

I wasn't really planning to do that.