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

["cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.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.