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Subject: [Bug c/111884] [13/14 Regression] unsigned char no longer aliases
 anything under -std=c2x
Date: Fri, 20 Oct 2023 19:37:45 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D111884

--- Comment #5 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:281699fbff6262766674ab13087d37db751cd40a

commit r14-4802-g281699fbff6262766674ab13087d37db751cd40a
Author: Marek Polacek <polacek@redhat.com>
Date:   Thu Oct 19 16:32:10 2023 -0400

    c-family: char8_t and aliasing in C vs C++ [PR111884]

    In the PR, Joseph says that in C char8_t is not a distinct type.  So
    we should behave as if it can alias anything, like ordinary char.
    In C, unsigned_char_type_node =3D=3D char8_type_node, so with this patch
    we return 0 instead of -1.  And the following comment says:

      /* The C standard guarantees that any object may be accessed via an
         lvalue that has narrow character type (except char8_t).  */
      if (t =3D=3D char_type_node
          || t =3D=3D signed_char_type_node
          || t =3D=3D unsigned_char_type_node)
        return 0;

    Which appears to be wrong, so I'm adjusting that as well.

            PR c/111884

    gcc/c-family/ChangeLog:

            * c-common.cc (c_common_get_alias_set): Return -1 for char8_t o=
nly
            in C++.

    gcc/testsuite/ChangeLog:

            * c-c++-common/alias-1.c: New test.=