[Bug c++/114519] New: GCC 14 trunk fails to compile chrono with -fno-char8_t -std=gnu++20

[Bug c++/114519] New: GCC 14 trunk fails to compile chrono with -fno-char8_t -std=gnu++20

[janisozaur+gcc at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114519

            Bug ID: 114519
           Summary: GCC 14 trunk fails to compile chrono with -fno-char8_t
                    -std=gnu++20
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: janisozaur+gcc at gmail dot com
  Target Milestone: ---

Created attachment 57830
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=57830&action=edit
failure log gcc 20240328

Godbolt link:
https://godbolt.org/z/e8GG8znTh

test.cpp:
#include <chrono>

Compilation:
g++ -std=gnu++20 -fno-char8_t

Version:
/home/mijn/workspace/gcc-install-master/bin/g++ --version                       
g++ (GCC) 14.0.1 20240328 (experimental)
Copyright (C) 2024 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Expected result:
compiles without issues. It compiles correctly with GCC 13

Result:
Full output in the attachment, only the last line quoted below:

/opt/compiler-explorer/gcc-trunk-20240328/include/c++/14.0.1/format:707:58:
error: 'consteval bool std::__unicode::__literal_encoding_is_unicode() [with
_CharT = char]' called in a constant expression
  707 |       if constexpr (__literal_encoding_is_unicode<_CharT>())
      |                     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~
Compiler returned: 1

[Bug libstdc++/114519] GCC 14 trunk fails to compile chrono with -fno-char8_t -std=gnu++20

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114519

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|c++                         |libstdc++

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Why are you using fno-char8_t? It turns off features of c++ that the standard
library requires.

[Bug libstdc++/114519] GCC 14 trunk fails to compile chrono with -fno-char8_t -std=gnu++20

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114519

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2024-03-28
   Target Milestone|---                         |14.0
           Assignee|unassigned at gcc dot gnu.org      |redi at gcc dot gnu.org
             Status|UNCONFIRMED                 |ASSIGNED
     Ever confirmed|0                           |1

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
The library doesn't require it, and can cope with -fno-char8_t

[Bug libstdc++/114519] GCC 14 trunk fails to compile chrono with -fno-char8_t -std=gnu++20

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114519

--- Comment #3 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jonathan Wakely <redi@gcc.gnu.org>:

https://gcc.gnu.org/g:21aa57e73b820395b7b01843d61ef5b84cd20d02

commit r14-9761-g21aa57e73b820395b7b01843d61ef5b84cd20d02
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Thu Mar 28 21:29:17 2024 +0000

    libstdc++: Guard uses of char8_t with __cpp_char8_t [PR114519]

    libstdc++-v3/ChangeLog:

            PR libstdc++/114519
            * include/bits/unicode.h (_Utf8_view): Guard with check for
            char8_t being enabled.
            (__literal_encoding_is_unicode): Guard use of char8_t with check
            for it being enabled.
            * testsuite/std/format/functions/114519.cc: New test.

[Bug libstdc++/114519] [14 Regression] GCC 14 trunk fails to compile chrono with -fno-char8_t -std=gnu++20

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114519

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|ASSIGNED                    |RESOLVED
      Known to work|                            |13.2.0
      Known to fail|                            |14.0
            Summary|GCC 14 trunk fails to       |[14 Regression] GCC 14
                   |compile chrono with         |trunk fails to compile
                   |-fno-char8_t -std=gnu++20   |chrono with -fno-char8_t
                   |                            |-std=gnu++20

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Fixed, thanks for the report.

[Bug libstdc++/114519] [14 Regression] GCC 14 trunk fails to compile chrono with -fno-char8_t -std=gnu++20

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114519

--- Comment #5 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jonathan Wakely <redi@gcc.gnu.org>:

https://gcc.gnu.org/g:feb6a2d3569095706170c9400e93add27a66e034

commit r14-9839-gfeb6a2d3569095706170c9400e93add27a66e034
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Tue Apr 2 22:46:55 2024 +0100

    libstdc++: Use char for _Utf8_view if char8_t isn't available [PR114519]

    Instead of just omitting the definition of __unicode::_Utf8_view when
    char8_t is disabled, we can make it use char instead.

    libstdc++-v3/ChangeLog:

            PR libstdc++/114519
            * include/bits/unicode.h (_Utf8_view) [!__cpp_char8_t]: Define
            using char instead of char8_t.
            * testsuite/ext/unicode/view.cc: Use u8""sv literals to create
            string views, instead of std::u8string_view.