[Bug c++/110341] New: [C++26] P1854R4 - Making non-encodable string literals ill-formed

[Bug c++/110341] New: [C++26] P1854R4 - Making non-encodable string literals ill-formed

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110341

            Bug ID: 110341
           Summary: [C++26] P1854R4 - Making non-encodable string literals
                    ill-formed
           Product: gcc
           Version: 14.0
            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/P1854R4>.

[Bug c++/110341] [C++26] P1854R4 - Making non-encodable string literals ill-formed

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110341

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I don't think there is anything to do for this paper:
`GCC exposes the same behavior(the one proposed by this paper) in all language
modes.`

[Bug c++/110341] [C++26] P1854R4 - Making non-encodable string literals ill-formed

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110341

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2023-06-21
     Ever confirmed|0                           |1

--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
It's possible/likely; I haven't actually read the paper yet.  We want to add
any possible testcases.  I should be able to address this by the end of next
week if nobody beats me to it.

[Bug c++/110341] [C++26] P1854R4 - Making non-encodable string literals ill-formed

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110341

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |jakub at gcc dot gnu.org

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 55795
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=55795&action=edit
gcc14-pr110341.patch

Untested implementation.

[Bug c++/110341] [C++26] P1854R4 - Making non-encodable string literals ill-formed

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110341

--- Comment #4 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:194825f20619a1c4b51eaea84f20432fefc0db03

commit r14-5454-g194825f20619a1c4b51eaea84f20432fefc0db03
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Tue Nov 14 18:28:34 2023 +0100

    c++: Implement C++26 P1854R4 - Making non-encodable string literals
ill-formed [PR110341]

    This paper voted in as DR makes some multi-character literals ill-formed.
    'abcd' stays valid, but e.g. 'á' is newly invalid in UTF-8 exec charset
    while valid e.g. in ISO-8859-1, because it is a single character which
needs
    2 bytes to be encoded.

    The following patch does that by checking (only pedantically, especially
    because it is a DR) if we'd emit a -Wmultichar warning because character
    constant has more than one byte in it whether the number of source
characters
    is equal to the number of bytes in the multichar string.
    If it is, it is normal multi-character literal constant
    and is diagnosed normally with -Wmultichar, otherwise at least one of the
    c-chars in the sequence was encoded as 2+ bytes.

    2023-11-14  Jakub Jelinek  <jakub@redhat.com>

            PR c++/110341
    libcpp/
            * charset.cc: Implement C++26 P1854R4 - Making non-encodable string
            literals ill-formed.
            (one_count_chars, convert_count_chars, count_source_chars): New
            functions.
            (narrow_str_to_charconst): Change last arg type from cpp_ttype to
            const cpp_token *.  For C++ if pedantic and i > 1 in CPP_CHAR
            interpret token also as CPP_STRING32 and if number of characters
            in the CPP_STRING32 is larger than number of bytes in CPP_CHAR,
            pedwarn on it.  Make the diagnostics more detailed.
            (wide_str_to_charconst): Change last arg type from cpp_ttype to
            const cpp_token *.  Make the diagnostics more detailed.
            (cpp_interpret_charconst): Adjust narrow_str_to_charconst and
            wide_str_to_charconst callers.
    gcc/testsuite/
            * g++.dg/cpp26/literals1.C: New test.
            * g++.dg/cpp26/literals2.C: New test.
            * g++.dg/cpp23/wchar-multi1.C: Adjust expected diagnostic wordings.
            * g++.dg/cpp23/wchar-multi2.C: Likewise.
            * gcc.dg/c23-utf8char-3.c: Likewise.
            * gcc.dg/cpp/charconst-4.c: Likewise.
            * gcc.dg/cpp/charconst.c: Likewise.
            * gcc.dg/cpp/if-2.c: Likewise.
            * gcc.dg/utf16-4.c: Likewise.
            * gcc.dg/utf32-4.c: Likewise.
            * g++.dg/cpp1z/utf8-neg.C: Likewise.
            * g++.dg/cpp2a/ucn2.C: Likewise.
            * g++.dg/ext/utf16-4.C: Likewise.
            * g++.dg/ext/utf32-4.C: Likewise.

[Bug c++/110341] [C++26] P1854R4 - Making non-encodable string literals ill-formed

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110341

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

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

--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Implemented for GCC 14 now.