[Bug libstdc++/110133] New: System error message should ideally use strerror_r over strerror

[Bug libstdc++/110133] New: System error message should ideally use strerror_r over strerror

[romain.geissler at amadeus dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110133

            Bug ID: 110133
           Summary: System error message should ideally use strerror_r
                    over strerror
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: romain.geissler at amadeus dot com
  Target Milestone: ---

Hi,

Checking the source code, it seems that the underlying implementation of
generic_category/system_category message() function uses this code:

    return string(strerror(i));

which happens to be thread safe when targetting glibc, but that remains an
implementation details, and not necessarily all libc implement this behavior.
Ideally strerror_r shall be used when available.

Note that unfortunately, glibc has two strerror_r implementations, with a
different return type and thus a different behavior. As an example to cope with
both behavior libc++ choose to use this overloading mechanism:
https://github.com/llvm/llvm-project/blob/2bd82c5462d511f1e58e7d9a4dcd5628cd16a32d/libcxx/src/system_error.cpp#LL114C8-L114C21

In the gcc project, the maintainers of libgfortran have implemented a similar
change this way:
https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=723553bdc16695ecc686a2ffdff6d15bd600b676;hp=62f9aedcd0a97001f290a1c13fa66efd207a23cc

[Bug libstdc++/110133] System error message should ideally use strerror_r over strerror

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110133

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2023-06-05
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Romain Geissler from comment #0)
> Ideally strerror_r shall be used when available.

Or strerrordesc_np.

[Bug libstdc++/110133] System error message should ideally use strerror_r over strerror

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110133

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I've also considered using strerror_l (with newlocale and uselocale), so that
the strings are not affected by the current locale.

[Bug libstdc++/110133] System error message should ideally use strerror_r over strerror

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110133

--- Comment #3 from CVS 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:51f94778b45514992a716b0b2d7a87244e6f0018

commit r14-5123-g51f94778b45514992a716b0b2d7a87244e6f0018
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Fri Nov 3 13:59:48 2023 +0000

    libstdc++: Use strerror_r in std::generic_category()::message(int)
[PR110133]

    Use strerror_r instead of strerror when available, due to the latter not
    being thread-safe. This is complicated by Glibc providing a GNU-specific
    strerror_r which is not compatible with POSIX strerror_r, so we need to
    dispatch on the return type.

    We can use the recently-added std::string::__resize_and_overwrite to
    write directly into the string buffer when possible. Because we estimate
    the initial buffer size we might end up with excess capacity in the
    returned std::string. We can slightly tweak the std::system_error
    constructors to make use of that excess capacity, so that in some cases
    we require fewer allocations to construct the std::system_error::what()
    string.

    libstdc++-v3/ChangeLog:

            PR libstdc++/110133
            * include/std/system_error (system_error::system_error): Group
            arguments so that concatenation can reuse rvalue's capacity.
            * src/c++11/system_error.cc (strerror_string): New function.
            [_GLIBCXX_HAVE_STRERROR_R] (use_strerror_result): New functions.
            (generic_error_category::message): Use strerror_string.
            (system_error_category::message): Likewise.

[Bug libstdc++/110133] System error message should ideally use strerror_r over strerror

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110133

--- Comment #4 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-13 branch has been updated by Jonathan Wakely
<redi@gcc.gnu.org>:

https://gcc.gnu.org/g:ca233ac9ba085e2acd385bda6a778684a0c96694

commit r13-8129-gca233ac9ba085e2acd385bda6a778684a0c96694
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Fri Nov 3 13:59:48 2023 +0000

    libstdc++: Use strerror_r in std::generic_category()::message(int)
[PR110133]

    Use strerror_r instead of strerror when available, due to the latter not
    being thread-safe. This is complicated by Glibc providing a GNU-specific
    strerror_r which is not compatible with POSIX strerror_r, so we need to
    dispatch on the return type.

    Because we estimate the initial std::string buffer size we might end up
    with excess capacity in the returned std::string. We can slightly tweak
    the std::system_error constructors to make use of that excess capacity,
    so that in some cases we require fewer allocations to construct the
    std::system_error::what() string.

    libstdc++-v3/ChangeLog:

            PR libstdc++/110133
            * include/std/system_error (system_error::system_error): Group
            arguments so that concatenation can reuse rvalue's capacity.
            * src/c++11/system_error.cc (strerror_string): New function.
            [_GLIBCXX_HAVE_STRERROR_R] (use_strerror_result): New functions.
            (generic_error_category::message): Use strerror_string.
            (system_error_category::message): Likewise.

    (cherry picked from commit 51f94778b45514992a716b0b2d7a87244e6f0018)

[Bug libstdc++/110133] System error message should ideally use strerror_r over strerror

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110133

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
   Target Milestone|---                         |13.3
         Resolution|---                         |FIXED

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Fixed for 13.3, I don't think I'll backport it further.