[Bug libstdc++/95851] [10/11 Regression] std::to_chars(p, p, c, 2) segfault

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95851

--- Comment #2 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Jonathan Wakely
<redi@gcc.gnu.org>:

https://gcc.gnu.org/g:ff5c8fe44a98025c1e700cfc033247965e293869

commit r10-8360-gff5c8fe44a98025c1e700cfc033247965e293869
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Tue Jun 23 22:47:58 2020 +0100

    libstdc++: Fix std::to_chars buffer overflow (PR 95851)

    The __detail::__to_chars_2 function assumes it won't be called with zero
    values. However, when the output buffer is empty the caller doesn't
    handle zero values correctly, and calls __to_chars_2 with a zero value,
    resulting in an overflow of the empty buffer.

    The __detail::__to_chars_i function should just return immediately for
    an empty buffer, and otherwise ensure zero values are handled properly.

    libstdc++-v3/ChangeLog:

            PR libstdc++/95851
            * include/std/charconv (__to_chars_i): Check for zero-sized
            buffer unconditionally.
            * testsuite/20_util/to_chars/95851.cc: New test.

    (cherry picked from commit be50843754b4c4d47f0d628a84b3dbf2a4145a43)