[Bug libstdc++/87787] [UBSAN] runtime error: null pointer passed as argument 2, which is declared to never be null

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87787

--- Comment #13 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Author: redi
Date: Fri Feb  8 14:16:28 2019
New Revision: 268694

URL: https://gcc.gnu.org/viewcvs?rev=268694&root=gcc&view=rev
Log:
PR libstdc++/87787 avoid undefined null args to memcpy and memmove

The C++ char_traits and ctype APIs do not disallow null pointer
arguments, so we need explicit checks to ensure we don't forward null
pointers to memcpy or memmove.

Backport from mainline
2019-01-07  Jonathan Wakely  <jwak...@redhat.com>

        PR libstdc++/87787
        * include/bits/char_traits.h (char_traits::move): Do not pass null
        pointers to memmove.
        * include/bits/locale_facets.h
        (ctype<char>::widen(const char*, const char*, char*)): Do not
        pass null pointers to memcpy.
        (ctype<char>::narrow(const char*, const char*, char, char*)):
        Likewise.
        (ctype<char>::do_widen(const char*, const char*, char*)):
        Likewise.
        (ctype<char>::do_narrow(const char*, const char*, char, char*)):
        Likewise.

Modified:
    branches/gcc-8-branch/libstdc++-v3/ChangeLog
    branches/gcc-8-branch/libstdc++-v3/include/bits/char_traits.h
    branches/gcc-8-branch/libstdc++-v3/include/bits/locale_facets.h