[Bug c/121846] call to memcpy with zero value n argument triggers deletion of null pointer check optimization

[sjames at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121846

--- Comment #6 from Sam James <sjames at gcc dot gnu.org> ---
(I did start implementing that for glibc a little while ago, it's easy, just
tedious, and dunno if we'd consider that backportable, while stripping nonnull
should be certainly backported.)