glibc string.h declares memcpy() with attribute(nonnull(1,2)), causing
calls with NULL arguments to be treated as undefined behaviour.
This is consistent with ISO C99 and C11, which state that passing 0
to string functions as an array length does not remove the requirement
that the pointer to the array is a valid pointer.
gcc -fsanitize=undefined catches this while running OSTree's test suite.
Similarly, running the GLib test suite reports similar issues for
qsort(), memmove(), memcmp().
Signed-off-by: Simon McVittie <smcv@debian.org>
Bug: https://bugzilla.gnome.org/show_bug.cgi?id=775510
Reviewed-by: Colin Walters
