https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70180
--- Comment #4 from Martin Sebor <msebor at gcc dot gnu.org> ---
With -Wextra, Clang warns on one of the cases:
70180.cc:3:22: warning: performing pointer arithmetic on a null pointer has
undefined behavior if the offset is nonzero [-Wnull-pointer-arithmetic]
void *p = (int*)NULL + 1;
~~~~~~~~~~ ^
