[Bug tree-optimization/81452] warn on realloc(p, 0)

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81452

--- Comment #3 from Martin Sebor <msebor at gcc dot gnu.org> ---
There is -Walloc-zero.  If we want a separate knob for just it then maybe
-Wrealloc-zero.