Can memset() be called with a null pointer if the size is 0?

For one reason or another, I want to hand-roll a zeroing version of `malloc()`. To minimize algorithmic complexity, I want to write: ``` void * my_calloc(size_t size) { return memset(malloc(size), 0, size); } ``` Is this well-defined when `size == 0`? It is fine to call `malloc()` with a zero size, but that allows it to return a null pointer. Will the subsequent invocation of `memset` be OK, or is this undefined behaviour and I need to add a conditional `if (size)`? I would very much want to avoid redundant conditional checks! Assume for the moment that `malloc()` doesn't fail. In reality there'll be a hand-rolled version of `malloc()` there, too, which will terminate on failure. Something like this: ``` void * my_malloc(size_t size) { void * const p = malloc(size); if (p || 0 == size) return p; terminate(); } ```