Why doesn't free() zero out the memory prior to releasing it?

Question

When we free() memory in C, why is that memory not filled with zero? Is there a good way to ensure this happens as a matter of course when calling free()<

Answer 1

Setting the result of a freed pointer to zero may seem to be bullshit, but if the pointer is inadvertently accessed later, you'll get a segfault (at least in a real OS), and the debugger will point to where this abomination is happening. But as others have noted, when you call "free" later, all free has is the address to free, and nothing else.