[Python-Dev] Problem with the memory docs (original) (raw)

Tim Peters tim.one@comcast.net
Wed, 03 Apr 2002 23:11:11 -0500

The docs for PyMem_Malloc say:

Requesting zero bytes returns a non-NULL pointer.

I can't guarantee this without insane effort, and our code has never guaranteed this. If pymalloc or the platform allocator can't even allocate one byte in this case, nothing can be done to guarantee it except to return "an address" fabricated out of thin air, and guaranteed not to match any legitimate address. Then realloc and free would have to special-case the snot out of those fabricated addresses to avoid going insane. Note that C does not guarantee malloc(0) will return a non-NULL pointer, even on platforms where malloc(0) tries to return a non-NULL pointer. It doesn't have a choice about this: since all non-NULL addresses returned by a conforming C malloc() have to be pairwise distinct so long as none are free()'ed, you can provoke any C implementation into returning NULL for malloc(0) just by calling malloc(0) often enough without doing any free()s.

I vote to change the docs. If you vote for something else, you implement it .