[Python-Dev] Re: [Python-checkins] python/dist/src/Objects listobject.c, 2.176, 2.177 (original) (raw)

Jeff Epler jepler at unpythonic.net
Sun Jan 18 16:09:13 EST 2004

On Mon, Jan 19, 2004 at 05:48:38AM +0900, Hye-Shik Chang wrote:

Is there a particular reason for allocating zero-sized memory for this? On my test, assigning NULL on self->obitem instead is worked either.

Yes. I think that the explanation goes something like this:

Only values returned by malloc/calloc/realloc are suitable as an argument to realloc/free. So, if you want to start with 0 bytes but not special case the deallocation or reallocation case, you write f = malloc(0); instead of f = NULL; later, you can use f = realloc(f, newsize); /* Ignoring error checking */ and f = free(f) instead of if (f) f = realloc(f, newsize); else f = malloc(newsize); and if(f) free(f);

now, some systems have malloc(0) return NULL, and accept free(NULL) as a no-op, and realloc(NULL, newsize) as malloc(newsize), but behavior other than that is allowed by the C standard.

Jeff

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