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

Hye-Shik Chang perky at i18n.org
Sun Jan 18 16:20:29 EST 2004

On Sun, Jan 18, 2004 at 03:09:13PM -0600, Jeff Epler wrote:

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.

Thanks for the explanation. But listobject isn't using realloc and ob_item == NULL case is concerned in the code already.

In PyList_New: 73 if (size <= 0) { 74 op->ob_item = NULL; 75 }

Excuse me but am I missed something?

Hye-Shik

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