On Tue, Sep 01, 2020 at 09:04:36AM -0400, Derrick Stolee wrote:
> > The simplest fix here is to just pass "ret" (which we know to be NULL)
> > to the follow-up realloc(). That does mean that a system which _doesn't_
> > free the original pointer would leak it. But that interpretation of the
> > standard seems unlikely (if a system didn't deallocate in this case, I'd
> > expect it to simply return the original pointer). If it turns out to be
> > an issue, we can handle the "!size" case up front instead, before we
> > call realloc() at all.
>
> Adding an `if (!size) {free(ptr); return NULL;}` block was what I
> expected. Was that chosen just so we can rely more on the system
> realloc(), or is there a performance implication that I'm not
> seeing?
I went back and forth on whether to do that or not. This case should
basically never happen, so I like both the performance and readability
of only triggering it when realloc() returns NULL. But it would get rid
of the hand-waving above, and I doubt the performance is measurable.
If we do handle it up-front, then I think we'd actually want:
if (!size) {
free(ptr);
return xmalloc(0);
}
(i.e., to never return NULL for consistency with xmalloc() and
xcalloc()).
> > @@ -120,7 +120,7 @@ void *xrealloc(void *ptr, size_t size)
> > memory_limit_check(size, 0);
> > ret = realloc(ptr, size);
> > if (!ret && !size)
> > - ret = realloc(ptr, 1);
> > + ret = realloc(ret, 1);
>
> I appreciate all the additional context for such a small change.
Somebody's got to complete with you for ratio of commit message to diff
lines. :)
-Peff
