From: Junio C Hamano <gitster@pobox.com>
Date: Tue, 01 Sep 2020 15:58:54 GMT
Subject: Re: [PATCH] xrealloc: do not reuse pointer freed by zero-length realloc()
Message-ID: <xmqq3641ebep.fsf@gitster.c.googlers.com>
In-Reply-To: <20200901135105.GA3284077@coredump.intra.peff.net>

Jeff King <peff@peff.net> writes:

> 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()).

Makes sense.  I suspect that this is optimizing for a wrong case,
but in practice that should not matter.  Not having to worry about
a request to resize to 0-byte in the remainder of the function is
actually a plus for readability, I would say.

>> > @@ -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