Re: [PATCH] xrealloc: do not reuse pointer freed by zero-length realloc()

From: Jonathan Nieder <jrnieder@gmail.com>
To: Junio C Hamano <gitster@pobox.com>
Cc: Jeff King <peff@peff.net>, Derrick Stolee <stolee@gmail.com>,
	git@vger.kernel.org
Subject: Re: [PATCH] xrealloc: do not reuse pointer freed by zero-length realloc()
Date: Wed, 2 Sep 2020 20:50:08 -0700	[thread overview]
Message-ID: <20200903035008.GF4035286@google.com> (raw)
In-Reply-To: <xmqq3641ebep.fsf@gitster.c.googlers.com>

Junio C Hamano wrote:
> 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.

I agree with both points: if we were repeatedly shrinking and growing
a buffer and cared about its performance, then we'd want the first
version, and since we aren't, we should prefer this version that is
more readable.

Thanks,
Jonathan