Re: [PATCH 4/6] abbrev_sha1_in_line: don't leak memory

From: Jeff King <peff@peff.net>
Date: Mar 30, 2016, 17:21 UTC
Message-ID: <20160330172157.GA19675@sigill.intra.peff.net>
In-Reply-To: <xmqqzitfuc7y.fsf@gitster.mtv.corp.google.com>

On Wed, Mar 30, 2016 at 10:06:41AM -0700, Junio C Hamano wrote:

Show 26 quoted lines

> Jeff King <peff@peff.net> writes:
> 
> > On Tue, Mar 29, 2016 at 09:30:38PM -0400, Eric Sunshine wrote:
> >
> >> The implementation of strbuf_list_free() is this:
> >> 
> >>     struct strbuf **s = sbs;
> >>     while (*s) {
> >>         strbuf_release(*s);
> >>         free(*s++);
> >>     }
> >>     free(sbs);
> >> 
> >> which means that wt-status.c is leaking not only 'split', but also
> >> each element of split[], right?
> >
> > Yeah, I didn't notice that, but I think you're right.
> 
> Correct.
> 
> I suspect that we would be better off in the longer term if
> we made conscious effort to deprecate and eradicate the use
> of strbuf_split* API functions.  They are easy to write
> crappy code with, inefficient, and error prone.  You would
> rarely need to have N resulting pieces as strbufs to be
> easily manipulatable [*1*].

Yeah, I agree that it is a clunky interface, and I would be happy to see it go away. Many callers would be better off with string_list_split(). When I've looked in the past, though, converting some of the callers was somewhat non-trivial.

But in this case...

> The function can be written by not using the "split and then
> rebuild" pattern, perhaps like so, and the result is even
> easier to read and understand, I would say.  A sample rewrite
> is attached at the end.

I agree that the function is much simpler without it.

Show 8 quoted lines

> +	/* find the second token on the line */
> +	cp = strchr(line->buf, ' ');
> +	if (!cp)
> +		return;
> +	cp++;
> +	ep = strchr(cp, ' ');
> +	if (!ep)
> +		return;

Would we ever see "cmd sha1" without a third token? If so, we'd want:

  ep = strchrnul(cp, ' ');

-Peff