Subject: Re: [PATCH 01/11] Fix memory leak in traverse_commit_list

From: "Shawn O. Pearce" <[email-masked]>
Date: Sun, 11 Nov 2007 00:17:42 -0500

Junio C Hamano <[email-masked]> wrote:
> "Shawn O. Pearce" <[email-masked]> writes:
> 
> > diff --git a/list-objects.c b/list-objects.c
> > index e5c88c2..713bef9 100644
> > --- a/list-objects.c
> > +++ b/list-objects.c
> > @@ -170,4 +170,11 @@ void traverse_commit_list(struct rev_info *revs,
> >  	}
> >  	for (i = 0; i < objects.nr; i++)
> >  		show_object(&objects.objects[i]);
> > +	free(objects.objects);
> > +	if (revs->pending.nr) {
> > +		revs->pending.nr = 0;
> > +		revs->pending.alloc = 0;
> > +		revs->pending.objects = NULL;
> > +		free(revs->pending.objects);
> > +	}
> >  }
> 
> It is locally verifiable that objects.objects are no longer
> needed after this point, but it made me a bit nervous about
> freeing of revs->pending.objects.
> 
> I think the existing callers are all Ok, but somebody else
> should double check.

There are 5 calllers:

* builtin-fetch.c:

   This one I added with my series.  It doesn't care about the
   pending object list.

* builtin-pack-objects.c:

   This doesn't care about the pending list after the call to
   traverse_commit_list.

* builtin-rev-list.c (2):

   Two calls; the first one is for the bisect case where we print
   bisect stats and then return 0 and the second is the end of
   the program for the non-bisect case.  Neither cares about the
   pending list.

* upload-pack.c:

   This is called in the async thread spawned by upload-pack to
   feed pack-objects.  The last thing the async thread does is run
   traverse_commit_list, at which point it exits.  I actually have
   to wonder why we didn't just teach this trick to pack-objects
   so we could avoid the async complexity here in upload-pack.

So yea, the cleanup here is safe, assuming I didn't make the
extremely obvious leak of setting to NULL then calling free()
(as Dscho pointed out).

-- 
Shawn.