Re: [PATCH v2 4/6] log: fix common "rev.pending" memory leak in "git show"
- From
Jeff King <peff@peff.net>
- Date
- Jul 29, 2022, 19:07 UTC
- Message-ID
- <YuQv7T11VSj0EDSA@coredump.intra.peff.net>
- In-Reply-To
- <YuQtJ2DxNKX/y70N@coredump.intra.peff.net>
On Fri, Jul 29, 2022 at 02:55:35PM -0400, Jeff King wrote:
Show 20 quoted lines
> > @@ -744,7 +745,6 @@ int cmd_show(int argc, const char **argv, const char *prefix) > > rev.shown_one = 1; > > break; > > case OBJ_COMMIT: > > - memcpy(&rev.pending, &blank, sizeof(rev.pending)); > > add_object_array(o, name, &rev.pending); > > ret = cmd_log_walk_no_free(&rev); > > break; > > We now do not do anything to clean up rev.pending. On the first pass, > we'd see our blank pending array and add to it. But on a subsequent pass > (i.e., because we are showing two or more commits), what will we see? > > My initial assumption was we'd have the last pass's commit in "pending" > here, so we'd be leaking it. But I think in practice it's OK. We end up > in prepare_revision_walk(), which blanks the list again, and then > processes each element. Non-commits _do_ end up back in the pending > list, which would be a leak. But we know that this code triggers only > for commits, which are placed only in the "commits" list (and that's > cleaned up as we walk it via get_revision()).
Sorry, just one more clarification here.
The "so we'd be leaking it" in the second paragraph is really: so before this patch, we'd have been leaking it writing over it with blank. After this patch, we'd be building up an ever-growing list of pending objects, and showing a quadratic number of entries. ;)
-Peff