Re: [PATCH v2 2/4] mktree: plug per-tree leak in --batch mode

From: Jeff King <peff@peff.net>
Date: Aug 27, 2026, 05:36 UTC
Message-ID: <20260827053602.GA189659@coredump.intra.peff.net>
In-Reply-To: <3f3b75690eea02960c7edc8d318ce7dff654f1bc.1787684429.git.gitgitgadget@gmail.com>

On Tue, Aug 25, 2026 at 07:00:27PM +0000, Elijah Newren via GitGitGadget wrote:

Show 9 quoted lines

> In --batch mode "git mktree" reuses its entry buffer across trees,
> resetting `used` to 0 after writing each tree.  It never frees the
> `treeent` structures the previous tree appended, though, so once the
> next tree overwrites those slots the earlier allocations are leaked.  A
> single-tree invocation hides this, as the entries stay reachable through
> the `entries` global until exit.
> 
> Free each entry when resetting the buffer, and free the buffer itself
> before returning.

Yikes. It is sad that we did not catch this in our leak-checking builds, as it implies that we do not test "mktree --batch" with multiple inputs. Or grepping for "mktree.*--batch" implies that we do not test the feature at all!

Looks like that feature comes from f1cf2d8b14 (mktree --batch: build more than one tree object, 2009-05-14), so I am not surprised that test coverage was a bit more spotty back then.

I guess you are going to add some coverage incidentally (or else you would not have found this). That's better than nothing, but I suspect a few basic directed "mktree --batch" tests would be a good thing to have in t1010.

#leftoverbits, perhaps?

-Peff