Re: [PATCH] prune: save reachable-from-recent objects with bitmaps

From: Jeff King <peff@peff.net>
Date: Apr 28, 2021, 15:13 UTC
Message-ID: <YIl7tUJA6sQe2K73@coredump.intra.peff.net>
In-Reply-To: <CAJ-dYSOHEfRq3p_MQMJoHf5PjwQtbJOzJ9Dzxrfe+BDkov7Q8w@mail.gmail.com>

On Wed, Apr 28, 2021 at 01:20:03PM +0100, David Emett wrote:

Show 9 quoted lines

> > Here's a fix. Thanks very much for reporting.
> 
> Thanks for the quick response! I tried the fix out on the repo I was having
> trouble with. It's hitting a segfault in traverse_commit_list in the
> mark_recent block. It looks like the issue is that the bitmap code leaves
> revs->include_check set, with revs->include_check_data pointing at the stack.
> Setting revs->include_check to NULL after the traverse_commit_list call in
> find_objects in pack-bitmap.c fixes the segfault for me. And the original issue
> appears to be resolved as well, so thanks!

Oof, good catch. I wondered why my test didn't see this. The answer is that the include_check only applies to commits, not trees. And my test only has a recent-but-unreachable tree. Beefing it up to include an actual commit shows the problem (and ASan nicely pinpoints the issue).

The solution, as you noted, is to have the bitmap code clean up after itself.

I'll prepare a re-roll of the series.

-Peff