From: Junio C Hamano <gitster@pobox.com>
To: Jeff King <peff@peff.net>
Cc: git@vger.kernel.org
Subject: Re: [PATCH 2/2] format-patch: free elements of rev.ref_message_ids list
Date: Thu, 18 May 2023 18:32:14 -0700 [thread overview]
Message-ID: <xmqqttw9qf6p.fsf@gitster.g> (raw)
In-Reply-To: <20230519000543.GB1975194@coredump.intra.peff.net> (Jeff King's message of "Thu, 18 May 2023 20:05:43 -0400")
Jeff King <peff@peff.net> writes:
> When we are showing multiple patches with format-patch, we have to
> repeatedly overwrite the rev.message_id field. We take care to avoid
> leaking the old value by either freeing it, or adding it to
> ref_message_ids, a string list of ids to reference in subsequent
> messages.
>
> But unfortunately we do leak the value via that string list. We try
> to clear the string list, courtesy of 89f45cf4eb (format-patch: don't
> leak "extra_headers" or "ref_message_ids", 2022-04-13). But since it was
> initialized as "nodup", the string list doesn't realize it owns the
> strings, and it leaks them.
>
> We have two options here:
>
> 1. Continue to init with "nodup", but then tweak the value of
> ref_message_ids.strdup_strings just before clearing.
>
> 2. Init with "dup", but use "append_nodup" when transferring ownership
> of strings to the list. Clearing just works.
>
> I picked the second here, as I think it calls attention to the tricky
> part (transferring ownership via the nodup call).
This is pretty much what I had in mind wheh I wrote the log message
for the follow-up "Yikes, for now let's mark the test no longer
sanitizer clean" patch. Very pleased to see a clean-up I punted
materialize while I was looking the other way ;-)
> There's one other related fix we have to do, though. We also insert the
> result of clean_message_id() into the list. This _sometimes_ allocates
> and sometimes does not, depending on whether we have to remove cruft
> from the end of the string. Let's teach it to consistently return an
> allocated string, so that the caller knows it must be freed.
Yes!
Thanks.
next prev parent reply other threads:[~2023-05-19 1:32 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-19 0:02 [PATCH 0/2] a few format-patch leak fixes Jeff King
2023-05-19 0:03 ` [PATCH 1/2] format-patch: free rev.message_id when exiting Jeff King
2023-05-19 0:05 ` [PATCH 2/2] format-patch: free elements of rev.ref_message_ids list Jeff King
2023-05-19 1:32 ` Junio C Hamano [this message]
2023-05-19 14:54 ` Konstantin Khomoutov
2023-05-19 16:56 ` Junio C Hamano
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