Re: [PATCH] revision: fix memory leak in prepare_show_merge()

From: lidongyan <502024330056@smail.nju.edu.cn>
Date: Jun 9, 2025, 03:10 UTC
Message-ID: <32D22FB7-F6C4-408B-A3AE-AF780FA16C0E@smail.nju.edu.cn>
In-Reply-To: <xmqqikl83jhl.fsf@gitster.g>

2025年6月7日 00:47，Junio C Hamano <gitster@pobox.com> 写道：

Show 12 quoted lines

> 
> lidongyan <502024330056@smail.nju.edu.cn> writes:
> 
>> I could add this test case into my patch. Though I don’t understand
>>> + git rev-parse HEAD >.git/MERGE_HEAD &&
> 
> That was not about telling "show --merge" to work on any meaningful
> data and to produce any useful output.  I knew the step to prepare
> for "show --merge" was leaky, so I gave a very minimum that can tickle
> that codepath.  I wasn't of course proud of the direct manipulation
> of the filesystem (as recent "git update-ref MERGE_HEAD HEAD" would
> not even allow us to do this, sheesh, not very convenient).

I understand. `show —merge` means the codepath must go through prepare_show_merge() And `update-index` with index which has stage greater than 0 let prepare_show_merge() go through loop and add index to prune. Thus cause a leak.

Show 42 quoted lines

> 
> If you came up with a sequence that produces a situation to use the
> "git show --merge" command in a more realistic way, like below, that
> is wonderful.
> 
>> If HEAD is equal to MERGE_HEAD. Would git show —merge still
>> works as usual? How about something like this
>> 
>> diff --git a/t/t7007-show.sh b/t/t7007-show.sh
>> index d6cc69e0f2..f693b6e24b 100755
>> --- a/t/t7007-show.sh
>> +++ b/t/t7007-show.sh
>> @@ -167,4 +167,28 @@ test_expect_success 'show --graph is forbidden' '
>>   test_must_fail git show --graph HEAD
>> '
>> 
>> +test_expect_success 'unmerged index' '
>> +       git reset --hard &&
>> +
>> +       git switch -C base &&
>> +       echo "base" > conflicting &&
>> +       git add conflicting &&
>> +       git commit -m "base" &&
>> +
>> +       git branch hello &&
>> +       git branch goodbye &&
>> +
>> +       git switch hello &&
>> +       echo "hello" > conflicting &&
>> +       git commit -am "hello" &&
>> +
>> +       git switch goodbye &&
>> +       echo "goodbye" > conflicting &&
>> +       git commit -am "goodbye" &&
>> +
>> +       git switch hello &&
>> +       test_must_fail git merge goodbye &&
>> +       git show --merge HEAD
>> +'
>> +
>> test_done
>