Re: Assertion in git log graphing [regression in v2.25]

From: Derrick Stolee <stolee@gmail.com>
Date: Jan 7, 2020, 12:22 UTC
Message-ID: <d694a5b5-9c88-0a34-b9fd-050e5e02c312@gmail.com>
In-Reply-To: <20200107114812.GE1073219@coredump.intra.peff.net>

On 1/7/2020 6:48 AM, Jeff King wrote:

Show 22 quoted lines

> On Tue, Jan 07, 2020 at 11:24:50AM +0000, Bradley Smith wrote:
> 
>> The following git repository (https://github.com/brads55/git-testcase)
>> causes an assertion when running:
>>
>>   $ git log --oneline --graph --all
>>
>>   git-log: graph.c:1228: graph_output_collapsing_line: Assertion
>> `graph->mapping[i - 3] == target' failed.
> 
> Thanks for the report, and especially for providing a reproduction case!
> 
> The problem is new in the v2.25 release candidates, so we should try to
> deal with it before the release.
> 
>> The assertion seems to be caused by commit
>> 0f0f389f12029b1c3745f8ed7aacfe6b2fc7a6cc. The graph structure of the
>> above repository is as follows (as produced by v2.24.1):
> 
> Yeah, I can confirm that this introduces the problem. I admit to not
> following the recent graph changes too closely, so I'll add James to the
> cc for attention.

I'm also going to take a look this morning, starting by creating a test. I reviewed what I could of James' patch series, but I was also unfamiliar with graph.c and relied on his very substantial test cases to verify the correctness. Looks like a corner case got missed.

Thanks, -Stolee