Re: [BUG] v2.16.0-rc0 seg faults when git bisect skip

["Martin Ågren" <martin.agren@gmail.com>]

> On Fri, Jan 5, 2018 at 11:45 AM, Yasushi SHOJI <yasushi.shoji@gmail.com> wrote:
>> When does the list allowed to contain NULLs?

Short answer: there are no commits left to test.

The list is built in the for-loop in `find_bisection()`. So the
technical answer is: if all commits in the initial list `commit_list`
are UNINTERESTING (including if `commit_list` is empty to begin with).

It's also helpful to study where we should end up from there. We should
take the `if (!revs.commits)` branch in `bisect_next_all()`. That is, we
should print either "There are only 'skip'ped commits left to test. The
first bad commit could be any of:" or "<commit> was both good and bad".

>> Since nobody noticed it since 7c117184d7, it must be a rare case, right?

Right, you marked a commit both good and bad. That's probably not very
common. But it obviously happens. :-)

On 5 January 2018 at 06:28, Yasushi SHOJI <yasushi.shoji@gmail.com> wrote:
> OK, here is the step to reproduce on git.git

Thank you for providing a script for reproducing this. It helped me come
up with the attached patch. The patch is based on ma/bisect-leakfix,
which includes Ævar's patch.

I think this patch could be useful, either as a final "let's test
something previously non-tested; this would have caught the segfault",
or simply squashed into Ævar's patch as a "let's add a test that would
have caught this, and which also tests a previously non-tested code
path."

Thanks for digging and finding a reproduction recipe.

Martin

-- >8 --
Subject: [PATCH] bisect: add test for marking commit both good and bad

Since 670f5fe34f ([PATCH] Fix bisection terminating condition,
2005-08-30), we have noticed and complained when a commit was marked
both good and bad. But we had no tests for this behavior.

Test the behavior when we mark a commit first bad, then good, but also
when we are already in the bad state, where `git bisect skip` should
notice it.

This test would have caught the segfault which was recently fixed in
2e9fdc795c (bisect: fix a regression causing a segfault, 2018-01-03).

Signed-off-by: Martin Ågren <martin.agren@gmail.com>
---
 t/t6030-bisect-porcelain.sh | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/t/t6030-bisect-porcelain.sh b/t/t6030-bisect-porcelain.sh
index 8c2c6eaef8..190f0ce0ab 100755
--- a/t/t6030-bisect-porcelain.sh
+++ b/t/t6030-bisect-porcelain.sh
@@ -894,4 +894,13 @@ test_expect_success 'bisect start takes options and revs in any order' '
 	test_cmp expected actual
 '
 
+test_expect_success 'marking commit both good and bad gets reported' '
+	git bisect reset &&
+	git bisect start HEAD &&
+	test_must_fail git bisect good HEAD >out &&
+	test_i18ngrep "both good and bad" out &&
+	test_must_fail git bisect skip >out &&
+	test_i18ngrep "both good and bad" out
+'
+
 test_done
-- 
2.16.0.rc1