[PATCH v2 0/1] Properly peel tags in can_all_from_reach_with_flags()

From: Derrick Stolee via GitGitGadget <gitgitgadget@gmail.com>
Date: Sep 13, 2018, 16:10 UTC
Message-ID: <pull.39.v2.git.gitgitgadget@gmail.com>
In-Reply-To: <pull.39.git.gitgitgadget@gmail.com>

As Peff reported [1], the refactored can_all_from_reach_with_flags() method does not properly peel tags. Since the helper method can_all_from_reach() and code in t/helper/test-reach.c all peel tags before getting to this method, it is not super-simple to create a test that demonstrates this.

I modified t/helper/test-reach.c to allow calling can_all_from_reach_with_flags() directly, and added a test in t6600-test-reach.sh that demonstrates the segfault without the fix.

For V2, I compared the loop that inspects the 'from' commits in commit ba3ca1edce "commit-reach: move can_all_from_reach_with_flags" to the version here and got the following diff:

3c3 < if (from_one->flags & assign_flag) ---

>                 if (!from_one || from_one->flags & assign_flag)

5c5,7 < from_one = deref_tag(the_repository, from_one, "a from object", 0); ---

>
>                 from_one = deref_tag(the_repository, from_one,
>                                      "a from object", 0);

14a17,22

Show 6 quoted lines

>
>                 list[nr_commits] = (struct commit *)from_one;
>                 if (parse_commit(list[nr_commits]) ||
>                     list[nr_commits]->generation < min_generation)
>                         return 0; /* is this a leak? */
>                 nr_commits++;

This diff includes the early termination we had before 'deref_tag' and the comment for why we can ignore non-commit objects.

[1] https://public-inbox.org/git/0bf9103c-9377-506b-7ad7-e5273d8e94fc@gmail.com/T/#u

Derrick Stolee (1):
  commit-reach: properly peel tags

 commit-reach.c        | 33 ++++++++++++++++++++++++++-------
 t/helper/test-reach.c | 22 +++++++++++++++++-----
 t/t6600-test-reach.sh | 30 ++++++++++++++++++++++++++++--
 3 files changed, 71 insertions(+), 14 deletions(-)

base-commit: 6621c838743812aaba96e55cfec8524ea1144c2d
Published-As: https://github.com/gitgitgadget/git/releases/tags/pr-39%2Fderrickstolee%2Ftag-fix-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-39/derrickstolee/tag-fix-v2
Pull-Request: https://github.com/gitgitgadget/git/pull/39

Range-diff vs v1:

 1:  948e222228 ! 1:  4bf21204dd commit-reach: properly peel tags
     @@ -36,9 +36,17 @@
      -		if (parse_commit(list[i]) ||
      -		    list[i]->generation < min_generation)
      -			return 0;
     ++		if (!from_one || from_one->flags & assign_flag)
     ++			continue;
     ++
      +		from_one = deref_tag(the_repository, from_one,
      +				     "a from object", 0);
      +		if (!from_one || from_one->type != OBJ_COMMIT) {
     ++			/* no way to tell if this is reachable by
     ++			 * looking at the ancestry chain alone, so
     ++			 * leave a note to ourselves not to worry about
     ++			 * this object anymore.
     ++			 */
      +			from->objects[i].item->flags |= assign_flag;
      +			continue;
      +		}
     @@ -187,7 +195,7 @@
      +	echo "can_all_from_reach_with_flag(X,_,_,0,0):1" >expect &&
      +	test_three_modes can_all_from_reach_with_flag
      +'
     -+	
     ++
       test_expect_success 'commit_contains:hit' '
       	cat >input <<-\EOF &&
       	A:commit-7-7

-- 
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