Re: Segfault in master due to 4fbcca4eff

[Derrick Stolee <stolee@gmail.com>]

On 9/21/2018 10:30 AM, Ævar Arnfjörð Bjarmason wrote:
> On Fri, Sep 21 2018, Junio C Hamano wrote:
>
>> * ds/reachable (2018-08-28) 19 commits
>>    (merged to 'next' on 2018-08-28 at b1634b371d)
>>   + commit-reach: correct accidental #include of C file
>>    (merged to 'next' on 2018-08-22 at 17f3275afb)
>>   + commit-reach: use can_all_from_reach
>>   + commit-reach: make can_all_from_reach... linear
>>   + commit-reach: replace ref_newer logic
>>   + test-reach: test commit_contains
>>   + test-reach: test can_all_from_reach_with_flags
>>   + test-reach: test reduce_heads
>>   + test-reach: test get_merge_bases_many
>>   + test-reach: test is_descendant_of
>>   + test-reach: test in_merge_bases
>>   + test-reach: create new test tool for ref_newer
>>   + commit-reach: move can_all_from_reach_with_flags
>>   + upload-pack: generalize commit date cutoff
>>   + upload-pack: refactor ok_to_give_up()
>>   + upload-pack: make reachable() more generic
>>   + commit-reach: move commit_contains from ref-filter
>>   + commit-reach: move ref_newer from remote.c
>>   + commit.h: remove method declarations
>>   + commit-reach: move walk methods from commit.c
>>
>>   The code for computing history reachability has been shuffled,
>>   obtained a bunch of new tests to cover them, and then being
>>   improved.
> There's a segfault now in master when fetching because of 4fbcca4eff
> ("commit-reach: make can_all_from_reach... linear", 2018-07-20). I have
> not had time to debug this, or found an easy isolated test case, but
> this script will reliably make it segfault for me:
>
>      #!/bin/sh
>
>      git_dot_git=/home/avar/g/git
>
>      old=v0.99
>      new=v0.99.1
>
>      rm -rf /tmp/srv
>      rm -rf /tmp/cln
>      git init --bare /tmp/srv
>      git init --bare /tmp/cln
>      $git_dot_git/git --exec-path=$git_dot_git push file:///tmp/srv $old:refs/whatever/ref
>      $git_dot_git/git --exec-path=$git_dot_git -C /tmp/cln fetch file:///tmp/srv 'refs/*:refs/*'
>      $git_dot_git/git --exec-path=$git_dot_git push file:///tmp/srv $new:refs/whatever/ref
>      if GIT_TRACE=1 $git_dot_git/git --exec-path=$git_dot_git -C /tmp/cln fetch file:///tmp/srv 'refs/*:refs/*'
>      then
>          exit 0
>      else
>          exit 1
>      fi
>
> I.e. you need to push the v0.99 tag to its own repo, fetch that from
> another one, then push v0.99.1, fetch everything, and you'll get a
> segfault:
>
>      remote: Resolving deltas: 100% (187/187), completed with 48 local objects.
>      To file:///tmp/srv
>         d6602ec519..f25a265a34  v0.99.1 -> refs/whatever/ref
>      14:26:44.505787 git.c:415               trace: built-in: git fetch file:///tmp/srv 'refs/*:refs/*'
>      14:26:44.506708 run-command.c:637       trace: run_command: unset GIT_DIR GIT_IMPLICIT_WORK_TREE GIT_PREFIX; 'git-upload-pack '\''/tmp/srv'\'''
>      14:26:44.508831 git.c:415               trace: built-in: git upload-pack /tmp/srv
>      14:26:44.509953 run-command.c:637       trace: run_command: git rev-list --objects --stdin --not --all --quiet
>      Segmentation fault
>      fatal: The remote end hung up unexpectedly
>
> Same with refs/tags/ref b.t.w., not just refs/whatever/ref, I just was
> initially testing this for some follow-up work on my series for checking
> how fetching to various non-heads/tags namespaces works.

This error was reported by Peff [1] and fixed in [2], but as stated [3] 
I was waiting for more review before sending a v3. I'll send that v3 
shortly, responding to the feedback so far.

-Stolee

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

[2] https://public-inbox.org/git/pull.39.git.gitgitgadget@gmail.com/

[3] 
https://public-inbox.org/git/8d6061de-1654-577c-40c6-211dbd03aa36@gmail.com/