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024b4c9697
In the next commit we will start to parse more commits via the
commit-graph. This change will lead to a segfault though because we try
to access the tree of a commit via `repo_get_commit_tree()`, but:
- The commit has been parsed via the commit-graph, and thus its
`maybe_tree` field is not yet populated.
- We cannot use the commit-graph to populate the commit's tree because
we're in the process of writing the commit-graph.
The consequence is that we'll get a `NULL` pointer for the tree in
`write_graph_chunk_data()`.
In theory we are already mindful of this situation, as we explicitly use
`repo_parse_commit_no_graph()` to parse the commit without the help of
the commit-graph. But that doesn't do the trick as the commit is already
marked as parsed, so the function will not re-populate it. And as the
commit-graph has been closed, neither will `get_commit_tree_oid()` be
able to load the tree for us.
It seems like this issue can only be hit under artificial circumstances:
the error was hit via `git_test_write_commit_graph_or_die()`, which is
run by git-commit(1) and git-merge(1) in case `GIT_TEST_COMMIT_GRAPH=1`:
$ GIT_TEST_COMMIT_GRAPH=1 meson test t7507-commit-verbose \
--test-args=-ix -i
...
++ git -c commit.verbose=true commit --amend
hint: Waiting for your editor to close the file...
./test-lib.sh: line 1012: 55895 Segmentation fault (core dumped) git -c commit.verbose=true commit --amend
To the best of my knowledge, this is the only case where we end up
writing a commit-graph in the same process that might have already
consulted the commit-graph to look up arbitrary objects. But regardless
of that, this feels like a bigger accident that is just waiting to
happen.
Make the code more robust by extending `repo_parse_commit_no_graph()` to
unparse a commit first in case we detect it's coming from a graph. This
ensures that we will re-read the object without it, and thus we will
populate `maybe_tree` properly.
This fix shouldn't have any performance consequences: the function is
only ever called in the "commit-graph.c" code, and we'll only re-parse
the commit at most once.
Add an exclusion to our Coccinelle rules so that it doesn't complain
about us accessing `maybe_tree` directly.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Contributed Software Although these pieces are available as part of the official git source tree, they are in somewhat different status. The intention is to keep interesting tools around git here, maybe even experimental ones, to give users an easier access to them, and to give tools wider exposure, so that they can be improved faster. I am not expecting to touch these myself that much. As far as my day-to-day operation is concerned, these subdirectories are owned by their respective primary authors. I am willing to help if users of these components and the contrib/ subtree "owners" have technical/design issues to resolve, but the initiative to fix and/or enhance things _must_ be on the side of the subtree owners. IOW, I won't be actively looking for bugs and rooms for enhancements in them as the git maintainer -- I may only do so just as one of the users when I want to scratch my own itch. If you have patches to things in contrib/ area, the patch should be first sent to the primary author, and then the primary author should ack and forward it to me (git pull request is nicer). This is the same way as how I have been treating gitk, and to a lesser degree various foreign SCM interfaces, so you know the drill. I expect things that start their life in the contrib/ area to graduate out of contrib/ once they mature, either by becoming projects on their own, or moving to the toplevel directory. On the other hand, I expect I'll be proposing removal of disused and inactive ones from time to time. If you have new things to add to this area, please first propose it on the git mailing list, and after a list discussion proves there is general interest (it does not have to be a list-wide consensus for a tool targeted to a relatively narrow audience -- for example I do not work with projects whose upstream is svn, so I have no use for git-svn myself, but it is of general interest for people who need to interoperate with SVN repositories in a way git-svn works better than git-svnimport), submit a patch to create a subdirectory of contrib/ and put your stuff there. -jc