From 3506dc944558b7d88544408b312e795458383195 Mon Sep 17 00:00:00 2001 From: Jeff King Date: Wed, 11 Jul 2018 10:14:06 -0400 Subject: has_uncommitted_changes(): fall back to empty tree MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit If has_uncommitted_changes() can't resolve HEAD (e.g., because it's unborn or corrupt), then we end up calling run_diff_index() with an empty revs.pending array. This causes a segfault, as run_diff_index() blindly looks at the first pending item. Fixing this raises a question of fault: should run_diff_index() handle this case, or is the caller wrong to pass an empty pending list? Looking at the other callers of run_diff_index(), they handle this in one of three ways: - they resolve the object themselves, and avoid doing the diff if it's not valid - they resolve the object themselves, and fall back to the empty tree - they use setup_revisions(), which will die() if the object isn't valid Since this is the only broken caller, that argues that the fix should go there. Falling back to the empty tree makes sense here, as we'd claim uncommitted changes if and only if the index is non-empty. This may be a little funny in the case of corruption (the corrupt HEAD probably _isn't_ empty), but: - we don't actually know the reason here that HEAD didn't resolve (the much more likely case is that we have an unborn HEAD, in which case the empty tree comparison is the right thing) - this matches how other code, like "git diff", behaves While we're thinking about it, let's add an assertion to run_diff_index(). It should always be passed a single object, and as this bug shows, it's easy to get it wrong (and an assertion is easier to hunt down than a segfault, or a quietly ignored extra tree). Reported-by: Ævar Arnfjörð Bjarmason Signed-off-by: Jeff King Signed-off-by: Junio C Hamano --- diff-lib.c | 3 +++ t/t5520-pull.sh | 12 ++++++++++++ wt-status.c | 10 ++++++++++ 3 files changed, 25 insertions(+) diff --git a/diff-lib.c b/diff-lib.c index 8104603a3b..7eea70e813 100644 --- a/diff-lib.c +++ b/diff-lib.c @@ -513,6 +513,9 @@ int run_diff_index(struct rev_info *revs, int cached) { struct object_array_entry *ent; + if (revs->pending.nr != 1) + BUG("run_diff_index must be passed exactly one tree"); + ent = revs->pending.objects; if (diff_cache(revs, &ent->item->oid, ent->name, cached)) exit(128); diff --git a/t/t5520-pull.sh b/t/t5520-pull.sh index 59c4b778d3..68aa5f0340 100755 --- a/t/t5520-pull.sh +++ b/t/t5520-pull.sh @@ -618,6 +618,18 @@ test_expect_success 'pull --rebase fails on unborn branch with staged changes' ' ) ' +test_expect_success 'pull --rebase fails on corrupt HEAD' ' + test_when_finished "rm -rf corrupt" && + git init corrupt && + ( + cd corrupt && + test_commit one && + obj=$(git rev-parse --verify HEAD | sed "s#^..#&/#") && + rm -f .git/objects/$obj && + test_must_fail git pull --rebase + ) +' + test_expect_success 'setup for detecting upstreamed changes' ' mkdir src && (cd src && diff --git a/wt-status.c b/wt-status.c index f5debcd2b4..e196567236 100644 --- a/wt-status.c +++ b/wt-status.c @@ -2315,7 +2315,17 @@ int has_uncommitted_changes(int ignore_submodules) if (ignore_submodules) rev_info.diffopt.flags.ignore_submodules = 1; rev_info.diffopt.flags.quick = 1; + add_head_to_pending(&rev_info); + if (!rev_info.pending.nr) { + /* + * We have no head (or it's corrupt); use the empty tree, + * which will complain if the index is non-empty. + */ + struct tree *tree = lookup_tree(the_hash_algo->empty_tree); + add_pending_object(&rev_info, &tree->object, ""); + } + diff_setup_done(&rev_info.diffopt); result = run_diff_index(&rev_info, 1); return diff_result_code(&rev_info.diffopt, result); -- cgit v1.2.3