On Fri, Dec 11 2020, Elijah Newren via GitGitGadget wrote: > While creating the last commit, I found a number of other cases where > git would segfault when faced with trees that have duplicate entries. > None of these segfaults are in the diffcore-rename code (they all occur > in cache-tree and unpack-trees). Further, to my knowledge, no one has > ever been adversely affected by these bugs, and given that it has been > 15 years and folks have fixed a few other issues with historical > duplicate entries (as noted in the last commit), I am not sure we will > ever run into anyone having problems with these. So I am not sure these > are worth fixing, but it doesn't hurt to at least document these > failures in the same test file that is concerned with duplicate tree > entries. > [...] > +test_expect_failure 'fast-forward from duplicate entries to non-duplicate' ' > + git merge update > +' > + > test_done Per https://lore.kernel.org/git/87lf9b3mth.fsf@xxxxxxxxxxxxxxxxxxx/ isn't the noise of having a segfault from "git" worth fixing in itself though? I.e. something like this, so we at least se why it fails: diff --git a/t/t4058-diff-duplicates.sh b/t/t4058-diff-duplicates.sh index 54614b814db..ed91d9f7fe9 100755 --- a/t/t4058-diff-duplicates.sh +++ b/t/t4058-diff-duplicates.sh @@ -182,8 +182,10 @@ test_expect_success 'switch to base branch and force status to be clean' ' test_must_be_empty actual ' -test_expect_failure 'fast-forward from duplicate entries to non-duplicate' ' - git merge update +test_expect_success 'fast-forward from duplicate entries to non-duplicate' ' + ! git merge update 2>err && + grep "^BUG: " err && + grep -F "should have entry at o->src_index->cache[1]" err ' test_done diff --git a/unpack-trees.c b/unpack-trees.c index 8a1afbc1e49..230cb073fe1 100644 --- a/unpack-trees.c +++ b/unpack-trees.c @@ -789,8 +789,11 @@ static int traverse_by_cache_tree(int pos, int nr_entries, int nr_names, */ for (i = 0; i < nr_entries; i++) { int new_ce_len, len, rc; + int j = pos + i; - src[0] = o->src_index->cache[pos + i]; + src[0] = o->src_index->cache[j]; + if (!src[0]) + BUG("should have entry at o->src_index->cache[%d]", j); len = ce_namelen(src[0]); new_ce_len = cache_entry_size(len);
