From 2ec4150713eabc725ba1c43fbe032adb43d5d4cf Mon Sep 17 00:00:00 2001 From: Jeff King Date: Thu, 2 Aug 2018 14:58:21 -0400 Subject: score_trees(): fix iteration over trees with missing entries MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit In score_trees(), we walk over two sorted trees to find which entries are missing or have different content between the two. So if we have two trees with these entries: one two --- --- a a b c c d we'd expect the loop to: - compare "a" to "a" - compare "b" to "c"; because these are sorted lists, we know that the second tree does not have "b" - compare "c" to "c" - compare "d" to end-of-list; we know that the first tree does not have "d" And prior to d8febde370 (match-trees: simplify score_trees() using tree_entry(), 2013-03-24) that worked. But after that commit, we mistakenly increment the tree pointers for every loop iteration, even when we've processed the entry for only one side. As a result, we end up doing this: - compare "a" to "a" - compare "b" to "c"; we know that we do not have "b", but we still increment both tree pointers; at this point we're out of sync and all further comparisons are wrong - compare "c" to "d" and mistakenly claim that the second tree does not have "c" - exit the loop, mistakenly not realizing that the first tree does not have "d" So contrary to the claim in d8febde370, we really do need to manually use update_tree_entry(), because advancing the tree pointer depends on the entry comparison. That means we must stop using tree_entry() to access each entry, since it auto-advances the pointer. Instead: - we'll use tree_desc.size directly to know if there's anything left to look at (which is what tree_entry() was doing under the hood) - rather than do an extra struct assignment to "e1" and "e2", we can just access the "entry" field of tree_desc directly That makes us a little more intimate with the tree_desc code, but that's not uncommon for its callers. The included test shows off the bug by adding a new entry "bar.t", which sorts early in the tree and de-syncs the comparison for "foo.t", which comes after. Reported-by: George Shammas Helped-by: René Scharfe Signed-off-by: Jeff King Signed-off-by: Junio C Hamano --- match-trees.c | 43 ++++++++++++++++++++++++++----------------- 1 file changed, 26 insertions(+), 17 deletions(-) (limited to 'match-trees.c') diff --git a/match-trees.c b/match-trees.c index 396b7338df..ad9e5e9744 100644 --- a/match-trees.c +++ b/match-trees.c @@ -82,34 +82,43 @@ static int score_trees(const struct object_id *hash1, const struct object_id *ha int score = 0; for (;;) { - struct name_entry e1, e2; - int got_entry_from_one = tree_entry(&one, &e1); - int got_entry_from_two = tree_entry(&two, &e2); int cmp; - if (got_entry_from_one && got_entry_from_two) - cmp = base_name_entries_compare(&e1, &e2); - else if (got_entry_from_one) + if (one.size && two.size) + cmp = base_name_entries_compare(&one.entry, &two.entry); + else if (one.size) /* two lacks this entry */ cmp = -1; - else if (got_entry_from_two) + else if (two.size) /* two has more entries */ cmp = 1; else break; - if (cmp < 0) + if (cmp < 0) { /* path1 does not appear in two */ - score += score_missing(e1.mode, e1.path); - else if (cmp > 0) + score += score_missing(one.entry.mode, one.entry.path); + update_tree_entry(&one); + } else if (cmp > 0) { /* path2 does not appear in one */ - score += score_missing(e2.mode, e2.path); - else if (oidcmp(e1.oid, e2.oid)) - /* they are different */ - score += score_differs(e1.mode, e2.mode, e1.path); - else - /* same subtree or blob */ - score += score_matches(e1.mode, e2.mode, e1.path); + score += score_missing(two.entry.mode, two.entry.path); + update_tree_entry(&two); + } else { + /* path appears in both */ + if (oidcmp(one.entry.oid, two.entry.oid)) { + /* they are different */ + score += score_differs(one.entry.mode, + two.entry.mode, + one.entry.path); + } else { + /* same subtree or blob */ + score += score_matches(one.entry.mode, + two.entry.mode, + one.entry.path); + } + update_tree_entry(&one); + update_tree_entry(&two); + } } free(one_buf); free(two_buf); -- cgit v1.2.3