Jeff KingIn verify_one_commit_graph(), we have code that complains when a commit is found with a generation number of zero, and then later with a non-zero number. It works like this:
1. When we see an entry with generation zero, we set the
generation_zero flag to GENERATION_ZERO_EXISTS. 2. When we later see an entry with a non-zero generation, we complain
if the flag is GENERATION_ZERO_EXISTS.There's a matching GENERATION_NUMBER_EXISTS value, which in theory would be used to find the case that we see the entries in the opposite order:
1. When we see an entry with a non-zero generation, we set the
generation_zero flag to GENERATION_NUMBER_EXISTS. 2. When we later see an entry with a zero generation, we complain if
the flag is GENERATION_NUMBER_EXISTS.But that doesn't work; step 2 is implemented, but there is no step 1. We never use NUMBER_EXISTS at all, and Coverity rightly complains that step 2 is dead code.
We can fix that by implementing that step 1.
Signed-off-by: Jeff King <peff@peff.net> --- This is marked as RFC because I'm still confused about a lot of things. For one, my explanation above about what the code is doing is mostly a guess. It _looks_ to me like that's what the existing check is trying to do. But if so, then why is the generation_zero flag defined outside the loop over each object? I'd think it would be a per-object thing.
Likewise, just below this code, we check:
if (generation_zero == GENERATION_ZERO_EXISTS)
continue;Is the intent here "if this is the zero-th generation, we can skip the rest of the loop because there are no more parents to look at"? If so, then would it make more sense to check commit_graph_generation() directly? I took care to preserve the existing behavior by pushing the set of NUMBER_EXISTS into an "else", but it seems like a weird use of the flag to me.
So I kind of wonder if there's something I'm not getting here. Coverity is definitely right that our "step 2" is dead code (because we never set NUMBER_EXISTS). But I'm not sure if we should be deleting it, or trying to fix an underlying bug.
commit-graph.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
Show changes to commit-graph.c +6 −2
diff --git a/commit-graph.c b/commit-graph.c index 0aa1640d15..40cd55eb15 100644 --- a/commit-graph.c +++ b/commit-graph.c @@ -2676,9 +2676,13 @@ static int verify_one_commit_graph(struct repository *r, graph_report(_("commit-graph has generation number zero for commit %s, but non-zero elsewhere"), oid_to_hex(&cur_oid)); generation_zero = GENERATION_ZERO_EXISTS; - } else if (generation_zero == GENERATION_ZERO_EXISTS) - graph_report(_("commit-graph has non-zero generation number for commit %s, but zero elsewhere"), + } else { + if (generation_zero == GENERATION_ZERO_EXISTS) + graph_report(_("commit-graph has non-zero generation number for commit %s, but zero elsewhere"), oid_to_hex(&cur_oid)); + else + generation_zero = GENERATION_NUMBER_EXISTS; + } if (generation_zero == GENERATION_ZERO_EXISTS) continue;
-- 2.42.0.rc0.376.g66bfc4f195
