[PATCH 1/1] commit-graph: writing missing parents is a BUG
- From
Derrick Stolee via GitGitGadget <gitgitgadget@gmail.com>
- Date
- Dec 19, 2018, 20:14 UTC
- Message-ID
- <907a24d2c45acec17607971b577782798c4adcbc.1545250444.git.gitgitgadget@gmail.com>
- In-Reply-To
- <pull.102.git.gitgitgadget@gmail.com>
From: Derrick Stolee <dstolee@microsoft.com>
When writing a commit-graph, we write GRAPH_MISSING_PARENT if the parent's object id does not appear in the list of commits to be written into the commit-graph. This was done as the initial design allowed commits to have missing parents, but the final version requires the commit-graph to be closed under reachability. Thus, this GRAPH_MISSING_PARENT value should never be written.
However, there are reasons why it could be written! These range from a bug in the reachable-closure code to a memory error causing the binary search into the list of object ids to fail. In either case, we should fail fast and avoid writing the commit-graph file with bad data.
Remove the GRAPH_MISSING_PARENT constant in favor of the constant GRAPH_EDGE_LAST_MASK, which has the same value.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com> --- commit-graph.c | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-)
diff --git a/commit-graph.c b/commit-graph.c index 40c855f185..c14ada6918 100644 --- a/commit-graph.c +++ b/commit-graph.c @@ -34,7 +34,6 @@ #define GRAPH_OID_LEN GRAPH_OID_LEN_SHA1 #define GRAPH_OCTOPUS_EDGES_NEEDED 0x80000000 -#define GRAPH_PARENT_MISSING 0x7fffffff #define GRAPH_EDGE_LAST_MASK 0x7fffffff #define GRAPH_PARENT_NONE 0x70000000 @@ -496,7 +495,9 @@ static void write_graph_chunk_data(struct hashfile *f, int hash_len, commit_to_sha1); if (edge_value < 0) - edge_value = GRAPH_PARENT_MISSING; + BUG("missing parent %s for commit %s", + oid_to_hex(&parent->item->object.oid), + oid_to_hex(&(*list)->object.oid)); } hashwrite_be32(f, edge_value); @@ -514,7 +515,9 @@ static void write_graph_chunk_data(struct hashfile *f, int hash_len, nr_commits, commit_to_sha1); if (edge_value < 0) - edge_value = GRAPH_PARENT_MISSING; + BUG("missing parent %s for commit %s", + oid_to_hex(&parent->item->object.oid), + oid_to_hex(&(*list)->object.oid)); } hashwrite_be32(f, edge_value); @@ -567,7 +570,9 @@ static void write_graph_chunk_large_edges(struct hashfile *f, commit_to_sha1); if (edge_value < 0) - edge_value = GRAPH_PARENT_MISSING; + BUG("missing parent %s for commit %s", + oid_to_hex(&parent->item->object.oid), + oid_to_hex(&(*list)->object.oid)); else if (!parent->next) edge_value |= GRAPH_LAST_EDGE; @@ -864,7 +869,7 @@ void write_commit_graph(const char *obj_dir, count_distinct++; } - if (count_distinct >= GRAPH_PARENT_MISSING) + if (count_distinct >= GRAPH_EDGE_LAST_MASK) die(_("the commit graph format cannot write %d commits"), count_distinct); commits.nr = 0; @@ -891,7 +896,7 @@ void write_commit_graph(const char *obj_dir, } num_chunks = num_extra_edges ? 4 : 3; - if (commits.nr >= GRAPH_PARENT_MISSING) + if (commits.nr >= GRAPH_EDGE_LAST_MASK) die(_("too many commits to write graph")); compute_generation_numbers(&commits, report_progress);
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