[v2,03/10] commit-graph: consolidate fill_commit_graph_info

Commit Message

Philippe Blain via GitGitGadget Aug. 9, 2020, 2:53 a.m. UTC

From: Abhishek Kumar <[e-mail]>

Both fill_commit_graph_info() and fill_commit_in_graph() parse
information present in commit data chunk. Let's simplify the
implementation by calling fill_commit_graph_info() within
fill_commit_in_graph().

The test 'generate tar with future mtime' creates a commit with commit
time of (2 ^ 36 + 1) seconds since EPOCH. The commit time overflows into
generation number (within CDAT chunk) and has undefined behavior.

The test used to pass as fill_commit_in_graph() guarantees the values of
graph position and generation number, and did not load timestamp.
However, with corrected commit date we will need load the timestamp as
well to populate the generation number.

Let's fix the test by setting a timestamp of (2 ^ 34 - 1) seconds.

Signed-off-by: Abhishek Kumar <[e-mail]>
---
 commit-graph.c      | 29 +++++++++++------------------
 t/t5000-tar-tree.sh |  4 ++--
 2 files changed, 13 insertions(+), 20 deletions(-)

Patch

diff --git a/commit-graph.c b/commit-graph.c
index ace7400a1a..af8d9cc45e 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -725,15 +725,24 @@  static void fill_commit_graph_info(struct commit *item, struct commit_graph *g,
 	const unsigned char *commit_data;
 	struct commit_graph_data *graph_data;
 	uint32_t lex_index;
+	uint64_t date_high, date_low;
 
 	while (pos < g->num_commits_in_base)
 		g = g->base_graph;
 
+	if (pos >= g->num_commits + g->num_commits_in_base)
+		die(_("invalid commit position. commit-graph is likely corrupt"));
+
 	lex_index = pos - g->num_commits_in_base;
 	commit_data = g->chunk_commit_data + GRAPH_DATA_WIDTH * lex_index;
 
 	graph_data = commit_graph_data_at(item);
 	graph_data->graph_pos = pos;
+
+	date_high = get_be32(commit_data + g->hash_len + 8) & 0x3;
+	date_low = get_be32(commit_data + g->hash_len + 12);
+	item->date = (timestamp_t)((date_high << 32) | date_low);
+
 	graph_data->generation = get_be32(commit_data + g->hash_len + 8) >> 2;
 }
 
@@ -748,38 +757,22 @@  static int fill_commit_in_graph(struct repository *r,
 {
 	uint32_t edge_value;
 	uint32_t *parent_data_ptr;
-	uint64_t date_low, date_high;
 	struct commit_list **pptr;
-	struct commit_graph_data *graph_data;
 	const unsigned char *commit_data;
 	uint32_t lex_index;
 
 	while (pos < g->num_commits_in_base)
 		g = g->base_graph;
 
-	if (pos >= g->num_commits + g->num_commits_in_base)
-		die(_("invalid commit position. commit-graph is likely corrupt"));
+	fill_commit_graph_info(item, g, pos);
 
-	/*
-	 * Store the "full" position, but then use the
-	 * "local" position for the rest of the calculation.
-	 */
-	graph_data = commit_graph_data_at(item);
-	graph_data->graph_pos = pos;
 	lex_index = pos - g->num_commits_in_base;
-
-	commit_data = g->chunk_commit_data + (g->hash_len + 16) * lex_index;
+	commit_data = g->chunk_commit_data + GRAPH_DATA_WIDTH * lex_index;
 
 	item->object.parsed = 1;
 
 	set_commit_tree(item, NULL);
 
-	date_high = get_be32(commit_data + g->hash_len + 8) & 0x3;
-	date_low = get_be32(commit_data + g->hash_len + 12);
-	item->date = (timestamp_t)((date_high << 32) | date_low);
-
-	graph_data->generation = get_be32(commit_data + g->hash_len + 8) >> 2;
-
 	pptr = &item->parents;
 
 	edge_value = get_be32(commit_data + g->hash_len);
diff --git a/t/t5000-tar-tree.sh b/t/t5000-tar-tree.sh
index 37655a237c..1986354fc3 100755
--- a/t/t5000-tar-tree.sh
+++ b/t/t5000-tar-tree.sh
@@ -406,7 +406,7 @@  test_expect_success TIME_IS_64BIT 'set up repository with far-future commit' '
 	rm -f .git/index &&
 	echo content >file &&
 	git add file &&
-	GIT_COMMITTER_DATE="@68719476737 +0000" \
+	GIT_COMMITTER_DATE="@17179869183 +0000" \
 		git commit -m "tempori parendum"
 '
 
@@ -415,7 +415,7 @@  test_expect_success TIME_IS_64BIT 'generate tar with future mtime' '
 '
 
 test_expect_success TAR_HUGE,TIME_IS_64BIT,TIME_T_IS_64BIT 'system tar can read our future mtime' '
-	echo 4147 >expect &&
+	echo 2514 >expect &&
 	tar_info future.tar | cut -d" " -f2 >actual &&
 	test_cmp expect actual
 '