From: Derrick Stolee <derrickstolee@xxxxxxxxxx>
When computing the generation numbers for a commit-graph, we compute
the corrected commit dates and then check if their offsets from the
actual dates is too large to fit in the 32-bit Generation Data chunk.
However, there is a problem with this approach: if we have parsed the
generation data from the previous commit-graph, then we continue the
loop because the corrected commit date is already computed. This causes
an under-count in the number of overflow values.
It is incorrect to add an increment to num_generation_data_overflows
next to this 'continue' statement, because we might start
double-counting commits that are computed because of the depth-first
search walk from a commit with an earlier OID.
Instead, iterate over the full commit list at the end, checking the
offsets to see how many grow beyond the maximum value.
Create a new t5328-commit-graph-64-bit-time.sh test script to handle
special cases of testing 64-bit timestampes. This helps demonstrate this
bug in more cases. It still won't hit all potential cases until the next
change, which reenables reading generation numbers. Use the skip_all
trick from 0a2bfccb9c8 (t0051: use "skip_all" under !MINGW in
single-test file, 2022-02-04) to make the output clean when run on a
32-bit system.
Hepled-by: Ævar Arnfjörð Bjarmason <avarab@xxxxxxxxx>
Signed-off-by: Derrick Stolee <derrickstolee@xxxxxxxxxx>
---
commit-graph.c | 10 +++++---
t/t5318-commit-graph.sh | 4 +--
t/t5328-commit-graph-64bit-time.sh | 39 ++++++++++++++++++++++++++++++
3 files changed, 48 insertions(+), 5 deletions(-)
create mode 100755 t/t5328-commit-graph-64bit-time.sh
diff --git a/commit-graph.c b/commit-graph.c
index 265c010122e..a19bd96c2ee 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -1556,12 +1556,16 @@ static void compute_generation_numbers(struct write_commit_graph_context *ctx)
if (current->date && current->date > max_corrected_commit_date)
max_corrected_commit_date = current->date - 1;
commit_graph_data_at(current)->generation = max_corrected_commit_date + 1;
-
- if (commit_graph_data_at(current)->generation - current->date > GENERATION_NUMBER_V2_OFFSET_MAX)
- ctx->num_generation_data_overflows++;
}
}
}
+
+ for (i = 0; i < ctx->commits.nr; i++) {
+ struct commit *c = ctx->commits.list[i];
+ timestamp_t offset = commit_graph_data_at(c)->generation - c->date;
+ if (offset > GENERATION_NUMBER_V2_OFFSET_MAX)
+ ctx->num_generation_data_overflows++;
+ }
stop_progress(&ctx->progress);
}
diff --git a/t/t5318-commit-graph.sh b/t/t5318-commit-graph.sh
index 9e2b5884dae..0ed7e9de8e6 100755
--- a/t/t5318-commit-graph.sh
+++ b/t/t5318-commit-graph.sh
@@ -425,10 +425,10 @@ test_expect_success 'warn on improper hash version' '
)
'
-test_expect_success 'lower layers have overflow chunk' '
+test_expect_success TIME_IS_64BIT,TIME_T_IS_64BIT 'lower layers have overflow chunk' '
cd "$TRASH_DIRECTORY/full" &&
UNIX_EPOCH_ZERO="@0 +0000" &&
- FUTURE_DATE="@2147483646 +0000" &&
+ FUTURE_DATE="@4147483646 +0000" &&
rm -f .git/objects/info/commit-graph &&
test_commit --date "$FUTURE_DATE" future-1 &&
test_commit --date "$UNIX_EPOCH_ZERO" old-1 &&
diff --git a/t/t5328-commit-graph-64bit-time.sh b/t/t5328-commit-graph-64bit-time.sh
new file mode 100755
index 00000000000..28114bcaf47
--- /dev/null
+++ b/t/t5328-commit-graph-64bit-time.sh
@@ -0,0 +1,39 @@
+#!/bin/sh
+
+test_description='commit graph with 64-bit timestamps'
+. ./test-lib.sh
+
+if ! test_have_prereq TIME_IS_64BIT || ! test_have_prereq TIME_T_IS_64BIT
+then
+ skip_all='skipping 64-bit timestamp tests'
+ test_done
+fi
+
+. "$TEST_DIRECTORY"/lib-commit-graph.sh
+
+UNIX_EPOCH_ZERO="@0 +0000"
+FUTURE_DATE="@4147483646 +0000"
+
+GIT_TEST_COMMIT_GRAPH_CHANGED_PATHS=0
+
+test_expect_success 'lower layers have overflow chunk' '
+ rm -f .git/objects/info/commit-graph &&
+ test_commit --date "$FUTURE_DATE" future-1 &&
+ test_commit --date "$UNIX_EPOCH_ZERO" old-1 &&
+ git commit-graph write --reachable &&
+ test_commit --date "$FUTURE_DATE" future-2 &&
+ test_commit --date "$UNIX_EPOCH_ZERO" old-2 &&
+ git commit-graph write --reachable --split=no-merge &&
+ test_commit extra &&
+ git commit-graph write --reachable --split=no-merge &&
+ git commit-graph write --reachable &&
+ graph_read_expect 5 "generation_data generation_data_overflow" &&
+ mv .git/objects/info/commit-graph commit-graph-upgraded &&
+ git commit-graph write --reachable &&
+ graph_read_expect 5 "generation_data generation_data_overflow" &&
+ test_cmp .git/objects/info/commit-graph commit-graph-upgraded
+'
+
+graph_git_behavior 'overflow' '' HEAD~2 HEAD
+
+test_done
--
gitgitgadget
