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https://github.com/git-for-windows/git.git
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fbcc5408fc
compute_reachable_generation_numbers() computes each commit's
generation as
max(c->date, max(parent.generation)) + 1
by walking its parents and accumulating their generations into a
local
uint32_t max_gen = 0;
while info->get_generation() returns timestamp_t and
compute_generation_from_max() already takes its max_gen parameter
as timestamp_t. For v1 (topological levels) the narrowing is
harmless because GENERATION_NUMBER_V1_MAX is less than 2^30, but
for v2 (corrected committer dates) it silently truncates any
parent generation that does not fit in 32 bits, i.e. any parent
whose committer timestamp is at or beyond 2106-02-07 UTC
(>= 2^32).
The truncated max then causes child commits to end up with a
corrected committer date that matches the parent's instead of being
at least 1 higher. The bad value gets written into the commit-graph
and causes problems later, and can be noticed by running `git
commit-graph verify`.
Widen the accumulator to timestamp_t.
This is solely an in-memory arithmetic fix with no on-disk format
change: the on-disk format already encodes timestamp_t values and
existing readers handle them unchanged. This merely allows the code to
compute the correct value to write to disk.
The narrowing was introduced in 80c928d947 (commit-graph:
simplify compute_generation_numbers(), 2023-03-20), which rewired
v2 to use the shared compute_reachable_generation_numbers()
helper; the helper's local accumulator had been declared uint32_t
in the immediately preceding 368d19b0b7 (commit-graph: refactor
compute_topological_levels(), 2023-03-20) when only v1 was using
it, where it was harmless.
Add a new test with a future-dated parent and a present-day child;
without the above fix, `git commit-graph verify` reports the
descendant's stored generation as below parent + 1.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
96 lines
3.1 KiB
Bash
Executable File
96 lines
3.1 KiB
Bash
Executable File
#!/bin/sh
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test_description='commit graph with 64-bit timestamps'
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. ./test-lib.sh
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if ! test_have_prereq TIME_IS_64BIT || ! test_have_prereq TIME_T_IS_64BIT
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then
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skip_all='skipping 64-bit timestamp tests'
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test_done
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fi
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. "$TEST_DIRECTORY"/lib-commit-graph.sh
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. "$TEST_DIRECTORY/lib-chunk.sh"
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UNIX_EPOCH_ZERO="@0 +0000"
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FUTURE_DATE="@4147483646 +0000"
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GIT_TEST_COMMIT_GRAPH_CHANGED_PATHS=0
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test_expect_success 'lower layers have overflow chunk' '
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rm -f .git/objects/info/commit-graph &&
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test_commit --date "$FUTURE_DATE" future-1 &&
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test_commit --date "$UNIX_EPOCH_ZERO" old-1 &&
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git commit-graph write --reachable &&
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test_commit --date "$FUTURE_DATE" future-2 &&
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test_commit --date "$UNIX_EPOCH_ZERO" old-2 &&
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git commit-graph write --reachable --split=no-merge &&
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test_commit extra &&
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git commit-graph write --reachable --split=no-merge &&
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git commit-graph write --reachable &&
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graph_read_expect 5 "generation_data generation_data_overflow" &&
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mv .git/objects/info/commit-graph commit-graph-upgraded &&
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git commit-graph write --reachable &&
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graph_read_expect 5 "generation_data generation_data_overflow" &&
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test_cmp .git/objects/info/commit-graph commit-graph-upgraded
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'
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graph_git_behavior 'overflow' '' HEAD~2 HEAD
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test_expect_success 'set up and verify repo with generation data overflow chunk' '
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git init repo &&
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(
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cd repo &&
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test_commit --date "$UNIX_EPOCH_ZERO" 1 &&
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test_commit 2 &&
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test_commit --date "$UNIX_EPOCH_ZERO" 3 &&
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git commit-graph write --reachable &&
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graph_read_expect 3 generation_data &&
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test_commit --date "$FUTURE_DATE" 4 &&
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test_commit 5 &&
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test_commit --date "$UNIX_EPOCH_ZERO" 6 &&
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git branch left &&
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git reset --hard 3 &&
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test_commit 7 &&
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test_commit --date "$FUTURE_DATE" 8 &&
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test_commit 9 &&
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git branch right &&
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git reset --hard 3 &&
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test_merge M left right &&
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git commit-graph write --reachable &&
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graph_read_expect 10 "generation_data generation_data_overflow" &&
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git commit-graph verify
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)
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'
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graph_git_behavior 'overflow 2' repo left right
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test_expect_success 'single commit with generation data exceeding UINT32_MAX' '
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git init repo-uint32-max &&
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test_commit -C repo-uint32-max --date "@4294967297 +0000" 1 &&
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git -C repo-uint32-max commit-graph write --reachable &&
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graph_read_expect -C repo-uint32-max 1 "generation_data" &&
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git -C repo-uint32-max commit-graph verify
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'
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test_expect_success 'descendant of commit with date exceeding UINT32_MAX' '
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git init repo-uint32-max-descendant &&
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test_commit -C repo-uint32-max-descendant \
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--date "@4294967300 +0000" future-parent &&
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test_commit -C repo-uint32-max-descendant present-day-child &&
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git -C repo-uint32-max-descendant commit-graph write --reachable &&
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git -C repo-uint32-max-descendant commit-graph verify
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'
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test_expect_success PERL_TEST_HELPERS 'reader notices out-of-bounds generation overflow' '
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graph=.git/objects/info/commit-graph &&
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test_when_finished "rm -rf $graph" &&
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git commit-graph write --reachable &&
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corrupt_chunk_file $graph GDO2 clear &&
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test_must_fail git log 2>err &&
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grep "commit-graph overflow generation data is too small" err
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'
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test_done
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