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d3af1c193d
In 80c928d947 (commit-graph: simplify compute_generation_numbers(),
2023-03-20), the code to compute generation numbers was simplified to
use the same infrastructure as is used to compute topological levels.
This refactoring introduced a bug where the generation numbers are
truncated when they exceed UINT32_MAX because we explicitly cast the
computed generation number to `uint32_t`. This is not required though:
both the computed value and the field of `struct commit_graph_data` are
of the same type `timestamp_t` already, so casting to `uint32_t` will
cause truncation.
This cast can cause us to miscompute generation data overflows:
1. Given a commit with no parents and committer date
`UINT32_MAX + 1`.
2. We compute its generation number as `UINT32_MAX + 1`, but
truncate it to `1`.
3. We calculate the generation offset via `$generation - $date`,
which is thus `1 - (UINT32_MAX + 1)`. The computation underflows
and we thus end up with an offset that is bigger than the maximum
allowed offset.
As a result, we'd be writing generation data overflow information into
the commit-graph that is bogus and ultimately not even required.
Fix this bug by removing the needless cast.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
75 lines
2.2 KiB
Bash
Executable file
75 lines
2.2 KiB
Bash
Executable file
#!/bin/sh
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test_description='commit graph with 64-bit timestamps'
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. ./test-lib.sh
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if ! test_have_prereq TIME_IS_64BIT || ! test_have_prereq TIME_T_IS_64BIT
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then
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skip_all='skipping 64-bit timestamp tests'
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test_done
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fi
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. "$TEST_DIRECTORY"/lib-commit-graph.sh
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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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mkdir repo &&
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cd repo &&
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git init &&
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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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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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cd repo-uint32-max &&
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test_commit --date "@4294967297 +0000" 1 &&
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git commit-graph write --reachable &&
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graph_read_expect 1 "generation_data" &&
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git commit-graph verify
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'
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test_done
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