fuzz: merge profiles from parallel fuzzer workers - #823
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Give each worker its own raw profile, then merge the profiles after the fuzzer completes. This prevents parallel workers from overwriting coverage data. Signed-off-by: Lynsey Rydberg <lyrydber@microsoft.com>
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #823 +/- ##
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- Coverage 59.48% 58.77% -0.71%
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Files 24 24
Lines 4226 4226
Branches 655 655
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- Hits 2514 2484 -30
Misses 1471 1471
- Partials 241 271 +30 ☔ View full report in Codecov by Harness. 🚀 New features to boost your workflow:
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The fuzzers run up to 24 workers, but all workers currently write to one
.profrawfile. Their exit-time writes can overwrite or race with each other, making direct fuzz-run coverage data unreliable.Write one raw profile per worker using LLVM's
%pexpansion, merge the shards with thellvm-profdatamatching the selected compiler, then remove the raw shards after a successful merge.Validated with a
fuzz-tftpbootrun:llvm-cov reportsuccessfully consumed the merged profile.cov-analysiscontinues to work as well.