Don't cache dep file #2322
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Don't cache dep file #2322
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sccache has two modes: - normal mode - preprocessor cache mode (aka direct mode in ccache) In the former case, the preprocessor is invoked and creates the dep file itself. Whatever sccache does after that is going to overwrite a fresh file with potentially wrong information, since the cache key is not indexed on the elements that would affect the contents of the dep file, resulting in issue mozilla#2321. In the latter case, sccache currently doesn't handle the situation appropriately (issue mozilla#2194), which is why preprocessor cache mode is automatically disabled when the dependency flags are on the command line (mozilla#2195). Which also means we fallback to the case above.
Codecov ReportAll modified and coverable lines are covered by tests ✅
Additional details and impacted files@@ Coverage Diff @@
## main #2322 +/- ##
==========================================
- Coverage 30.91% 0 -30.92%
==========================================
Files 53 0 -53
Lines 20112 0 -20112
Branches 9755 0 -9755
==========================================
- Hits 6217 0 -6217
+ Misses 7922 0 -7922
+ Partials 5973 0 -5973 ☔ View full report in Codecov by Sentry. |
ahartmetz
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May 18, 2025
This reverts the "main" code changes of commit c0a0b6e but keeps the added test. A better fix will work as follows: - Always store the dep file in the cache - In non-preprocessor cache mode, which doesn't consider things like file name and included file names, so it can confuse cache entries with same preprocessed content but different dep files: do not restore the dep file. It is not necessary anyway because local preprocessing will produce the file. - In preprocessor cache mode, which uses input file names and hashes to distinguish cache entries, but does not run the preprocessor: *do* restore the dep file.
ahartmetz
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May 24, 2025
This reverts the "main" code changes of commit c0a0b6e but keeps the added test. A better fix will work as follows: - Always store the dep file in the cache - In non-preprocessor cache mode, which doesn't consider things like file name and included file names, so it can confuse cache entries with same preprocessed content but different dep files: do not restore the dep file. It is not necessary anyway because local preprocessing will produce the file. - In preprocessor cache mode, which uses input file names and hashes to distinguish cache entries, but does not run the preprocessor: *do* restore the dep file. It is both safe and necessary.
ahartmetz
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Jun 1, 2025
This reverts the "main" code changes of commit c0a0b6e but keeps the added test. A fix that is better than disabling preprocessor cache mode whenever the compiler generates a dep file seems possible.
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sccache has two modes:
In the former case, the preprocessor is invoked and creates the dep file itself. Whatever sccache does after that is going to overwrite a fresh file with potentially wrong information, since the cache key is not indexed on the elements that would affect the contents of the dep file, resulting in issue #2321.
In the latter case, sccache currently doesn't handle the situation appropriately (issue #2194), which is why preprocessor cache mode is automatically disabled when the dependency flags are on the command line (#2195). Which also means we fallback to the case above.