[clang][scan-deps] Add option to disable caching stat failures #11728
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While the source code isn't supposed to change during a build, in some environments it does. This adds an option that disables caching of stat failures, meaning that source files can be added to the build during scanning. This adds a `-no-cache-negative-stats` option to clang-scan-deps to enable this behavior. There are no tests for clang-scan-deps as there's no reliable way to do so from it. A unit test has been added that modifies the filesystem between scans to test it. Internally this uses an environment variable. `CLANG_SCAN_CACHE_NEGATIVE_STATS`: If this is set or set to 1 negative stat caching is enabled. If it's 0 then it's disabled. Negative stat caching is disabled by default.
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@swift-ci please test |
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@swift-ci please test llvm |
jansvoboda11
reviewed
Nov 3, 2025
| static ScanningOptimizations OptimizeArgs; | ||
| static std::string ModuleFilesDir; | ||
| static bool EagerLoadModules; | ||
| static bool CacheNegativeStats = true; |
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The default value here is always overwritten in ParseArgs().
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| EagerLoadModules = Args.hasArg(OPT_eager_load_pcm); | ||
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| CacheNegativeStats = !Args.hasArg(OPT_no_cache_negative_stats); |
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This means clang-scan-deps has a different default to other clients, why is that?
| CASOptions(), nullptr, nullptr, nullptr, ScanningOptimizations::Default, | ||
| /*EagerLoadModules=*/false, | ||
| /*TraceVFS=*/false, llvm::sys::toTimeT(std::chrono::system_clock::now()), | ||
| true); |
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Can you add /*CacheNegativeStats=*/ label here other places the service gets constructed?
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Why is it set to true here? I'd think we'd want to match the default behavior of the libclang API.
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While the source code isn't supposed to change during a build, in some environments it does. This adds an option that disables caching of stat failures, meaning that source files can be added to the build during scanning.
This adds a
-no-cache-negative-statsoption to clang-scan-deps to enable this behavior. There are no tests for clang-scan-deps as there's no reliable way to do so from it. A unit test has been added that modifies the filesystem between scans to test it.Internally this uses an environment variable.
CLANG_SCAN_CACHE_NEGATIVE_STATS: If this is set or set to 1 negative stat caching is enabled. If it's 0 then it's disabled.Negative stat caching is disabled by default.