Propagate stat failures to shared cache by adding forgotten reference

Author: jansvoboda11

clang/lib/Tooling/DependencyScanning/DependencyScanningFilesystem.cpp

@@ -130,11 +130,12 @@ DependencyScanningFilesystemSharedCache::CacheShard::
     getOrEmplaceEntryForFilename(StringRef Filename,
                                  llvm::ErrorOr<llvm::vfs::Status> Stat) {
   std::lock_guard<std::mutex> LockGuard(CacheLock);
-  const CachedFileSystemEntry *StoredEntry = CacheByFilename[Filename].first;
-  if (!StoredEntry)
-    StoredEntry =
+  auto [It, Inserted] = CacheByFilename.insert({Filename, {nullptr, nullptr}});
+  auto &[CachedEntry, CachedRealPath] = It->getValue();
+  if (!CachedEntry)
+    CachedEntry =
         new (EntryStorage.Allocate()) CachedFileSystemEntry(std::move(Stat));
-  return *StoredEntry;
+  return *CachedEntry;
 }
 
 const CachedFileSystemEntry &

clang/unittests/Tooling/DependencyScanning/DependencyScanningFilesystemTest.cpp

@@ -16,11 +16,17 @@ using namespace clang::tooling::dependencies;
 namespace {
 struct InstrumentingFilesystem
     : llvm::RTTIExtends<InstrumentingFilesystem, llvm::vfs::ProxyFileSystem> {
+  unsigned NumStatusCalls = 0;
   unsigned NumGetRealPathCalls = 0;
 
   using llvm::RTTIExtends<InstrumentingFilesystem,
                           llvm::vfs::ProxyFileSystem>::RTTIExtends;
 
+  llvm::ErrorOr<llvm::vfs::Status> status(const llvm::Twine &Path) override {
+    ++NumStatusCalls;
+    return ProxyFileSystem::status(Path);
+  }
+
   std::error_code getRealPath(const llvm::Twine &Path,
                               llvm::SmallVectorImpl<char> &Output) override {
     ++NumGetRealPathCalls;
@@ -29,6 +35,29 @@ struct InstrumentingFilesystem
 };
 } // namespace
 
+TEST(DependencyScanningWorkerFilesystem, CacheStatusFailures) {
+  auto InMemoryFS = llvm::makeIntrusiveRefCnt<llvm::vfs::InMemoryFileSystem>();
+
+  auto InstrumentingFS =
+      llvm::makeIntrusiveRefCnt<InstrumentingFilesystem>(InMemoryFS);
+
+  DependencyScanningFilesystemSharedCache SharedCache;
+  DependencyScanningWorkerFilesystem DepFS(SharedCache, InstrumentingFS);
+  DependencyScanningWorkerFilesystem DepFS2(SharedCache, InstrumentingFS);
+
+  DepFS.status("/foo.c");
+  EXPECT_EQ(InstrumentingFS->NumStatusCalls, 1u);
+
+  DepFS.status("/foo.c");
+  EXPECT_EQ(InstrumentingFS->NumStatusCalls, 1u); // Cached, no increase.
+
+  DepFS.status("/bar.c");
+  EXPECT_EQ(InstrumentingFS->NumStatusCalls, 2u);
+
+  DepFS2.status("/foo.c");
+  EXPECT_EQ(InstrumentingFS->NumStatusCalls, 2u); // Shared cache.
+}
+
 TEST(DependencyScanningFilesystem, CacheGetRealPath) {
   auto InMemoryFS = llvm::makeIntrusiveRefCnt<llvm::vfs::InMemoryFileSystem>();
   InMemoryFS->setCurrentWorkingDirectory("/");