vendor/llvm-project/llvmorg-12-init-17869-g8e464dd76bef

1 files changed, 41 insertions, 20 deletions

diff --git a/clang/lib/Serialization/ModuleManager.cpp b/clang/lib/Serialization/ModuleManager.cpp
index a42ed2f3c179..40ffa6cfee8f 100644
--- a/clang/lib/Serialization/ModuleManager.cpp
+++ b/clang/lib/Serialization/ModuleManager.cpp
@@ -112,7 +112,7 @@ ModuleManager::addModule(StringRef FileName, ModuleKind Type,
 
   // Look for the file entry. This only fails if the expected size or
   // modification time differ.
-  const FileEntry *Entry;
+  OptionalFileEntryRefDegradesToFileEntryPtr Entry;
   if (Type == MK_ExplicitModule || Type == MK_PrebuiltModule) {
     // If we're not expecting to pull this file out of the module cache, it
     // might have a different mtime due to being moved across filesystems in
@@ -132,15 +132,38 @@ ModuleManager::addModule(StringRef FileName, ModuleKind Type,
     return Missing;
   }
 
+  // The ModuleManager's use of FileEntry nodes as the keys for its map of
+  // loaded modules is less than ideal. Uniqueness for FileEntry nodes is
+  // maintained by FileManager, which in turn uses inode numbers on hosts
+  // that support that. When coupled with the module cache's proclivity for
+  // turning over and deleting stale PCMs, this means entries for different
+  // module files can wind up reusing the same underlying inode. When this
+  // happens, subsequent accesses to the Modules map will disagree on the
+  // ModuleFile associated with a given file. In general, it is not sufficient
+  // to resolve this conundrum with a type like FileEntryRef that stores the
+  // name of the FileEntry node on first access because of path canonicalization
+  // issues. However, the paths constructed for implicit module builds are
+  // fully under Clang's control. We *can*, therefore, rely on their structure
+  // being consistent across operating systems and across subsequent accesses
+  // to the Modules map.
+  auto implicitModuleNamesMatch = [](ModuleKind Kind, const ModuleFile *MF,
+                                     const FileEntry *Entry) -> bool {
+    if (Kind != MK_ImplicitModule)
+      return true;
+    return Entry->getName() == MF->FileName;
+  };
+
   // Check whether we already loaded this module, before
   if (ModuleFile *ModuleEntry = Modules.lookup(Entry)) {
-    // Check the stored signature.
-    if (checkSignature(ModuleEntry->Signature, ExpectedSignature, ErrorStr))
-      return OutOfDate;
-
-    Module = ModuleEntry;
-    updateModuleImports(*ModuleEntry, ImportedBy, ImportLoc);
-    return AlreadyLoaded;
+    if (implicitModuleNamesMatch(Type, ModuleEntry, Entry)) {
+      // Check the stored signature.
+      if (checkSignature(ModuleEntry->Signature, ExpectedSignature, ErrorStr))
+        return OutOfDate;
+
+      Module = ModuleEntry;
+      updateModuleImports(*ModuleEntry, ImportedBy, ImportLoc);
+      return AlreadyLoaded;
+    }
   }
 
   // Allocate a new module.
@@ -265,7 +288,7 @@ void ModuleManager::removeModules(ModuleIterator First, ModuleMap *modMap) {
     if (modMap) {
       StringRef ModuleName = victim->ModuleName;
       if (Module *mod = modMap->findModule(ModuleName)) {
-        mod->setASTFile(nullptr);
+        mod->setASTFile(None);
       }
     }
   }
@@ -435,23 +458,21 @@ void ModuleManager::visit(llvm::function_ref<bool(ModuleFile &M)> Visitor,
   returnVisitState(State);
 }
 
-bool ModuleManager::lookupModuleFile(StringRef FileName,
-                                     off_t ExpectedSize,
+bool ModuleManager::lookupModuleFile(StringRef FileName, off_t ExpectedSize,
                                      time_t ExpectedModTime,
-                                     const FileEntry *&File) {
-  if (FileName == "-") {
-    File = nullptr;
+                                     Optional<FileEntryRef> &File) {
+  File = None;
+  if (FileName == "-")
     return false;
-  }
 
   // Open the file immediately to ensure there is no race between stat'ing and
   // opening the file.
-  auto FileOrErr = FileMgr.getFile(FileName, /*OpenFile=*/true,
-                                   /*CacheFailure=*/false);
-  if (!FileOrErr) {
-    File = nullptr;
+  Optional<FileEntryRef> FileOrErr =
+      expectedToOptional(FileMgr.getFileRef(FileName, /*OpenFile=*/true,
+                                            /*CacheFailure=*/false));
+  if (!FileOrErr)
     return false;
-  }
+
   File = *FileOrErr;
 
   if ((ExpectedSize && ExpectedSize != File->getSize()) ||