[clang] Don't silently inherit the VFS from FileManager (llvm#164323)

Since llvm#158381 the
`CompilerInstance` is aware of the VFS and co-owns it. To reduce scope
of that PR, the VFS was being inherited from the `FileManager` during
`setFileManager()` if it wasn't configured before. However, the
implementation of that setter was buggy. This PR fixes the bug, and
moves us closer to the long-term goal of `CompilerInstance` requiring
the VFS to be configured explicitly and owned by the instance.

Author: jansvoboda11

clang-tools-extra/clang-include-fixer/IncludeFixer.cpp

@@ -90,6 +90,7 @@ bool IncludeFixerActionFactory::runInvocation(
 
   // Set up Clang.
   CompilerInstance Compiler(std::move(Invocation), std::move(PCHContainerOps));
+  Compiler.setVirtualFileSystem(Files->getVirtualFileSystemPtr());
   Compiler.setFileManager(Files);
 
   // Create the compiler's actual diagnostics engine. We want to drop all

clang/include/clang/Frontend/ASTUnit.h

@@ -488,6 +488,11 @@ class ASTUnit {
     return *PPOpts;
   }
 
+  IntrusiveRefCntPtr<llvm::vfs::FileSystem> getVirtualFileSystemPtr() {
+    // FIXME: Don't defer VFS ownership to the FileManager.
+    return FileMgr->getVirtualFileSystemPtr();
+  }
+
   const FileManager &getFileManager() const { return *FileMgr; }
   FileManager &getFileManager() { return *FileMgr; }
 

clang/include/clang/Frontend/CompilerInstance.h

@@ -504,9 +504,13 @@ class CompilerInstance : public ModuleLoader {
     FileMgr.resetWithoutRelease();
   }
 
-  /// Replace the current file manager and virtual file system.
+  /// Replace the current file manager.
   void setFileManager(FileManager *Value);
 
+  /// @}
+  /// @name Output Manager
+  /// @{
+
   /// Set the output manager.
   void setOutputBackend(IntrusiveRefCntPtr<llvm::vfs::OutputBackend> NewOutputs);
 

clang/lib/Frontend/ASTUnit.cpp

@@ -1640,6 +1640,7 @@ ASTUnit *ASTUnit::LoadFromCompilerInvocationAction(
   AST->Reader = nullptr;
 
   // Create a file manager object to provide access to and cache the filesystem.
+  Clang->setVirtualFileSystem(AST->getVirtualFileSystemPtr());
   Clang->setFileManager(&AST->getFileManager());
 
   // Create the source manager.
@@ -2277,6 +2278,7 @@ void ASTUnit::CodeComplete(
          "IR inputs not support here!");
 
   // Use the source and file managers that we were given.
+  Clang->setVirtualFileSystem(FileMgr.getVirtualFileSystemPtr());
   Clang->setFileManager(&FileMgr);
   Clang->setSourceManager(&SourceMgr);
 

clang/lib/Frontend/CompilerInstance.cpp

@@ -173,8 +173,6 @@ bool CompilerInstance::createTarget() {
 }
 
 void CompilerInstance::setFileManager(FileManager *Value) {
-  if (!hasVirtualFileSystem())
-    setVirtualFileSystem(Value->getVirtualFileSystemPtr());
   assert(Value == nullptr ||
          getVirtualFileSystemPtr() == Value->getVirtualFileSystemPtr());
   FileMgr = Value;

clang/lib/Frontend/FrontendAction.cpp

@@ -985,6 +985,7 @@ bool FrontendAction::BeginSourceFile(CompilerInstance &CI,
 
     // Set the shared objects, these are reset when we finish processing the
     // file, otherwise the CompilerInstance will happily destroy them.
+    CI.setVirtualFileSystem(AST->getVirtualFileSystemPtr());
     CI.setFileManager(&AST->getFileManager());
     CI.setSourceManager(&AST->getSourceManager());
     CI.setPreprocessor(AST->getPreprocessorPtr());

clang/lib/Frontend/PrecompiledPreamble.cpp

@@ -479,14 +479,12 @@ llvm::ErrorOr<PrecompiledPreamble> PrecompiledPreamble::Build(
   Diagnostics.Reset();
   ProcessWarningOptions(Diagnostics, Clang->getDiagnosticOpts(), *VFS);
 
-  Clang->createVirtualFileSystem(VFS, Diagnostics.getClient());
-
   // Create a file manager object to provide access to and cache the filesystem.
+  Clang->createVirtualFileSystem(VFS);
   Clang->createFileManager();
 
   // Create the source manager.
-  Clang->setSourceManager(
-      new SourceManager(Diagnostics, Clang->getFileManager()));
+  Clang->createSourceManager();
 
   auto PreambleDepCollector = std::make_shared<PreambleDependencyCollector>();
   Clang->addDependencyCollector(PreambleDepCollector);

clang/lib/StaticAnalyzer/Frontend/ModelInjector.cpp

@@ -93,6 +93,7 @@ void ModelInjector::onBodySynthesis(const NamedDecl *D) {
 
   // The instance wants to take ownership, however DisableFree frontend option
   // is set to true to avoid double free issues
+  Instance.setVirtualFileSystem(CI.getVirtualFileSystemPtr());
   Instance.setFileManager(&CI.getFileManager());
   Instance.setSourceManager(&SM);
   Instance.setPreprocessor(CI.getPreprocessorPtr());

clang/lib/Tooling/Tooling.cpp

@@ -445,6 +445,7 @@ bool FrontendActionFactory::runInvocation(
     DiagnosticConsumer *DiagConsumer) {
   // Create a compiler instance to handle the actual work.
   CompilerInstance Compiler(std::move(Invocation), std::move(PCHContainerOps));
+  Compiler.setVirtualFileSystem(Files->getVirtualFileSystemPtr());
   Compiler.setFileManager(Files);
 
   // The FrontendAction can have lifetime requirements for Compiler or its

clang/tools/clang-installapi/ClangInstallAPI.cpp

@@ -113,6 +113,7 @@ static bool run(ArrayRef<const char *> Args, const char *ProgName) {
 
   // Set up compilation.
   std::unique_ptr<CompilerInstance> CI(new CompilerInstance());
+  CI->setVirtualFileSystem(FM->getVirtualFileSystemPtr());
   CI->setFileManager(FM.get());
   CI->createDiagnostics();
   if (!CI->hasDiagnostics())