Introduce a flag in SourceManager to treat non-system source files

as "volatile", meaning there's a high enough chance that they may
change while we are trying to use them.

This flag is only enabled by libclang.
Currently "volatile" source files will be stat'ed immediately
before opening them, because the file size stat info
may not be accurate since when we got it (e.g. from the PCH).
This avoids crashes when trying to reference mmap'ed memory
from a file whose size is not what we expect.

Note that there's still a window for a racing issue to occur
but the window for it should be way smaller than before.
We can consider later on to avoid mmap completely on such files.

rdar://11612916

llvm-svn: 160074

1 files changed, 20 insertions, 8 deletions

diff --git a/clang/lib/Frontend/ASTUnit.cpp b/clang/lib/Frontend/ASTUnit.cpp
index 7be25e96b4c..ea2f773c565 100644
--- a/clang/lib/Frontend/ASTUnit.cpp
+++ b/clang/lib/Frontend/ASTUnit.cpp
@@ -215,7 +215,7 @@ ASTUnit::ASTUnit(bool _MainFileIsAST)
     PreambleRebuildCounter(0), SavedMainFileBuffer(0), PreambleBuffer(0),
     NumWarningsInPreamble(0),
     ShouldCacheCodeCompletionResults(false),
-    IncludeBriefCommentsInCodeCompletion(false),
+    IncludeBriefCommentsInCodeCompletion(false), UserFilesAreVolatile(false),
     CompletionCacheTopLevelHashValue(0),
     PreambleTopLevelHashValue(0),
     CurrentTopLevelHashValue(0),
@@ -658,7 +658,8 @@ ASTUnit *ASTUnit::LoadFromASTFile(const std::string &Filename,
                                   RemappedFile *RemappedFiles,
                                   unsigned NumRemappedFiles,
                                   bool CaptureDiagnostics,
-                                  bool AllowPCHWithCompilerErrors) {
+                                  bool AllowPCHWithCompilerErrors,
+                                  bool UserFilesAreVolatile) {
   OwningPtr<ASTUnit> AST(new ASTUnit(true));
 
   // Recover resources if we crash before exiting this method.
@@ -674,8 +675,10 @@ ASTUnit *ASTUnit::LoadFromASTFile(const std::string &Filename,
   AST->CaptureDiagnostics = CaptureDiagnostics;
   AST->Diagnostics = Diags;
   AST->FileMgr = new FileManager(FileSystemOpts);
+  AST->UserFilesAreVolatile = UserFilesAreVolatile;
   AST->SourceMgr = new SourceManager(AST->getDiagnostics(),
-                                     AST->getFileManager());
+                                     AST->getFileManager(),
+                                     UserFilesAreVolatile);
   AST->HeaderInfo.reset(new HeaderSearch(AST->getFileManager(),
                                          AST->getDiagnostics(),
                                          AST->ASTFileLangOpts,
@@ -1077,7 +1080,8 @@ bool ASTUnit::Parse(llvm::MemoryBuffer *OverrideMainBuffer) {
   LangOpts = &Clang->getLangOpts();
   FileSystemOpts = Clang->getFileSystemOpts();
   FileMgr = new FileManager(FileSystemOpts);
-  SourceMgr = new SourceManager(getDiagnostics(), *FileMgr);
+  SourceMgr = new SourceManager(getDiagnostics(), *FileMgr,
+                                UserFilesAreVolatile);
   TheSema.reset();
   Ctx = 0;
   PP = 0;
@@ -1665,7 +1669,8 @@ StringRef ASTUnit::getMainFileName() const {
 
 ASTUnit *ASTUnit::create(CompilerInvocation *CI,
                          IntrusiveRefCntPtr<DiagnosticsEngine> Diags,
-                         bool CaptureDiagnostics) {
+                         bool CaptureDiagnostics,
+                         bool UserFilesAreVolatile) {
   OwningPtr<ASTUnit> AST;
   AST.reset(new ASTUnit(false));
   ConfigureDiags(Diags, 0, 0, *AST, CaptureDiagnostics);
@@ -1673,7 +1678,9 @@ ASTUnit *ASTUnit::create(CompilerInvocation *CI,
   AST->Invocation = CI;
   AST->FileSystemOpts = CI->getFileSystemOpts();
   AST->FileMgr = new FileManager(AST->FileSystemOpts);
-  AST->SourceMgr = new SourceManager(AST->getDiagnostics(), *AST->FileMgr);
+  AST->UserFilesAreVolatile = UserFilesAreVolatile;
+  AST->SourceMgr = new SourceManager(AST->getDiagnostics(), *AST->FileMgr,
+                                     UserFilesAreVolatile);
 
   return AST.take();
 }
@@ -1689,6 +1696,7 @@ ASTUnit *ASTUnit::LoadFromCompilerInvocationAction(CompilerInvocation *CI,
                                              bool PrecompilePreamble,
                                              bool CacheCodeCompletionResults,
                                     bool IncludeBriefCommentsInCodeCompletion,
+                                             bool UserFilesAreVolatile,
                                              OwningPtr<ASTUnit> *ErrAST) {
   assert(CI && "A CompilerInvocation is required");
 
@@ -1696,7 +1704,7 @@ ASTUnit *ASTUnit::LoadFromCompilerInvocationAction(CompilerInvocation *CI,
   ASTUnit *AST = Unit;
   if (!AST) {
     // Create the AST unit.
-    OwnAST.reset(create(CI, Diags, CaptureDiagnostics));
+    OwnAST.reset(create(CI, Diags, CaptureDiagnostics, UserFilesAreVolatile));
     AST = OwnAST.get();
   }
   
@@ -1859,7 +1867,8 @@ ASTUnit *ASTUnit::LoadFromCompilerInvocation(CompilerInvocation *CI,
                                              bool PrecompilePreamble,
                                              TranslationUnitKind TUKind,
                                              bool CacheCodeCompletionResults,
-                                    bool IncludeBriefCommentsInCodeCompletion) {
+                                    bool IncludeBriefCommentsInCodeCompletion,
+                                             bool UserFilesAreVolatile) {
   // Create the AST unit.
   OwningPtr<ASTUnit> AST;
   AST.reset(new ASTUnit(false));
@@ -1872,6 +1881,7 @@ ASTUnit *ASTUnit::LoadFromCompilerInvocation(CompilerInvocation *CI,
   AST->IncludeBriefCommentsInCodeCompletion
     = IncludeBriefCommentsInCodeCompletion;
   AST->Invocation = CI;
+  AST->UserFilesAreVolatile = UserFilesAreVolatile;
   
   // Recover resources if we crash before exiting this method.
   llvm::CrashRecoveryContextCleanupRegistrar<ASTUnit>
@@ -1898,6 +1908,7 @@ ASTUnit *ASTUnit::LoadFromCommandLine(const char **ArgBegin,
                                       bool IncludeBriefCommentsInCodeCompletion,
                                       bool AllowPCHWithCompilerErrors,
                                       bool SkipFunctionBodies,
+                                      bool UserFilesAreVolatile,
                                       OwningPtr<ASTUnit> *ErrAST) {
   if (!Diags.getPtr()) {
     // No diagnostics engine was provided, so create our own diagnostics object
@@ -1957,6 +1968,7 @@ ASTUnit *ASTUnit::LoadFromCommandLine(const char **ArgBegin,
   AST->ShouldCacheCodeCompletionResults = CacheCodeCompletionResults;
   AST->IncludeBriefCommentsInCodeCompletion
     = IncludeBriefCommentsInCodeCompletion;
+  AST->UserFilesAreVolatile = UserFilesAreVolatile;
   AST->NumStoredDiagnosticsFromDriver = StoredDiagnostics.size();
   AST->StoredDiagnostics.swap(StoredDiagnostics);
   AST->Invocation = CI;