2 files changed, 22 insertions, 8 deletions
diff --git a/lib/Basic/FileManager.cpp b/lib/Basic/FileManager.cpp
index ddf8934b62..b921f3e0d9 100644
--- a/lib/Basic/FileManager.cpp
+++ b/lib/Basic/FileManager.cpp
@@ -488,15 +488,21 @@ void FileManager::FixupRelativePath(SmallVectorImpl<char> &path) const {
 }
 
 llvm::MemoryBuffer *FileManager::
-getBufferForFile(const FileEntry *Entry, std::string *ErrorStr) {
+getBufferForFile(const FileEntry *Entry, std::string *ErrorStr,
+                 bool isVolatile) {
   OwningPtr<llvm::MemoryBuffer> Result;
   llvm::error_code ec;
 
+  uint64_t FileSize = Entry->getSize();
+  // If there's a high enough chance that the file have changed since we
+  // got its size, force a stat before opening it.
+  if (isVolatile)
+    FileSize = -1;
+
   const char *Filename = Entry->getName();
   // If the file is already open, use the open file descriptor.
   if (Entry->FD != -1) {
-    ec = llvm::MemoryBuffer::getOpenFile(Entry->FD, Filename, Result,
-                                         Entry->getSize());
+    ec = llvm::MemoryBuffer::getOpenFile(Entry->FD, Filename, Result, FileSize);
     if (ErrorStr)
       *ErrorStr = ec.message();
 
@@ -508,7 +514,7 @@ getBufferForFile(const FileEntry *Entry, std::string *ErrorStr) {
   // Otherwise, open the file.
 
   if (FileSystemOpts.WorkingDir.empty()) {
-    ec = llvm::MemoryBuffer::getFile(Filename, Result, Entry->getSize());
+    ec = llvm::MemoryBuffer::getFile(Filename, Result, FileSize);
     if (ec && ErrorStr)
       *ErrorStr = ec.message();
     return Result.take();
@@ -516,7 +522,7 @@ getBufferForFile(const FileEntry *Entry, std::string *ErrorStr) {
 
   SmallString<128> FilePath(Entry->getName());
   FixupRelativePath(FilePath);
-  ec = llvm::MemoryBuffer::getFile(FilePath.str(), Result, Entry->getSize());
+  ec = llvm::MemoryBuffer::getFile(FilePath.str(), Result, FileSize);
   if (ec && ErrorStr)
     *ErrorStr = ec.message();
   return Result.take();
diff --git a/lib/Basic/SourceManager.cpp b/lib/Basic/SourceManager.cpp
index 5dc100a07a..9ec2474299 100644
--- a/lib/Basic/SourceManager.cpp
+++ b/lib/Basic/SourceManager.cpp
@@ -97,7 +97,10 @@ const llvm::MemoryBuffer *ContentCache::getBuffer(DiagnosticsEngine &Diag,
   }    
 
   std::string ErrorStr;
-  Buffer.setPointer(SM.getFileManager().getBufferForFile(ContentsEntry, &ErrorStr));
+  bool isVolatile = SM.userFilesAreVolatile() && !IsSystemFile;
+  Buffer.setPointer(SM.getFileManager().getBufferForFile(ContentsEntry,
+                                                         &ErrorStr,
+                                                         isVolatile));
 
   // If we were unable to open the file, then we are in an inconsistent
   // situation where the content cache referenced a file which no longer
@@ -367,8 +370,10 @@ LineTableInfo &SourceManager::getLineTable() {
 // Private 'Create' methods.
 //===----------------------------------------------------------------------===//
 
-SourceManager::SourceManager(DiagnosticsEngine &Diag, FileManager &FileMgr)
+SourceManager::SourceManager(DiagnosticsEngine &Diag, FileManager &FileMgr,
+                             bool UserFilesAreVolatile)
   : Diag(Diag), FileMgr(FileMgr), OverridenFilesKeepOriginalName(true),
+    UserFilesAreVolatile(UserFilesAreVolatile),
     ExternalSLocEntries(0), LineTable(0), NumLinearScans(0),
     NumBinaryProbes(0), FakeBufferForRecovery(0),
     FakeContentCacheForRecovery(0) {
@@ -426,7 +431,8 @@ void SourceManager::clearIDTables() {
 /// getOrCreateContentCache - Create or return a cached ContentCache for the
 /// specified file.
 const ContentCache *
-SourceManager::getOrCreateContentCache(const FileEntry *FileEnt) {
+SourceManager::getOrCreateContentCache(const FileEntry *FileEnt,
+                                       bool isSystemFile) {
   assert(FileEnt && "Didn't specify a file entry to use?");
 
   // Do we already have information about this file?
@@ -455,6 +461,8 @@ SourceManager::getOrCreateContentCache(const FileEntry *FileEnt) {
     new (Entry) ContentCache(FileEnt);
   }
 
+  Entry->IsSystemFile = isSystemFile;
+
   return Entry;
 }