8 files changed, 26 insertions, 15 deletions
diff --git a/include/clang/Lex/Preprocessor.h b/include/clang/Lex/Preprocessor.h
index 3ef1fcdbda..a4910f714f 100644
--- a/include/clang/Lex/Preprocessor.h
+++ b/include/clang/Lex/Preprocessor.h
@@ -350,7 +350,7 @@ public:
 
   /// EnterMainSourceFile - Enter the specified FileID as the main source file,
   /// which implicitly adds the builtin defines etc.
-  void EnterMainSourceFile();
+  bool EnterMainSourceFile();
 
   /// EnterSourceFile - Add a source file to the top of the include stack and
   /// start lexing tokens from it instead of the current buffer.  Return true
diff --git a/lib/Frontend/CacheTokens.cpp b/lib/Frontend/CacheTokens.cpp
index 02d6cec8fc..199be3d543 100644
--- a/lib/Frontend/CacheTokens.cpp
+++ b/lib/Frontend/CacheTokens.cpp
@@ -549,7 +549,8 @@ void clang::CacheTokens(Preprocessor &PP, llvm::raw_fd_ostream* OS) {
   // Lex through the entire file.  This will populate SourceManager with
   // all of the header information.
   Token Tok;
-  PP.EnterMainSourceFile();
+  if (PP.EnterMainSourceFile())
+    return;
   do { PP.Lex(Tok); } while (Tok.isNot(tok::eof));
 
   // Generate the PTH file.
diff --git a/lib/Frontend/FrontendActions.cpp b/lib/Frontend/FrontendActions.cpp
index 1e210b42e6..1077f9eb34 100644
--- a/lib/Frontend/FrontendActions.cpp
+++ b/lib/Frontend/FrontendActions.cpp
@@ -185,7 +185,8 @@ void DumpTokensAction::ExecuteAction() {
   Preprocessor &PP = getCompilerInstance().getPreprocessor();
   // Start preprocessing the specified input file.
   Token Tok;
-  PP.EnterMainSourceFile();
+  if (PP.EnterMainSourceFile())
+    return;
   do {
     PP.Lex(Tok);
     PP.DumpToken(Tok, true);
@@ -213,7 +214,8 @@ void ParseOnlyAction::ExecuteAction() {
   llvm::OwningPtr<Action> PA(new MinimalAction(PP));
 
   Parser P(PP, *PA);
-  PP.EnterMainSourceFile();
+  if (PP.EnterMainSourceFile())
+    return;
   P.ParseTranslationUnit();
 }
 
@@ -222,7 +224,8 @@ void PreprocessOnlyAction::ExecuteAction() {
 
   Token Tok;
   // Start parsing the specified input file.
-  PP.EnterMainSourceFile();
+  if (PP.EnterMainSourceFile())
+    return;
   do {
     PP.Lex(Tok);
   } while (Tok.isNot(tok::eof));
@@ -237,7 +240,8 @@ void PrintParseAction::ExecuteAction() {
   llvm::OwningPtr<Action> PA(CreatePrintParserActionsAction(PP, OS));
 
   Parser P(PP, *PA);
-  PP.EnterMainSourceFile();
+  if (PP.EnterMainSourceFile())
+    return;
   P.ParseTranslationUnit();
 }
 
diff --git a/lib/Frontend/PrintPreprocessedOutput.cpp b/lib/Frontend/PrintPreprocessedOutput.cpp
index 44e0e13906..02afd24c24 100644
--- a/lib/Frontend/PrintPreprocessedOutput.cpp
+++ b/lib/Frontend/PrintPreprocessedOutput.cpp
@@ -448,7 +448,8 @@ static int MacroIDCompare(const void* a, const void* b) {
 static void DoPrintMacros(Preprocessor &PP, llvm::raw_ostream *OS) {
   // -dM mode just scans and ignores all tokens in the files, then dumps out
   // the macro table at the end.
-  PP.EnterMainSourceFile();
+  if (PP.EnterMainSourceFile())
+    return;
 
   Token Tok;
   do PP.Lex(Tok);
@@ -495,7 +496,8 @@ void clang::DoPrintPreprocessedInput(Preprocessor &PP, llvm::raw_ostream *OS,
   PP.addPPCallbacks(Callbacks);
 
   // After we have configured the preprocessor, enter the main file.
-  PP.EnterMainSourceFile();
+  if (PP.EnterMainSourceFile())
+    return;
 
   // Consume all of the tokens that come from the predefines buffer.  Those
   // should not be emitted into the output and are guaranteed to be at the
diff --git a/lib/Frontend/RewriteMacros.cpp b/lib/Frontend/RewriteMacros.cpp
index 954e8e23ca..4ffb2978db 100644
--- a/lib/Frontend/RewriteMacros.cpp
+++ b/lib/Frontend/RewriteMacros.cpp
@@ -101,7 +101,8 @@ void clang::RewriteMacrosInInput(Preprocessor &PP, llvm::raw_ostream *OS) {
 
 
   // Get the first preprocessing token.
-  PP.EnterMainSourceFile();
+  if (PP.EnterMainSourceFile())
+    return;
   Token PPTok;
   PP.Lex(PPTok);
 
diff --git a/lib/Lex/Preprocessor.cpp b/lib/Lex/Preprocessor.cpp
index a86799aafa..917a2e7412 100644
--- a/lib/Lex/Preprocessor.cpp
+++ b/lib/Lex/Preprocessor.cpp
@@ -488,7 +488,7 @@ SourceLocation Preprocessor::getLocForEndOfToken(SourceLocation Loc,
 
 /// EnterMainSourceFile - Enter the specified FileID as the main source file,
 /// which implicitly adds the builtin defines etc.
-void Preprocessor::EnterMainSourceFile() {
+bool Preprocessor::EnterMainSourceFile() {
   // We do not allow the preprocessor to reenter the main file.  Doing so will
   // cause FileID's to accumulate information from both runs (e.g. #line
   // information) and predefined macros aren't guaranteed to be set properly.
@@ -497,8 +497,8 @@ void Preprocessor::EnterMainSourceFile() {
 
   // Enter the main file source buffer.
   std::string ErrorStr;
-  bool Res = EnterSourceFile(MainFileID, 0, ErrorStr);
-  assert(!Res && "Entering main file should not fail!");
+  if (EnterSourceFile(MainFileID, 0, ErrorStr))
+    return true;
 
   // Tell the header info that the main file was entered.  If the file is later
   // #imported, it won't be re-entered.
@@ -515,8 +515,7 @@ void Preprocessor::EnterMainSourceFile() {
   assert(!FID.isInvalid() && "Could not create FileID for predefines?");
 
   // Start parsing the predefines.
-  Res = EnterSourceFile(FID, 0, ErrorStr);
-  assert(!Res && "Entering predefines should not fail!");
+  return EnterSourceFile(FID, 0, ErrorStr);
 }
 
 
diff --git a/lib/Sema/ParseAST.cpp b/lib/Sema/ParseAST.cpp
index 898b3c230e..7cd39895f6 100644
--- a/lib/Sema/ParseAST.cpp
+++ b/lib/Sema/ParseAST.cpp
@@ -44,7 +44,8 @@ void clang::ParseAST(Preprocessor &PP, ASTConsumer *Consumer,
 
   Sema S(PP, Ctx, *Consumer, CompleteTranslationUnit, CompletionConsumer);
   Parser P(PP, S);
-  PP.EnterMainSourceFile();
+  if (PP.EnterMainSourceFile())
+    return;
 
   // Initialize the parser.
   P.Initialize();
diff --git a/test/Misc/changed-files.c b/test/Misc/changed-files.c
new file mode 100644
index 0000000000..deeb02a38a
--- /dev/null
+++ b/test/Misc/changed-files.c
@@ -0,0 +1,3 @@
+// RUN: touch %t.c
+// RUN: not %clang -E %t.c -o %t.c 2> %t.stderr
+// RUN: grep "modified" %t.stderr