1 files changed, 11 insertions, 0 deletions
diff --git a/lib/Frontend/PrintPreprocessedOutput.cpp b/lib/Frontend/PrintPreprocessedOutput.cpp
index 30707dc0c0..0dc9281166 100644
--- a/lib/Frontend/PrintPreprocessedOutput.cpp
+++ b/lib/Frontend/PrintPreprocessedOutput.cpp
@@ -95,6 +95,7 @@ private:
   bool DisableLineMarkers;
   bool DumpDefines;
   bool UseLineDirective;
+  bool IsFirstFileEntered;
 public:
   PrintPPOutputPPCallbacks(Preprocessor &pp, raw_ostream &os,
                            bool lineMarkers, bool defines)
@@ -107,6 +108,7 @@ public:
     EmittedDirectiveOnThisLine = false;
     FileType = SrcMgr::C_User;
     Initialized = false;
+    IsFirstFileEntered = false;
 
     // If we're in microsoft mode, use normal #line instead of line markers.
     UseLineDirective = PP.getLangOpts().MicrosoftExt;
@@ -273,6 +275,15 @@ void PrintPPOutputPPCallbacks::FileChanged(SourceLocation Loc,
     Initialized = true;
   }
 
+  // Do not emit an enter marker for the main file (which we expect is the first
+  // entered file). This matches gcc, and improves compatibility with some tools
+  // which track the # line markers as a way to determine when the preprocessed
+  // output is in the context of the main file.
+  if (Reason == PPCallbacks::EnterFile && !IsFirstFileEntered) {
+    IsFirstFileEntered = true;
+    return;
+  }
+
   switch (Reason) {
   case PPCallbacks::EnterFile:
     WriteLineInfo(CurLine, " 1", 2);