3 files changed, 105 insertions, 26 deletions

diff --git a/include/clang/Basic/Diagnostic.h b/include/clang/Basic/Diagnostic.h
index d6c8797fc9..13e22a0d5d 100644
--- a/include/clang/Basic/Diagnostic.h
+++ b/include/clang/Basic/Diagnostic.h
@@ -234,6 +234,18 @@ private:
                                   void *Cookie);
   void *ArgToStringCookie;
   ArgToStringFnTy ArgToStringFn;
+
+  /// \brief ID of the "delayed" diagnostic, which is a (typically
+  /// fatal) diagnostic that had to be delayed because it was found
+  /// while emitting another diagnostic.
+  unsigned DelayedDiagID;
+
+  /// \brief First string argument for the delayed diagnostic.
+  std::string DelayedDiagArg1;
+
+  /// \brief Second string argument for the delayed diagnostic.
+  std::string DelayedDiagArg2;
+
 public:
   explicit Diagnostic(DiagnosticClient *client = 0);
   ~Diagnostic();
@@ -400,10 +412,41 @@ public:
   inline DiagnosticBuilder Report(FullSourceLoc Pos, unsigned DiagID);
   inline DiagnosticBuilder Report(unsigned DiagID);
 
+  /// \brief Determine whethere there is already a diagnostic in flight.
+  bool isDiagnosticInFlight() const { return CurDiagID != 0; }
+
+  /// \brief Set the "delayed" diagnostic that will be emitted once
+  /// the current diagnostic completes.
+  ///
+  ///  If a diagnostic is already in-flight but the front end must
+  ///  report a problem (e.g., with an inconsistent file system
+  ///  state), this routine sets a "delayed" diagnostic that will be
+  ///  emitted after the current diagnostic completes. This should
+  ///  only be used for fatal errors detected at inconvenient
+  ///  times. If emitting a delayed diagnostic causes a second delayed
+  ///  diagnostic to be introduced, that second delayed diagnostic
+  ///  will be ignored.
+  ///
+  /// \param DiagID The ID of the diagnostic being delayed.
+  ///
+  /// \param Arg1 A string argument that will be provided to the
+  /// diagnostic. A copy of this string will be stored in the
+  /// Diagnostic object itself.
+  ///
+  /// \param Arg2 A string argument that will be provided to the
+  /// diagnostic. A copy of this string will be stored in the
+  /// Diagnostic object itself.
+  void SetDelayedDiagnostic(unsigned DiagID, llvm::StringRef Arg1 = "",
+                            llvm::StringRef Arg2 = "");
+  
   /// \brief Clear out the current diagnostic.
   void Clear() { CurDiagID = ~0U; }
 
 private:
+  /// \brief Report the delayed diagnostic.
+  void ReportDelayed();
+
+
   /// getDiagnosticMappingInfo - Return the mapping info currently set for the
   /// specified builtin diagnostic.  This returns the high bit encoding, or zero
   /// if the field is completely uninitialized.
@@ -543,29 +586,7 @@ public:
   ///
   /// \returns true if a diagnostic was emitted, false if the
   /// diagnostic was suppressed.
-  bool Emit() {
-    // If DiagObj is null, then its soul was stolen by the copy ctor
-    // or the user called Emit().
-    if (DiagObj == 0) return false;
-
-    // When emitting diagnostics, we set the final argument count into
-    // the Diagnostic object.
-    DiagObj->NumDiagArgs = NumArgs;
-    DiagObj->NumDiagRanges = NumRanges;
-    DiagObj->NumCodeModificationHints = NumCodeModificationHints;
-
-    // Process the diagnostic, sending the accumulated information to the
-    // DiagnosticClient.
-    bool Emitted = DiagObj->ProcessDiag();
-
-    // Clear out the current diagnostic object.
-    DiagObj->Clear();
-
-    // This diagnostic is dead.
-    DiagObj = 0;
-
-    return Emitted;
-  }
+  bool Emit();
 
   /// Destructor - The dtor emits the diagnostic if it hasn't already
   /// been emitted.
diff --git a/lib/Basic/Diagnostic.cpp b/lib/Basic/Diagnostic.cpp
index f7ec873e4c..227c175dc0 100644
--- a/lib/Basic/Diagnostic.cpp
+++ b/lib/Basic/Diagnostic.cpp
@@ -222,6 +222,8 @@ Diagnostic::Diagnostic(DiagnosticClient *client) : Client(client) {
   ArgToStringFn = DummyArgToStringFn;
   ArgToStringCookie = 0;
 
+  DelayedDiagID = 0;
+
   // Set all mappings to 'unset'.
   DiagMappings BlankDiags(diag::DIAG_UPPER_LIMIT/2, 0);
   DiagMappingsStack.push_back(BlankDiags);
@@ -289,6 +291,23 @@ const char *Diagnostic::getDescription(unsigned DiagID) const {
   return CustomDiagInfo->getDescription(DiagID);
 }
 
+void Diagnostic::SetDelayedDiagnostic(unsigned DiagID, llvm::StringRef Arg1,
+                                      llvm::StringRef Arg2) {
+  if (DelayedDiagID)
+    return;
+
+  DelayedDiagID = DiagID;
+  DelayedDiagArg1 = Arg1;
+  DelayedDiagArg1 = Arg2;
+}
+
+void Diagnostic::ReportDelayed() {
+  Report(DelayedDiagID) << DelayedDiagArg1 << DelayedDiagArg2;
+  DelayedDiagID = 0;
+  DelayedDiagArg1.clear();
+  DelayedDiagArg2.clear();
+}
+
 /// getDiagnosticLevel - Based on the way the client configured the Diagnostic
 /// object, classify the specified diagnostic ID into a Level, consumable by
 /// the DiagnosticClient.
@@ -532,6 +551,34 @@ bool Diagnostic::ProcessDiag() {
   return true;
 }
 
+bool DiagnosticBuilder::Emit() {
+  // If DiagObj is null, then its soul was stolen by the copy ctor
+  // or the user called Emit().
+  if (DiagObj == 0) return false;
+
+  // When emitting diagnostics, we set the final argument count into
+  // the Diagnostic object.
+  DiagObj->NumDiagArgs = NumArgs;
+  DiagObj->NumDiagRanges = NumRanges;
+  DiagObj->NumCodeModificationHints = NumCodeModificationHints;
+
+  // Process the diagnostic, sending the accumulated information to the
+  // DiagnosticClient.
+  bool Emitted = DiagObj->ProcessDiag();
+
+  // Clear out the current diagnostic object.
+  DiagObj->Clear();
+
+  // If there was a delayed diagnostic, emit it now.
+  if (DiagObj->DelayedDiagID)
+    DiagObj->ReportDelayed();
+
+  // This diagnostic is dead.
+  DiagObj = 0;
+
+  return Emitted;
+}
+
 
 DiagnosticClient::~DiagnosticClient() {}
 
diff --git a/lib/Basic/SourceManager.cpp b/lib/Basic/SourceManager.cpp
index c34f3e2543..27cb9bebde 100644
--- a/lib/Basic/SourceManager.cpp
+++ b/lib/Basic/SourceManager.cpp
@@ -89,15 +89,26 @@ const llvm::MemoryBuffer *ContentCache::getBuffer(Diagnostic &Diag,
       char *Ptr = const_cast<char*>(Buffer.getPointer()->getBufferStart());
       for (unsigned i = 0, e = Entry->getSize(); i != e; ++i)
         Ptr[i] = FillStr[i % FillStr.size()];
-      Diag.Report(diag::err_cannot_open_file)
-        << Entry->getName() << ErrorStr;
+
+      if (Diag.isDiagnosticInFlight())
+        Diag.SetDelayedDiagnostic(diag::err_cannot_open_file, 
+                                  Entry->getName(), ErrorStr);
+      else 
+        Diag.Report(diag::err_cannot_open_file)
+          << Entry->getName() << ErrorStr;
+
       Buffer.setInt(true);
     } else if (FileInfo.st_size != Entry->getSize() ||
                FileInfo.st_mtime != Entry->getModificationTime()) {
       // Check that the file's size, modification time, and inode are
       // the same as in the file entry (which may have come from a
       // stat cache).
-      Diag.Report(diag::err_file_modified) << Entry->getName();
+      if (Diag.isDiagnosticInFlight())
+        Diag.SetDelayedDiagnostic(diag::err_file_modified, 
+                                  Entry->getName());
+      else 
+        Diag.Report(diag::err_file_modified) << Entry->getName();
+
       Buffer.setInt(true);
     }
   }