diff --git a/clang/include/clang/Basic/Diagnostic.h b/clang/include/clang/Basic/Diagnostic.h
--- a/clang/include/clang/Basic/Diagnostic.h
+++ b/clang/include/clang/Basic/Diagnostic.h
@@ -888,7 +888,10 @@
                             StringRef Arg2 = "", StringRef Arg3 = "");
 
   /// Clear out the current diagnostic.
-  void Clear() { CurDiagID = std::numeric_limits<unsigned>::max(); }
+  void Clear() {
+    CurDiagID = std::numeric_limits<unsigned>::max();
+    CurDelayedDiagID = 0;
+  }
 
   /// Return the value associated with this diagnostic flag.
   StringRef getFlagValue() const { return FlagValue; }
@@ -918,6 +921,11 @@
   /// diagnostic in flight.
   unsigned CurDiagID;
 
+  /// The ID of the current delayed diagnostic being reported.
+  //
+  // This is set to 0 when there is no delayed diagnostic in flight
+  unsigned CurDelayedDiagID;
+
   enum {
     /// The maximum number of arguments we can hold.
     ///
diff --git a/clang/lib/Basic/Diagnostic.cpp b/clang/lib/Basic/Diagnostic.cpp
--- a/clang/lib/Basic/Diagnostic.cpp
+++ b/clang/lib/Basic/Diagnostic.cpp
@@ -132,6 +132,7 @@
   CurDiagID = std::numeric_limits<unsigned>::max();
   LastDiagLevel = DiagnosticIDs::Ignored;
   DelayedDiagID = 0;
+  CurDelayedDiagID = 0;
 
   // Clear state related to #pragma diagnostic.
   DiagStates.clear();
@@ -146,7 +147,7 @@
 
 void DiagnosticsEngine::SetDelayedDiagnostic(unsigned DiagID, StringRef Arg1,
                                              StringRef Arg2, StringRef Arg3) {
-  if (DelayedDiagID)
+  if (CurDelayedDiagID || DelayedDiagID)
     return;
 
   DelayedDiagID = DiagID;
@@ -156,9 +157,11 @@
 }
 
 void DiagnosticsEngine::ReportDelayed() {
-  unsigned ID = DelayedDiagID;
+  CurDelayedDiagID = DelayedDiagID;
   DelayedDiagID = 0;
-  Report(ID) << DelayedDiagArg1 << DelayedDiagArg2 << DelayedDiagArg3;
+  Report(CurDelayedDiagID) << DelayedDiagArg1 << DelayedDiagArg2
+                           << DelayedDiagArg3;
+  CurDelayedDiagID = 0;
 }
 
 void DiagnosticsEngine::DiagStateMap::appendFirst(DiagState *State) {
@@ -521,7 +524,9 @@
   Clear();
 
   // If there was a delayed diagnostic, emit it now.
-  if (!Force && DelayedDiagID)
+  // unless we are currently emitting a delayed diagnostic,
+  // as that leads to the potential of endless reporting.
+  if (!Force && DelayedDiagID && !CurDelayedDiagID)
     ReportDelayed();
 
   return Emitted;