2 files changed, 18 insertions, 3 deletions
diff --git a/clang/lib/AST/RecordLayoutBuilder.cpp b/clang/lib/AST/RecordLayoutBuilder.cpp
index 34d4a7e5865..143fc61da2b 100644
--- a/clang/lib/AST/RecordLayoutBuilder.cpp
+++ b/clang/lib/AST/RecordLayoutBuilder.cpp
@@ -216,10 +216,12 @@ void EmptySubobjectMap::AddSubobjectAtOffset(const CXXRecordDecl *RD,
   if (!RD->isEmpty())
     return;
 
+  // If we have empty structures inside an union, we can assign both
+  // the same offset. Just avoid pushing them twice in the list.
   ClassVectorTy& Classes = EmptyClassOffsets[Offset];
-  assert(std::find(Classes.begin(), Classes.end(), RD) == Classes.end() &&
-         "Duplicate empty class detected!");
-
+  if (std::find(Classes.begin(), Classes.end(), RD) != Classes.end())
+    return;
+  
   Classes.push_back(RD);
   
   // Update the empty class offset.
diff --git a/clang/test/CodeGenCXX/empty-classes.cpp b/clang/test/CodeGenCXX/empty-classes.cpp
index 59124e3d55b..1ce1dad40ff 100644
--- a/clang/test/CodeGenCXX/empty-classes.cpp
+++ b/clang/test/CodeGenCXX/empty-classes.cpp
@@ -53,6 +53,19 @@ int f() {
   return 0;
 }
 
+namespace PR8796 {
+  struct FreeCell {
+  };
+  union ThingOrCell {
+    FreeCell t;
+    FreeCell cell;
+  };
+  struct Things {
+    ThingOrCell things;
+  };
+  Things x;
+}
+
 #ifdef HARNESS
 extern "C" void printf(const char *, ...);