3 files changed, 9 insertions, 3 deletions
diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index 68faeed6a20..5cd57d70d09 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -8216,8 +8216,11 @@ void ASTReader::finishPendingActions() {
       }
       
       if (auto RD = dyn_cast<CXXRecordDecl>(D)) {
-        for (auto R : RD->redecls())
+        for (auto R : RD->redecls()) {
+          assert((R == D) == R->isThisDeclarationADefinition() &&
+                 "declaration thinks it's the definition but it isn't");
           cast<CXXRecordDecl>(R)->DefinitionData = RD->DefinitionData;
+        }
       }
 
       continue;
diff --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
index 0aa29239915..60cc6bd5971 100644
--- a/clang/lib/Serialization/ASTReaderDecl.cpp
+++ b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -489,7 +489,8 @@ ASTDeclReader::RedeclarableResult ASTDeclReader::VisitTagDecl(TagDecl *TD) {
   
   TD->IdentifierNamespace = Record[Idx++];
   TD->setTagKind((TagDecl::TagKind)Record[Idx++]);
-  TD->setCompleteDefinition(Record[Idx++]);
+  if (!isa<CXXRecordDecl>(TD))
+    TD->setCompleteDefinition(Record[Idx++]);
   TD->setEmbeddedInDeclarator(Record[Idx++]);
   TD->setFreeStanding(Record[Idx++]);
   TD->setCompleteDefinitionRequired(Record[Idx++]);
@@ -3426,6 +3427,7 @@ void ASTDeclReader::UpdateDecl(Decl *D, ModuleFile &ModuleFile,
         Reader.ReadDeclContextStorage(ModuleFile, ModuleFile.DeclsCursor,
                                           std::make_pair(LexicalOffset, 0),
                                           ModuleFile.DeclContextInfos[RD]);
+        Reader.PendingDefinitions.insert(RD);
       }
 
       auto TSK = (TemplateSpecializationKind)Record[Idx++];
diff --git a/clang/lib/Serialization/ASTWriterDecl.cpp b/clang/lib/Serialization/ASTWriterDecl.cpp
index cd8f7ddf599..336c86b6d57 100644
--- a/clang/lib/Serialization/ASTWriterDecl.cpp
+++ b/clang/lib/Serialization/ASTWriterDecl.cpp
@@ -245,7 +245,8 @@ void ASTDeclWriter::VisitTagDecl(TagDecl *D) {
   VisitTypeDecl(D);
   Record.push_back(D->getIdentifierNamespace());
   Record.push_back((unsigned)D->getTagKind()); // FIXME: stable encoding
-  Record.push_back(D->isCompleteDefinition());
+  if (!isa<CXXRecordDecl>(D))
+    Record.push_back(D->isCompleteDefinition());
   Record.push_back(D->isEmbeddedInDeclarator());
   Record.push_back(D->isFreeStanding());
   Record.push_back(D->isCompleteDefinitionRequired());