Defer loading any pending update records until we've finished deserializing.

This fixes a bug where an update record causes us to load an entity that refers
to an entity we've not finished loading yet, resulting in badness.

llvm-svn: 207603

clang/lib/Serialization/ASTReader.cpp

@@ -3430,6 +3430,9 @@ ASTReader::ASTReadResult ASTReader::ReadAST(const std::string &FileName,
   llvm::SaveAndRestore<SourceLocation>
     SetCurImportLocRAII(CurrentImportLoc, ImportLoc);
 
+  // Defer any pending actions until we get to the end of reading the AST file.
+  Deserializing AnASTFile(this);
+
   // Bump the generation number.
   unsigned PreviousGeneration = CurrentGeneration++;
 
@@ -3742,24 +3745,6 @@ void ASTReader::InitializeContext() {
     DeserializationListener->DeclRead(PREDEF_DECL_TRANSLATION_UNIT_ID, 
                                       Context.getTranslationUnitDecl());
 
-  // For any declarations we have already loaded, load any update records.
-  {
-    // We're not back to a consistent state until all our pending update
-    // records have been loaded. There can be interdependencies between them.
-    Deserializing SomeUpdateRecords(this);
-    ReadingKindTracker ReadingKind(Read_Decl, *this);
-
-    // Make sure we load the declaration update records for the translation
-    // unit, if there are any.
-    // FIXME: Is this necessary any more?
-    loadDeclUpdateRecords(PREDEF_DECL_TRANSLATION_UNIT_ID,
-                          Context.getTranslationUnitDecl());
-
-    for (auto &Update : PendingUpdateRecords)
-      loadDeclUpdateRecords(Update.first, Update.second);
-    PendingUpdateRecords.clear();
-  }
-
   // FIXME: Find a better way to deal with collisions between these
   // built-in types. Right now, we just ignore the problem.
   
@@ -8057,6 +8042,13 @@ void ASTReader::finishPendingActions() {
       Info.D->setDeclContextsImpl(SemaDC, LexicalDC, getContext());
     }
 
+    // Perform any pending declaration updates.
+    while (!PendingUpdateRecords.empty()) {
+      auto Update = PendingUpdateRecords.pop_back_val();
+      ReadingKindTracker ReadingKind(Read_Decl, *this);
+      loadDeclUpdateRecords(Update.first, Update.second);
+    }
+
     // Trigger the import of the full definition of each class that had any
     // odr-merging problems, so we can produce better diagnostics for them.
     for (auto &Merge : PendingOdrMergeFailures) {

clang/lib/Serialization/ASTReaderDecl.cpp

@@ -2801,7 +2801,7 @@ Decl *ASTReader::ReadDeclRecord(DeclID ID) {
   assert(Idx == Record.size());
 
   // Load any relevant update records.
-  loadDeclUpdateRecords(ID, D);
+  PendingUpdateRecords.push_back(std::make_pair(ID, D));
 
   // Load the categories after recursive loading is finished.
   if (ObjCInterfaceDecl *Class = dyn_cast<ObjCInterfaceDecl>(D))

clang/test/Modules/Inputs/templates-left.h

@@ -51,3 +51,8 @@ void useExplicitInstantiation() {
   ExplicitInstantiation<true, false>().f();
   ExplicitInstantiation<true, true>().f();
 }
+
+template<typename> struct DelayUpdates;
+template<> struct DelayUpdates<int>;
+template<typename T> struct DelayUpdates<T*>;
+template<typename T> void testDelayUpdates(DelayUpdates<T> *p = 0) {}

clang/test/Modules/Inputs/templates-top.h

@@ -29,3 +29,5 @@ template<typename T> struct Outer {
 template<bool, bool> struct ExplicitInstantiation {
   void f() {}
 };
+
+template<typename> struct DelayUpdates {};

clang/test/Modules/templates.mm

@@ -84,3 +84,5 @@ template<typename T> void MergePatternDecl<T>::f(Type type) {}
 // CHECK: define {{.*}}@_ZN21ExplicitInstantiationILb0ELb1EE1fEv(
 template struct ExplicitInstantiation<false, true>;
 template struct ExplicitInstantiation<true, true>;
+
+void testDelayUpdatesImpl() { testDelayUpdates<int>(); }