When deserializing CXXBaseSpecifiers (and offsets), make sure to walk the chain in the correct order.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@127315 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Serialization/ASTReader.cpp

@@ -3730,11 +3730,13 @@ ASTReader::GetCXXBaseSpecifiersOffset(serialization::CXXBaseSpecifiersID ID) {
   --ID;
   uint64_t Offset = 0;
   for (unsigned I = 0, N = Chain.size(); I != N; ++I) {
-    if (ID < Chain[I]->LocalNumCXXBaseSpecifiers)
-      return Offset + Chain[I]->CXXBaseSpecifiersOffsets[ID];
+    PerFileData &F = *Chain[N - I - 1];
+
+    if (ID < F.LocalNumCXXBaseSpecifiers)
+      return Offset + F.CXXBaseSpecifiersOffsets[ID];
     
-    ID -= Chain[I]->LocalNumCXXBaseSpecifiers;
-    Offset += Chain[I]->SizeInBits;
+    ID -= F.LocalNumCXXBaseSpecifiers;
+    Offset += F.SizeInBits;
   }
   
   assert(false && "CXXBaseSpecifiers not found");
@@ -3745,14 +3747,14 @@ CXXBaseSpecifier *ASTReader::GetExternalCXXBaseSpecifiers(uint64_t Offset) {
   // Figure out which AST file contains this offset.
   PerFileData *F = 0;
   for (unsigned I = 0, N = Chain.size(); I != N; ++I) {
-    if (Offset < Chain[I]->SizeInBits) {
-      F = Chain[I];
+    if (Offset < Chain[N - I - 1]->SizeInBits) {
+      F = Chain[N - I - 1];
       break;
     }
     
-    Offset -= Chain[I]->SizeInBits;
+    Offset -= Chain[N - I - 1]->SizeInBits;
   }
-  
+
   if (!F) {
     Error("Malformed AST file: C++ base specifiers at impossible offset");
     return 0;

test/PCH/chain-cxx.cpp

@@ -34,6 +34,9 @@ struct S<T *> { typedef int H; };
 template <typename T> struct TS2;
 typedef TS2<int> TS2int;
 
+template <typename T> struct TestBaseSpecifiers { };
+template<typename T> struct TestBaseSpecifiers2 : TestBaseSpecifiers<T> { };
+
 //===----------------------------------------------------------------------===//
 #elif not defined(HEADER2)
 #define HEADER2
@@ -73,6 +76,9 @@ struct S<int &> { typedef int L; };
 
 template <typename T> struct TS2 { };
 
+struct TestBaseSpecifiers3 { };
+struct TestBaseSpecifiers4 : TestBaseSpecifiers3 { };
+
 struct A { };
 struct B : A { };