From 96058953c72355efb266abe8e333db4f5715dbd2 Mon Sep 17 00:00:00 2001
From: John McCall <rjmccall@apple.com>
Date: Fri, 12 Feb 2010 06:15:07 +0000
Subject: [PATCH] Fix a bug causing an assertion when a covariant return type
 differed from an overriden type only by reduced qualification.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@95968 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/CGVtable.cpp          | 21 ++++++++++++---------
 test/CodeGenCXX/vtable-layout.cpp | 10 ++++++++++
 2 files changed, 22 insertions(+), 9 deletions(-)

diff --git a/lib/CodeGen/CGVtable.cpp b/lib/CodeGen/CGVtable.cpp
index 1c5384767e..e2ea4736d3 100644
--- a/lib/CodeGen/CGVtable.cpp
+++ b/lib/CodeGen/CGVtable.cpp
@@ -64,8 +64,8 @@ static bool
 TypeConversionRequiresAdjustment(ASTContext &Ctx,
                                  QualType DerivedType, QualType BaseType) {
   // Canonicalize the types.
-  QualType CanDerivedType = Ctx.getCanonicalType(DerivedType);
-  QualType CanBaseType = Ctx.getCanonicalType(BaseType);
+  CanQualType CanDerivedType = Ctx.getCanonicalType(DerivedType);
+  CanQualType CanBaseType = Ctx.getCanonicalType(BaseType);
   
   assert(CanDerivedType->getTypeClass() == CanBaseType->getTypeClass() && 
          "Types must have same type class!");
@@ -75,26 +75,29 @@ TypeConversionRequiresAdjustment(ASTContext &Ctx,
     return false;
   }
   
-  if (const ReferenceType *RT = CanDerivedType->getAs<ReferenceType>()) {
-    CanDerivedType = RT->getPointeeType();
+  if (isa<ReferenceType>(CanDerivedType)) {
+    CanDerivedType = CanDerivedType->getAs<ReferenceType>()->getPointeeType();
     CanBaseType = CanBaseType->getAs<ReferenceType>()->getPointeeType();
-  } else if (const PointerType *PT = CanDerivedType->getAs<PointerType>()) {
-    CanDerivedType = PT->getPointeeType();
+  } else if (isa<PointerType>(CanDerivedType)) {
+    CanDerivedType = CanDerivedType->getAs<PointerType>()->getPointeeType();
     CanBaseType = CanBaseType->getAs<PointerType>()->getPointeeType();
   } else {
     assert(false && "Unexpected return type!");
   }
   
-  if (CanDerivedType == CanBaseType) {
+  // We need to compare unqualified types here; consider
+  //   const T *Base::foo();
+  //   T *Derived::foo();
+  if (CanDerivedType.getUnqualifiedType() == CanBaseType.getUnqualifiedType()) {
     // No adjustment needed.
     return false;
   }
   
   const CXXRecordDecl *DerivedDecl = 
-    cast<CXXRecordDecl>(CanDerivedType->getAs<RecordType>()->getDecl());
+    cast<CXXRecordDecl>(cast<RecordType>(CanDerivedType)->getDecl());
   
   const CXXRecordDecl *BaseDecl = 
-    cast<CXXRecordDecl>(CanBaseType->getAs<RecordType>()->getDecl());
+    cast<CXXRecordDecl>(cast<RecordType>(CanBaseType)->getDecl());
   
   return TypeConversionRequiresAdjustment(Ctx, DerivedDecl, BaseDecl);
 }
diff --git a/test/CodeGenCXX/vtable-layout.cpp b/test/CodeGenCXX/vtable-layout.cpp
index f7db2135d2..6cc1b0b691 100644
--- a/test/CodeGenCXX/vtable-layout.cpp
+++ b/test/CodeGenCXX/vtable-layout.cpp
@@ -113,3 +113,13 @@ struct D : B {
 
 void D::f() { } 
 }
+
+// For now, just verify this doesn't crash.
+namespace test0 {
+  struct Obj {};
+
+  struct Base {           virtual const Obj *foo() = 0; };
+  struct Derived : Base { virtual       Obj *foo() { return new Obj(); } };
+
+  void test(Derived *D) { D->foo(); }
+}
-- 
2.40.0