[PATCH] CodeGen: Properly null-check typeid expressions

[David Majnemer]

Hi rsmith,

Thoroughly check for a pointer dereference which yields a glvalue.  Look
through casts, comma operators, conditional operators, paren
expressions, etc.

http://reviews.llvm.org/D4416

Files:
  lib/CodeGen/CGExprCXX.cpp
  test/CodeGenCXX/typeid-should-throw.cpp

Index: lib/CodeGen/CGExprCXX.cpp
===================================================================
--- lib/CodeGen/CGExprCXX.cpp
+++ lib/CodeGen/CGExprCXX.cpp
@@ -1615,6 +1615,29 @@
   EmitBlock(DeleteEnd);
 }
 
+static bool isGLValueFromPointerDeref(const Expr *E) {
+  E = E->IgnoreParenCasts();
+
+  if (const auto *UO = dyn_cast<UnaryOperator>(E))
+    if (UO->getOpcode() == UO_Deref)
+      return true;
+
+  if (const auto *BO = dyn_cast<BinaryOperator>(E))
+    if (BO->getOpcode() == BO_Comma)
+      return isGLValueFromPointerDeref(BO->getRHS());
+
+  if (const auto *CO = dyn_cast<ConditionalOperator>(E))
+    return isGLValueFromPointerDeref(CO->getTrueExpr()) ||
+           isGLValueFromPointerDeref(CO->getFalseExpr());
+
+  if (const auto *BCO = dyn_cast<BinaryConditionalOperator>(E))
+    if (const auto *OVE = dyn_cast<OpaqueValueExpr>(BCO->getTrueExpr()))
+      return isGLValueFromPointerDeref(OVE->getSourceExpr()) ||
+             isGLValueFromPointerDeref(BCO->getFalseExpr());
+
+  return false;
+}
+
 static llvm::Value *EmitTypeidFromVTable(CodeGenFunction &CGF, const Expr *E,
                                          llvm::Type *StdTypeInfoPtrTy) {
   // Get the vtable pointer.
@@ -1624,13 +1647,9 @@
   //   If the glvalue expression is obtained by applying the unary * operator to
   //   a pointer and the pointer is a null pointer value, the typeid expression
   //   throws the std::bad_typeid exception.
-  bool IsDeref = false;
-  if (const UnaryOperator *UO = dyn_cast<UnaryOperator>(E->IgnoreParens()))
-    if (UO->getOpcode() == UO_Deref)
-      IsDeref = true;
-
   QualType SrcRecordTy = E->getType();
-  if (CGF.CGM.getCXXABI().shouldTypeidBeNullChecked(IsDeref, SrcRecordTy)) {
+  if (CGF.CGM.getCXXABI().shouldTypeidBeNullChecked(
+          isGLValueFromPointerDeref(E), SrcRecordTy)) {
     llvm::BasicBlock *BadTypeidBlock =
         CGF.createBasicBlock("typeid.bad_typeid");
     llvm::BasicBlock *EndBlock = CGF.createBasicBlock("typeid.end");
Index: test/CodeGenCXX/typeid-should-throw.cpp
===================================================================
--- /dev/null
+++ test/CodeGenCXX/typeid-should-throw.cpp
@@ -0,0 +1,44 @@
+// RUN: %clang_cc1 %s -triple %itanium_abi_triple -Wno-unused-value -emit-llvm -o - | FileCheck %s
+namespace std {
+struct type_info;
+}
+
+struct A {
+  virtual ~A();
+};
+struct B : A {};
+
+void f1(A *x) { typeid(false, *x); }
+// CHECK-LABEL: define void @_Z2f1P1A
+// CHECK:       icmp eq {{.*}}, null
+// CHECK-NEXT:  br i1
+
+void f2(bool b, A *x, A *y) { typeid(b ? *x : *y); }
+// CHECK-LABEL: define void @_Z2f2bP1AS0_
+// CHECK:       icmp eq {{.*}}, null
+// CHECK-NEXT:  br i1
+
+void f3(bool b, A *x, A &y) { typeid(b ? *x : y); }
+// CHECK-LABEL: define void @_Z2f3bP1ARS_
+// CHECK:       icmp eq {{.*}}, null
+// CHECK-NEXT:  br i1
+
+void f4(bool b, A &x, A *y) { typeid(b ? x : *y); }
+// CHECK-LABEL: define void @_Z2f4bR1APS_
+// CHECK:       icmp eq {{.*}}, null
+// CHECK-NEXT:  br i1
+
+void f5(volatile A *x) { typeid(*x); }
+// CHECK-LABEL: define void @_Z2f5PV1A
+// CHECK:       icmp eq {{.*}}, null
+// CHECK-NEXT:  br i1
+
+void f6(A *x) { typeid((B &)*(B *)x); }
+// CHECK-LABEL: define void @_Z2f6P1A
+// CHECK:       icmp eq {{.*}}, null
+// CHECK-NEXT:  br i1
+
+void f7(A *x) { typeid((*x)); }
+// CHECK-LABEL: define void @_Z2f7P1A
+// CHECK:       icmp eq {{.*}}, null
+// CHECK-NEXT:  br i1
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