Rein ubsan's vptr sanitizer back a bit. Per core issue 453, binding a reference

to an object outside its lifetime does not have undefined behavior.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@170387 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/CGExpr.cpp

@@ -538,8 +538,15 @@ void CodeGenFunction::EmitTypeCheck(TypeCheckKind TCK, SourceLocation Loc,
 
   // If possible, check that the vptr indicates that there is a subobject of
   // type Ty at offset zero within this object.
+  //
+  // C++11 [basic.life]p5,6:
+  //   [For storage which does not refer to an object within its lifetime]
+  //   The program has undefined behavior if:
+  //    -- the [pointer or glvalue] is used to access a non-static data member
+  //       or call a non-stastic member function
   CXXRecordDecl *RD = Ty->getAsCXXRecordDecl();
-  if (getLangOpts().SanitizeVptr && TCK != TCK_ConstructorCall &&
+  if (getLangOpts().SanitizeVptr &&
+      (TCK == TCK_MemberAccess || TCK == TCK_MemberCall) &&
       RD && RD->hasDefinition() && RD->isDynamicClass()) {
     // Compute a hash of the mangled name of the type.
     //

test/CodeGenCXX/catch-undef-behavior.cpp

@@ -1,7 +1,13 @@
 // RUN: %clang_cc1 -fsanitize=signed-integer-overflow,integer-divide-by-zero,float-divide-by-zero,shift,unreachable,return,vla-bound,alignment,null,vptr,object-size,float-cast-overflow,bool,enum -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s
 
+struct S {
+  double d;
+  int a, b;
+  virtual int f();
+};
+
 // CHECK: @_Z17reference_binding
-void reference_binding(int *p) {
+void reference_binding(int *p, S *q) {
   // C++ core issue 453: If an lvalue to which a reference is directly bound
   // designates neither an existing object or function of an appropriate type,
   // nor a region of storage of suitable size and alignment to contain an object
@@ -16,13 +22,11 @@ void reference_binding(int *p) {
   // CHECK-NEXT: %[[MISALIGN:.*]] = and i64 %[[PTRINT]], 3
   // CHECK-NEXT: icmp eq i64 %[[MISALIGN]], 0
   int &r = *p;
-}
 
-struct S {
-  double d;
-  int a, b;
-  virtual int f();
-};
+  // A reference is not required to refer to an object within its lifetime.
+  // CHECK-NOT: __ubsan_handle_dynamic_type_cache_miss
+  S &r2 = *q;
+}
 
 // CHECK: @_Z13member_access
 void member_access(S *p) {