Implement bad cast checks using control flow integrity information.

[pcc]

Summary

This scheme checks that pointer and lvalue casts are made to an object of
the correct dynamic type; that is, the dynamic type of the object must be
a derived class of the pointee type of the cast. The checks are currently
only introduced where the class being casted to is a polymorphic class.

[jfb]

docs/UsersManual.rst

974

Add -fsanitize=cfi-cast-strict?

lib/CodeGen/CGClass.cpp

2121

Why?

test/CodeGenCXX/cfi-cast.cpp

4

Could you have a quick blurb that helps decipher the metadata !"1B' part, explaining that it's the important bit in the checks.

15

CHECK-LABEL-DCAST (same below).

77

Add rvalue ref test?

A a();

B rvalue() {
  return static_cast<B&&>(a());
}

[kcc]

Please also add compiler-rt test(s)

docs/UsersManual.rst

971

Don't we want more verbose names?
cfi-polymorphic-base-downcast
cfi-void-to-polymorphic-cast
or something.

[pcc]

• Address reviewer comments

[pcc]

Please also add compiler-rt test(s)

Will do

docs/UsersManual.rst

971

Okay, I've given these better names.

974

Done.

lib/CodeGen/CGClass.cpp

2121

Explained in comment.

test/CodeGenCXX/cfi-cast.cpp

4

Done

15

Done

77

Done.

[jfb]

lgtm after what seems like a typo.

test/CodeGenCXX/cfi-cast.cpp

59

B&&

docs/ControlFlowIntegrity.rst

 A performance overhead of less than 1% has been measured by running the
 Dromaeo benchmark suite against an instrumented version of the Chromium
 web browser. Another good performance benchmark for this mechanism is the
 virtual-call-heavy SPEC 2006 xalancbmk.
 
 Note that this scheme has not yet been optimized for binary size; an increase
 of up to 15% has been observed for Chromium.
 
+Bad Cast Checking
+-----------------
+
+This scheme checks that pointer casts are made to an object of the correct
+dynamic type; that is, the dynamic type of the object must be a derived class
+of the pointee type of the cast. The checks are currently only introduced
+where the class being casted to is a polymorphic class.
+
+Bad casts are not in themselves control flow integrity violations, but they
+can also create security vulnerabilities, and the implementation uses many
+of the same mechanisms.
+
+There are two types of bad cast that may be forbidden: bad casts from a base
+class to a derived class (which can be checked with ``-fsanitize=cfi-dcast``),
+and bad casts from a pointer of type ``void*`` or another unrelated type
+(which can be checked with ``-fsanitize=cfi-vcast``).
+
+The difference between these two types of casts is that the first is defined
+by the C++ standard to produce an undefined value, while the second is not
+in itself undefined behavior (it is well defined to cast the pointer back
+to its original type).
+
+If a program as a matter of policy forbids the second type of cast, that
+restriction can normally be enforced. However it may in some cases be necessary
+for a function to perform a forbidden cast to conform with an external API
+(e.g. the ``allocate`` member function of a standard library allocator). Such
+functions may be blacklisted using a :doc:`SanitizerSpecialCaseList`.
+
+For this scheme to work, all translation units containing the definition
+of a virtual member function (whether inline or not) must be compiled with
+``-fsanitize=cfi-dcast`` or ``-fsanitize=cfi-vcast`` enabled and be statically
+linked into the program. Classes in the C++ standard library (under namespace
+``std``) are exempted from checking, and therefore programs may be linked
+against a pre-built standard library, but this may change in the future.
+
+Strictness
+~~~~~~~~~~
+
+If a class has a single non-virtual base and does not introduce or override
+virtual member functions or fields other than an implicitly defined virtual
+destructor, it will have the same layout and virtual function semantics as
+its base. By default, casts to such classes are checked as if they were made
+to the least derived such class.
+
+Casting an instance of a base class to such a derived class is technically
+undefined behavior, but it is a relatively common hack for introducing
+member functions on class instances with specific properties that works under
+most compilers and should not have security implications, so we allow it by
+default. It can be disabled with ``-fsanitize=cfi-cast-strict``.
+
 Design
 ------
 
 Please refer to the :doc:`design document<ControlFlowIntegrityDesign>`.
 
 Publications
 ------------
 
 `Control-Flow Integrity: Principles, Implementations, and Applications <http://research.microsoft.com/pubs/64250/ccs05.pdf>`_.
 Martin Abadi, Mihai Budiu, Úlfar Erlingsson, Jay Ligatti.
 
 `Enforcing Forward-Edge Control-Flow Integrity in GCC & LLVM <http://www.pcc.me.uk/~peter/acad/usenix14.pdf>`_.
 Caroline Tice, Tom Roeder, Peter Collingbourne, Stephen Checkoway,
 Úlfar Erlingsson, Luis Lozano, Geoff Pike.

docs/UsersManual.rst

**-f[no-]sanitize=check1,check2,...**
    The following more fine-grained checks are also available:
 
    -  ``-fsanitize=alignment``: Use of a misaligned pointer or creation
       of a misaligned reference.
    -  ``-fsanitize=bool``: Load of a ``bool`` value which is neither
       ``true`` nor ``false``.
    -  ``-fsanitize=bounds``: Out of bounds array indexing, in cases
       where the array bound can be statically determined.
+   -  ``-fsanitize=cfi-dcast``: Base-to-derived cast to the wrong
+      dynamic type. Implies ``-flto``.
+   -  ``-fsanitize=cfi-vcast``: Cast from ``void*`` or another unrelated
+      type to the wrong dynamic type. Implies ``-flto``.
    -  ``-fsanitize=cfi-vptr``: Use of an object whose vptr is of the
       wrong dynamic type. Implies ``-flto``.
    -  ``-fsanitize=enum``: Load of a value of an enumerated type which
       is not in the range of representable values for that enumerated
       type.
    -  ``-fsanitize=float-cast-overflow``: Conversion to, from, or
       between floating-point types which would overflow the
       destination.

include/clang/Basic/Sanitizers.def

 
 // IntegerSanitizer
 SANITIZER("unsigned-integer-overflow", UnsignedIntegerOverflow)
 
 // DataFlowSanitizer
 SANITIZER("dataflow", DataFlow)
 
 // Control Flow Integrity
+SANITIZER("cfi-cast-strict", CFICastStrict)
+SANITIZER("cfi-dcast", CFIDCast)
+SANITIZER("cfi-vcast", CFIVCast)
 SANITIZER("cfi-vptr", CFIVptr)
-SANITIZER_GROUP("cfi", CFI, CFIVptr)
+SANITIZER_GROUP("cfi", CFI, CFIDCast | CFIVCast | CFIVptr)
 
 // -fsanitize=undefined-trap includes sanitizers from -fsanitize=undefined
 // that can be used without runtime support, generally by providing extra
 // -fsanitize-undefined-trap-on-error flag.
 SANITIZER_GROUP("undefined-trap", UndefinedTrap,
                 Alignment | Bool | ArrayBounds | Enum | FloatCastOverflow |
                     FloatDivideByZero | IntegerDivideByZero | NonnullAttribute |
                     Null | ObjectSize | Return | ReturnsNonnullAttribute |

lib/CodeGen/CGClass.cpp

llvm::Value *CodeGenFunction::GetVTablePtr(llvm::Value *This,
   return VTable;
 }
 
 void CodeGenFunction::EmitVTablePtrCheckForCall(const CXXMethodDecl *MD,
                                                 llvm::Value *VTable) {
   if (!SanOpts.has(SanitizerKind::CFIVptr))
     return;
 
-  const CXXRecordDecl *RD = MD->getParent();
+  EmitVTablePtrCheck(MD->getParent(), VTable);
+}
+
+// If a class has a single non-virtual base and does not introduce or override
+// virtual member functions or fields, it will have the same layout as its base.
+// This function returns the least derived such class.
+//
+// Casting an instance of a base class to such a derived class is technically
+// undefined behavior, but it is a relatively common hack for introducing member
+// functions on class instances with specific properties (e.g. llvm::Operator)
+// that works under most compilers and should not have security implications, so
+// we allow it by default. It can be disabled with -fsanitize=cfi-cast-strict.
+static const CXXRecordDecl *
+LeastDerivedClassWithSameLayout(const CXXRecordDecl *RD) {
+  if (!RD->field_empty())
+    return RD;
+
+  if (RD->getNumVBases() != 0)
+    return RD;
+
+  if (RD->getNumBases() != 1)
+    return RD;
+
+  for (const CXXMethodDecl *MD : RD->methods()) {
+    if (MD->isVirtual()) {
+      // Virtual member functions are only ok if they are implicit destructors.
+      if (isa<CXXDestructorDecl>(MD) && MD->isImplicit())
+        continue;
+      return RD;
+    }
+  }
+
+  return LeastDerivedClassWithSameLayout(
+      RD->bases_begin()->getType()->getAsCXXRecordDecl());
+}
+
+void CodeGenFunction::EmitVTablePtrCheckForCast(QualType T,
+                                                llvm::Value *Derived,
+                                                bool MayBeNull) {
+  if (!getLangOpts().CPlusPlus)
+    return;
+
+  auto *ClassTy = T->getAs<RecordType>();
+  if (!ClassTy)
+    return;
+
+  const CXXRecordDecl *ClassDecl = cast<CXXRecordDecl>(ClassTy->getDecl());
+
+  if (!ClassDecl->isCompleteDefinition() || !ClassDecl->isDynamicClass())
+    return;
+
+  SmallString<64> MangledName;
+  llvm::raw_svector_ostream Out(MangledName);
+  CGM.getCXXABI().getMangleContext().mangleCXXRTTI(T.getUnqualifiedType(),
+                                                   Out);
+
+  // Blacklist based on the mangled type.
+  if (CGM.getContext().getSanitizerBlacklist().isBlacklistedType(Out.str()))
+    return;
+
+  if (!SanOpts.has(SanitizerKind::CFICastStrict))
+    ClassDecl = LeastDerivedClassWithSameLayout(ClassDecl);
+
+  llvm::BasicBlock *ContBlock = 0;
+
+  if (MayBeNull) {
+    llvm::Value *DerivedNotNull =
+        Builder.CreateIsNotNull(Derived, "cast.nonnull");
+
+    llvm::BasicBlock *CheckBlock = createBasicBlock("cast.check");
+    ContBlock = createBasicBlock("cast.cont");
+
+    Builder.CreateCondBr(DerivedNotNull, CheckBlock, ContBlock);
+
+    EmitBlock(CheckBlock);
+  }
+
+  llvm::Value *VTable = GetVTablePtr(Derived, Int8PtrTy);
+  EmitVTablePtrCheck(ClassDecl, VTable);
+
+  if (MayBeNull) {
+    Builder.CreateBr(ContBlock);
+    EmitBlock(ContBlock);
+  }
+}
+
+void CodeGenFunction::EmitVTablePtrCheck(const CXXRecordDecl *RD,
+                                         llvm::Value *VTable) {
   // FIXME: Add blacklisting scheme.
   if (RD->isInStdNamespace())
     return;
 
   std::string OutName;
   llvm::raw_string_ostream Out(OutName);
   CGM.getCXXABI().getMangleContext().mangleCXXVTableBitSet(RD, Out);
 

lib/CodeGen/CGExpr.cpp

llvm::Value *Derived =
                                /*NullCheckValue=*/false);
 
     // C++11 [expr.static.cast]p2: Behavior is undefined if a downcast is
     // performed and the object is not of the derived type.
     if (sanitizePerformTypeCheck())
       EmitTypeCheck(TCK_DowncastReference, E->getExprLoc(),
                     Derived, E->getType());
 
+    if (SanOpts.has(SanitizerKind::CFIDCast))
+      EmitVTablePtrCheckForCast(E->getType(), Derived, /*MayBeNull=*/false);
+
     return MakeAddrLValue(Derived, E->getType());
   }
   case CK_LValueBitCast: {
     // This must be a reinterpret_cast (or c-style equivalent).
     const auto *CE = cast<ExplicitCastExpr>(E);
 
     LValue LV = EmitLValue(E->getSubExpr());
     llvm::Value *V = Builder.CreateBitCast(LV.getAddress(),
                                            ConvertType(CE->getTypeAsWritten()));
+
+    if (SanOpts.has(SanitizerKind::CFIVCast))
+      EmitVTablePtrCheckForCast(E->getType(), V, /*MayBeNull=*/false);
+
     return MakeAddrLValue(V, E->getType());
   }
   case CK_ObjCObjectLValueCast: {
     LValue LV = EmitLValue(E->getSubExpr());
     QualType ToType = getContext().getLValueReferenceType(E->getType());
     llvm::Value *V = Builder.CreateBitCast(LV.getAddress(),
                                            ConvertType(ToType));
     return MakeAddrLValue(V, E->getType());

lib/CodeGen/CGExprScalar.cpp

case CK_BitCast: {
     Value *Src = Visit(const_cast<Expr*>(E));
     llvm::Type *SrcTy = Src->getType();
     llvm::Type *DstTy = ConvertType(DestTy);
     if (SrcTy->isPtrOrPtrVectorTy() && DstTy->isPtrOrPtrVectorTy() &&
         SrcTy->getPointerAddressSpace() != DstTy->getPointerAddressSpace()) {
       llvm_unreachable("wrong cast for pointers in different address spaces"
                        "(must be an address space cast)!");
     }
+
+    if (CGF.SanOpts.has(SanitizerKind::CFIVCast)) {
+      if (auto PT = DestTy->getAs<PointerType>())
+        CGF.EmitVTablePtrCheckForCast(PT->getPointeeType(), Src,
+                                      /*MayBeNull=*/true);
+    }
+
     return Builder.CreateBitCast(Src, DstTy);
   }
   case CK_AddressSpaceConversion: {
     Value *Src = Visit(const_cast<Expr*>(E));
     return Builder.CreateAddrSpaceCast(Src, ConvertType(DestTy));
   }
   case CK_AtomicToNonAtomic:
   case CK_NonAtomicToAtomic:
llvm::Value *Derived =
                                    ShouldNullCheckClassCastValue(CE));
 
     // C++11 [expr.static.cast]p11: Behavior is undefined if a downcast is
     // performed and the object is not of the derived type.
     if (CGF.sanitizePerformTypeCheck())
       CGF.EmitTypeCheck(CodeGenFunction::TCK_DowncastPointer, CE->getExprLoc(),
                         Derived, DestTy->getPointeeType());
 
+    if (CGF.SanOpts.has(SanitizerKind::CFIDCast))
+      CGF.EmitVTablePtrCheckForCast(DestTy->getPointeeType(), Derived,
+                                    /*MayBeNull=*/true);
+
     return Derived;
   }
   case CK_UncheckedDerivedToBase:
   case CK_DerivedToBase: {
     const CXXRecordDecl *DerivedClassDecl =
       E->getType()->getPointeeCXXRecordDecl();
     assert(DerivedClassDecl && "DerivedToBase arg isn't a C++ object pointer!");
 

lib/CodeGen/CodeGenFunction.h

void InitializeVTablePointers(BaseSubobject Base,
                                 VisitedVirtualBasesSetTy& VBases);
 
   void InitializeVTablePointers(const CXXRecordDecl *ClassDecl);
 
   /// GetVTablePtr - Return the Value of the vtable pointer member pointed
   /// to by This.
   llvm::Value *GetVTablePtr(llvm::Value *This, llvm::Type *Ty);
 
+  /// \brief Derived is the presumed address of an object of type T after a
+  /// cast. If T is a polymorphic class type, emit a check that the virtual
+  /// table for Derived belongs to a class derived from T.
+  void EmitVTablePtrCheckForCast(QualType T, llvm::Value *Derived,
+                                 bool MayBeNull);
+
   /// EmitVTablePtrCheckForCall - Virtual method MD is being called via VTable.
   /// If vptr CFI is enabled, emit a check that VTable is valid.
   void EmitVTablePtrCheckForCall(const CXXMethodDecl *MD, llvm::Value *VTable);
 
+  /// EmitVTablePtrCheck - Emit a check that VTable is a valid virtual table for
+  /// RD using llvm.bitset.test.
+  void EmitVTablePtrCheck(const CXXRecordDecl *RD, llvm::Value *VTable);
+
   /// CanDevirtualizeMemberFunctionCalls - Checks whether virtual calls on given
   /// expr can be devirtualized.
   bool CanDevirtualizeMemberFunctionCall(const Expr *Base,
                                          const CXXMethodDecl *MD);
 
   /// EnterDtorCleanups - Enter the cleanups necessary to complete the
   /// given phase of destruction for a destructor.  The end result
   /// should call destructors on members and base classes in reverse

lib/Driver/SanitizerArgs.cpp

#include "clang/Basic/Sanitizers.def"
   NeedsUbsanRt = Undefined | Integer,
   NotAllowedWithTrap = Vptr,
   RequiresPIE = Memory | DataFlow,
   NeedsUnwindTables = Address | Thread | Memory | DataFlow,
   SupportsCoverage = Address | Memory | Leak | Undefined | Integer,
   RecoverableByDefault = Undefined | Integer,
   Unrecoverable = Address | Unreachable | Return,
   LegacyFsanitizeRecoverMask = Undefined | Integer,
-  NeedsLTO = CFIVptr,
+  NeedsLTO = CFIDCast | CFIVCast | CFIVptr,
 };
 }
 
 /// Returns true if set of \p Sanitizers contain at least one sanitizer from
 /// \p Kinds.
 static bool hasOneOf(const clang::SanitizerSet &Sanitizers, uint64_t Kinds) {
 #define SANITIZER(NAME, ID)                                                    \
   if (Sanitizers.has(clang::SanitizerKind::ID) && (Kinds & ID))                \
bool SanitizerArgs::requiresPIE() const {
   return AsanZeroBaseShadow || hasOneOf(Sanitizers, RequiresPIE);
 }
 
 bool SanitizerArgs::needsUnwindTables() const {
   return hasOneOf(Sanitizers, NeedsUnwindTables);
 }
 
 bool SanitizerArgs::needsLTO() const {
-  return hasOneOf(Sanitizers, CFIVptr);
+  return hasOneOf(Sanitizers, NeedsLTO);
 }
 
 void SanitizerArgs::clear() {
   Sanitizers.clear();
   RecoverableSanitizers.clear();
   BlacklistFiles.clear();
   SanitizeCoverage = 0;
   MsanTrackOrigins = 0;

test/CodeGenCXX/cfi-cast.cpp

+// RUN: %clang_cc1 -triple x86_64-unknown-linux -fsanitize=cfi-dcast -emit-llvm -o - %s | FileCheck -check-prefix=CHECK-DCAST %s
+// RUN: %clang_cc1 -triple x86_64-unknown-linux -fsanitize=cfi-vcast -emit-llvm -o - %s | FileCheck -check-prefix=CHECK-VCAST %s
+// RUN: %clang_cc1 -triple x86_64-unknown-linux -fsanitize=cfi-vcast,cfi-cast-strict -emit-llvm -o - %s | FileCheck -check-prefix=CHECK-VCAST-STRICT %s
+
+struct A {
+  virtual void f();
+};
+
+struct B : A {
+  virtual void f();
+};
+
+struct C : A {};
+
+// CHECK-DCAST: define void @_Z3abpP1A
+void abp(A *a) {
+  // CHECK-DCAST: [[P:%[^ ]*]] = call i1 @llvm.bitset.test(i8* {{%[^ ]*}}, metadata !"1B")
+  // CHECK-DCAST-NEXT: br i1 [[P]], label %[[CONTBB:[^ ]*]], label %[[TRAPBB:[^ ]*]]
+
+  // CHECK-DCAST: [[TRAPBB]]
+  // CHECK-DCAST-NEXT: call void @llvm.trap()
+  // CHECK-DCAST-NEXT: unreachable
+
+  // CHECK-DCAST: [[CONTBB]]
+  // CHECK-DCAST: ret
+  static_cast<B*>(a);
+}
+
+// CHECK-DCAST: define void @_Z3abrR1A
+void abr(A &a) {
+  // CHECK-DCAST: [[P:%[^ ]*]] = call i1 @llvm.bitset.test(i8* {{%[^ ]*}}, metadata !"1B")
+  // CHECK-DCAST-NEXT: br i1 [[P]], label %[[CONTBB:[^ ]*]], label %[[TRAPBB:[^ ]*]]
+
+  // CHECK-DCAST: [[TRAPBB]]
+  // CHECK-DCAST-NEXT: call void @llvm.trap()
+  // CHECK-DCAST-NEXT: unreachable
+
+  // CHECK-DCAST: [[CONTBB]]
+  // CHECK-DCAST: ret
+  static_cast<B&>(a);
+}
+
+// CHECK-VCAST: define void @_Z3vbpPv
+void vbp(void *p) {
+  // CHECK-VCAST: [[P:%[^ ]*]] = call i1 @llvm.bitset.test(i8* {{%[^ ]*}}, metadata !"1B")
+  // CHECK-VCAST-NEXT: br i1 [[P]], label %[[CONTBB:[^ ]*]], label %[[TRAPBB:[^ ]*]]
+
+  // CHECK-VCAST: [[TRAPBB]]
+  // CHECK-VCAST-NEXT: call void @llvm.trap()
+  // CHECK-VCAST-NEXT: unreachable
+
+  // CHECK-VCAST: [[CONTBB]]
+  // CHECK-VCAST: ret
+  static_cast<B*>(p);
+}
+
+// CHECK-VCAST: define void @_Z3vbrRc
+void vbr(char &r) {
+  // CHECK-VCAST: [[P:%[^ ]*]] = call i1 @llvm.bitset.test(i8* {{%[^ ]*}}, metadata !"1B")
+  // CHECK-VCAST-NEXT: br i1 [[P]], label %[[CONTBB:[^ ]*]], label %[[TRAPBB:[^ ]*]]
+
+  // CHECK-VCAST: [[TRAPBB]]
+  // CHECK-VCAST-NEXT: call void @llvm.trap()
+  // CHECK-VCAST-NEXT: unreachable
+
+  // CHECK-VCAST: [[CONTBB]]
+  // CHECK-VCAST: ret
+  reinterpret_cast<B&>(r);
+}
+
+// CHECK-VCAST: define void @_Z3vcpPv
+// CHECK-VCAST-STRICT: define void @_Z3vcpPv
+void vcp(void *p) {
+  // CHECK-VCAST: [[P:%[^ ]*]] = call i1 @llvm.bitset.test(i8* {{%[^ ]*}}, metadata !"1A")
+  // CHECK-VCAST-STRICT: [[P:%[^ ]*]] = call i1 @llvm.bitset.test(i8* {{%[^ ]*}}, metadata !"1C")
+  static_cast<C*>(p);
+}

test/Driver/fsanitize.c

 
 // RUN: %clang -target x86_64-apple-darwin10 -fsanitize=function %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-FSAN-DARWIN
 // CHECK-FSAN-DARWIN: unsupported option '-fsanitize=function' for target 'x86_64-apple-darwin10'
 
 // RUN: %clang -target x86_64-apple-darwin10 -fsanitize=function -fsanitize=undefined %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-FSAN-UBSAN-DARWIN
 // CHECK-FSAN-UBSAN-DARWIN: unsupported option '-fsanitize=function' for target 'x86_64-apple-darwin10'
 
 // RUN: %clang -target x86_64-linux-gnu -fsanitize=cfi -c %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-CFI
-// RUN: %clang -target x86_64-linux-gnu -fsanitize=cfi-vptr -c %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-CFI
-// CHECK-CFI: -emit-llvm-bc{{.*}}-fsanitize=cfi-vptr
+// RUN: %clang -target x86_64-linux-gnu -fsanitize=cfi-dcast -c %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-CFI-DCAST
+// RUN: %clang -target x86_64-linux-gnu -fsanitize=cfi-vcast -c %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-CFI-VCAST
+// RUN: %clang -target x86_64-linux-gnu -fsanitize=cfi-vptr -c %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-CFI-VPTR
+// CHECK-CFI: -emit-llvm-bc{{.*}}-fsanitize=cfi-dcast,cfi-vcast,cfi-vptr
+// CHECK-CFI-DCAST: -emit-llvm-bc{{.*}}-fsanitize=cfi-dcast
+// CHECK-CFI-VCAST: -emit-llvm-bc{{.*}}-fsanitize=cfi-vcast
+// CHECK-CFI-VPTR: -emit-llvm-bc{{.*}}-fsanitize=cfi-vptr
 
 // RUN: %clang_cl -fsanitize=address -c -MDd -### -- %s 2>&1 | FileCheck %s -check-prefix=CHECK-ASAN-DEBUGRTL
 // RUN: %clang_cl -fsanitize=address -c -MTd -### -- %s 2>&1 | FileCheck %s -check-prefix=CHECK-ASAN-DEBUGRTL
 // RUN: %clang_cl -fsanitize=address -c -LDd -### -- %s 2>&1 | FileCheck %s -check-prefix=CHECK-ASAN-DEBUGRTL
 // RUN: %clang_cl -fsanitize=address -c -MD -MDd -### -- %s 2>&1 | FileCheck %s -check-prefix=CHECK-ASAN-DEBUGRTL
 // RUN: %clang_cl -fsanitize=address -c -MT -MTd -### -- %s 2>&1 | FileCheck %s -check-prefix=CHECK-ASAN-DEBUGRTL
 // RUN: %clang_cl -fsanitize=address -c -LD -LDd -### -- %s 2>&1 | FileCheck %s -check-prefix=CHECK-ASAN-DEBUGRTL
 // CHECK-ASAN-DEBUGRTL: error: invalid argument