[Sema] Change addr space diagnostics in casts to follow C++ style

[Anastasia]

Summary

This patch adds a new diagnostic for mismatching address spaces to be used for C++ casts (TODO: only enabled in C style cast for now, the rest will follow!).

This change extends C-style cast rules to account for address spaces. It also adds a separate function for address space cast checking that can be used to map from a separate address space cast operator addrspace_cast (to be added as a follow up patch).

Note, that after this change clang will no longer allows arbitrary address space conversions in reinterpret_casts because they can lead to accidental errors. The implicit safe conversions would still be allowed.

See RFC for more details: http://lists.llvm.org/pipermail/cfe-dev/2018-December/060546.html

[ebevhan]

lib/Sema/SemaCast.cpp

2224

This might not be applicable to this patch, but just something I noticed.

So reinterpret_cast only operates on pointers when dealing with address spaces. What about something like

T a;
T& a_ref = reinterpret_cast<T&>(a);

reinterpret_cast on an lvalue like this is equivalent to *reinterpret_cast<T*>(&a). So for AS code:

__private T x;
__generic T& ref = reinterpret_cast<__generic T&>(x);

This should work, since *reinterpret_cast<__generic T*>(&x) is valid, correct?

What if we have the reference cast case with a different address space like this? Doesn't the IsLValueCast check need to be first?

2309

Maybe I'm mistaken, but won't getting the canonical type here drop qualifiers (like cv) in nested pointers? If so, an addrspace_cast might strip qualifiers by mistake.

[Anastasia]

lib/Sema/SemaCast.cpp

2224

What if we have the reference cast case with a different address space like this? Doesn't the IsLValueCast check need to be first?

Ok, let me see if I understand you. I changed __generic -> __global since it's invalid and the error is produced as follows:

test.cl:7:21: error: reinterpret_cast from 'int' to '__global int &' is not allowed
__global int& ref = reinterpret_cast<__global int&>(x);

Is this not what we are expecting here?

2309

Yes, indeed I will need to extend this to nested pointers when we are ready. But for now I can try to change this bit... however I am not sure it will work w/o canonical types when we have typedef. I will try to create an example and see.

[ebevhan]

lib/Sema/SemaCast.cpp

2224

My last sentence could have been a bit clearer. Yes, for the __private->__global case, it should error. But I was thinking more of the case where the AS conversion is valid, like __private->__generic. Then we will do the AS conversion, but we should have done both an AS conversion and an LValueBitCast, because we need to both convert the 'pointer' and also dereference it.

[Anastasia]

lib/Sema/SemaCast.cpp

2224

Hmm... it seems like here we can only have one cast kind... I guess CK_LValueBitCast leads to the generation of bitcast in the IR? But addrspacecast can perform both bit reinterpretation and address translation, so perhaps it makes sense to only have an address space conversion in this case? Unless some other logic is needed elsewhere before CodeGen... I will try to construct a test case in plain C++.

[Anastasia]

lib/Sema/SemaCast.cpp

2309

I checked the canonical type does preserve the qualifiers correctly.

Here is the AST dump of the following C type mytype const __generic* where typedef __generic int* mytype;.

PointerType 0x204d3b0 'const __generic mytype *'
`-QualType 0x204d369 'const __generic mytype' const __generic
  `-TypedefType 0x204d320 'mytype' sugar
    |-Typedef 0x204d1b0 'mytype'
    `-PointerType 0x204d170 '__generic int *'
      `-QualType 0x204d158 '__generic int' __generic
        `-BuiltinType 0x2009750 'int'

and it's canonical representation in AST is:

PointerType 0x204d380 '__generic int *const __generic *'
`-QualType 0x204d349 '__generic int *const __generic' const __generic
  `-PointerType 0x204d170 '__generic int *'
    `-QualType 0x204d158 '__generic int' __generic
      `-BuiltinType 0x2009750 'int'

So using canonical type will just simply handling of nested pointer chain by avoiding special casing typedefs. We won't loose any qualifiers.

[ebevhan]

lib/Sema/SemaCast.cpp

2224

Hmm... it seems like here we can only have one cast kind... I guess CK_LValueBitCast leads to the generation of bitcast in the IR?

That's likely, yes. The dereference in the example disappears if we assign to a T& and it becomes implied if we assign to a T through lvalue-to-rvalue conversion, so in both cases we're taking the address of something and then converting the address to a different type.

But addrspacecast can perform both bit reinterpretation and address translation, so perhaps it makes sense to only have an address space conversion in this case? Unless some other logic is needed elsewhere before CodeGen... I will try to construct a test case in plain C++.

Oh, you're right! For some reason I was thinking that addrspacecast could only change the addrspace of the argument, but apparently it could change the pointee type too. At least according to the langref. So long as nothing in Clang assumes that a CK_AddressSpaceConversion can't change the pointee type as well as the address space I guess it should be safe.

When I try a 'simultaneous' conversion in C, I don't get a single addrspacecast, though: https://godbolt.org/z/Q818yW So I wonder if existing code handles this.

A test case would be good.

2309

Okay, seems good then!

[Anastasia]

lib/Sema/SemaCast.cpp

2224

I am not sure I understood the problem you are describing, may be I need an example...

But the valid address space conversion example in OpenCL

__private T x = ...;
__generic T& ref = reinterpret_cast<__generic T&>(x);

produces correctly addrspacecast

%0 = load i32*, i32** %x.addr, align 4
%1 = addrspacecast i32* %0 to i32 addrspace(4)*
store i32 addrspace(4)* %1, i32 addrspace(4)** %ref

However, if we keep checking CK_LValueBitCast first clang attempts to generate bitcast but fails because pointers are in different address spaces.

[Anastasia]

lib/Sema/SemaCast.cpp

2224

Sorry, I haven't seen your previous comment before sending mine. :)

When I try a 'simultaneous' conversion in C, I don't get a single addrspacecast

I think 2 conversions in IR are not necessary, not sure how we ended up doing this though... but we had related discussion on that while implementing some OpenCL features and the conclusion was that we should just have an addrspacecast. Do you think we should correct this in C?

When I try a 'simultaneous' conversion in C, I don't get a single addrspacecast, though: https://godbolt.org/z/Q818yW So I wonder if existing code handles this.

Ok, I will check whether we cover this with any CodeGen test and if not I will add one.

[ebevhan]

lib/Sema/SemaCast.cpp

2224

I think 2 conversions in IR are not necessary, not sure how we ended up doing this though... but we had related discussion on that while implementing some OpenCL features and the conclusion was that we should just have an addrspacecast. Do you think we should correct this in C?

Yes, I don't think it's necessary either, the addrspacecast should be enough.

Looking closer at the emission in the C case, Clang actually emits a single addrspacecast. Something else in LLVM is splitting it up into an addrspacecast and a bitcast. So it seems to be working just fine.

I was just concerned that we might hit edge cases where one conversion wasn't enough to convert both the address space and the pointee type, but it seems like CK_AddressSpaceConversion acts as both if it needs to. So it all seems good!

[Anastasia]

Added a CodeGen test to cover address space of reference in reinterpret_cast.

[rjmccall]

One comment, but otherwise LGTM.

lib/Sema/SemaCast.cpp

2309

It seems to me that the rules in this function are the reasonable cross-language rules. If you want to check for OpenCL at the top as a fast-path check (taking advantage of that fact that no other language modes currently have overlapping address spaces), that might be reasonable, but the comment and indentation should reflect that.

[Anastasia]

• Added a comment to explain OpenCL check.

[Anastasia]

lib/Sema/SemaCast.cpp

2309

Btw, I attempted to remove the OpenCL check and unfortunately found failure in the following test: test/CodeGenCXX/address-space-cast.cpp

error: C-style cast from 'char *' to '__attribute__((address_space(5))) char *' converts between mismatching address spaces
  __private__ char *priv_char_ptr = (__private__ char *)gen_char_ptr;

I am not sure what such conversion does but I feel if I want to update it I might need to get wider agreement. I think sending an RFC might be a good way forward.

[ebevhan]

lib/Sema/SemaCast.cpp

2309

Seems like that would happen if the address spaces don't overlap, which none of the target address spaces do. That sort of cast works in C because the ASes are only tested for compatibility when you're building for OpenCL (in SemaCast:checkAddressSpaceCast). Without a guard on OpenCL, any target AS compatibility check will fail.

A possible fix could be to omit the isAddressSpaceOverlapping check when !OpenCL, but properly formalizing the AS conversion behavior would most likely be the best fix for this.

[Anastasia]

lib/Sema/SemaCast.cpp

2309

Ok yes, I would like to formalize this indeed, but I will definitely need some help. I think the best way to proceed is to gather all the ideas we have discussed so far and send an RFC.

[rjmccall]

Hmm. Yeah, Embedded C allows these casts, so contra my previous comment, I think we can't make them ill-formed outside of OpenCL mode.

[Anastasia]

In D58346#1413863, @rjmccall wrote:

Hmm. Yeah, Embedded C allows these casts, so contra my previous comment, I think we can't make them ill-formed outside of OpenCL mode.

Ok, would these rules apply in regular C99 mode then? Do you think I should change anything in the comment about the addr space cast logic here?

[rjmccall]

In the abstract, it would be nice to warn about casts that always have UB because the address spaces don't overlap; however, I'm worried about how people might be using address spaces in strange ways today, knowing that they *do* overlap, only in ways that the compiler isn't smart enough for. I think we should just be permissive in non-OpenCL mode.

[Anastasia]

Updated FiXME explaining why C++ mode is more permissive.

[Anastasia]

In D58346#1417983, @rjmccall wrote:

In the abstract, it would be nice to warn about casts that always have UB because the address spaces don't overlap; however, I'm worried about how people might be using address spaces in strange ways today, knowing that they *do* overlap, only in ways that the compiler isn't smart enough for. I think we should just be permissive in non-OpenCL mode.

Ok, I have explained this in FIXME.

[rjmccall]

lib/Sema/SemaCast.cpp

2293

Please structure this as an early exit.

[Anastasia]

Restructure code with early return.

[rjmccall]

Thanks, LGTM.

[david-salinas]

This change has caused a regression for generic C++. Should this affect OpenCL only?

The following simple test causes the diagnostic to be emitted:

#define ATTR_GLOBAL attribute((address_space(1)))

int calc(int ATTR_GLOBAL *ip) {

int i = *ip;
return i+1;

}

int main() {

int i = 99;
int *ip = &i;

auto *g_i_ptr = reinterpret_cast<int  ATTR_GLOBAL*>(ip);
return calc(g_i_ptr);

}

[jhuber6]

Ran into this change trying to decay a qualifier pointer to a generic address space, e.g. https://godbolt.org/z/3dEd4TxjW. I understand that addrspace_cast was added to replace this functionality, but this isn't a C++ feature so as it stands there's no way to perform this operation in C++ and we need to rely on C-style casts to perform this basic functionality. I see it was brought up earlier, but should C++ really be limited by OpenCL here? I'm not aware of any specific mention of these, reinterpret_cast only explicitly disallows volatile and const qualifiers as far as I'm aware. The remaining case can be thought of as a compiler extension as [[clang::address_space(n)]] has no meaning otherwise.

See http://eel.is/c++draft/expr.reinterpret.cast#7 and the footnote.

[ebevhan]

In D58346#4359291, @jhuber6 wrote:

should C++ really be limited by OpenCL here?

It probably shouldn't. There's many places in the codebase where OpenCL flags restrict generic address space behavior. I have a patch at D62574 that attempts to formalize the address space rules a bit more (which I think also gets rid of the OpenCL restrictions you mention) but there's never been any huge interest and I don't have the time to push for it.

Whether that patch actually solves your problem or not, I don't know.

[jhuber6]

In D58346#4359631, @ebevhan wrote:

In D58346#4359291, @jhuber6 wrote:

should C++ really be limited by OpenCL here?

It probably shouldn't. There's many places in the codebase where OpenCL flags restrict generic address space behavior. I have a patch at D62574 that attempts to formalize the address space rules a bit more (which I think also gets rid of the OpenCL restrictions you mention) but there's never been any huge interest and I don't have the time to push for it.

Whether that patch actually solves your problem or not, I don't know.

A quick scan on where the error gets printed suggests not, since we'd also like the ability to add an address space. My suggestion is to allow reinterpret_cast to remove and and add address spaces for C++, OpenCL will remain the same.

include/clang/Basic/DiagnosticSemaKinds.td

def err_bad_cxx_cast_rvalue : Error<
   "%select{const_cast|static_cast|reinterpret_cast|dynamic_cast|C-style cast|"
   "functional-style cast}0 from rvalue to reference type %2">;
 def err_bad_cxx_cast_bitfield : Error<
   "%select{const_cast|static_cast|reinterpret_cast|dynamic_cast|C-style cast|"
   "functional-style cast}0 from bit-field lvalue to reference type %2">;
 def err_bad_cxx_cast_qualifiers_away : Error<
   "%select{const_cast|static_cast|reinterpret_cast|dynamic_cast|C-style cast|"
   "functional-style cast}0 from %1 to %2 casts away qualifiers">;
+def err_bad_cxx_cast_addr_space_mismatch : Error<
+  "%select{const_cast|static_cast|reinterpret_cast|dynamic_cast|C-style cast|"
+  "functional-style cast}0 from %1 to %2 converts between mismatching address"
+  " spaces">;
 def ext_bad_cxx_cast_qualifiers_away_incoherent : ExtWarn<
   "ISO C++ does not allow "
   "%select{const_cast|static_cast|reinterpret_cast|dynamic_cast|C-style cast|"
   "functional-style cast}0 from %1 to %2 because it casts away qualifiers, "
   "even though the source and destination types are unrelated">,
   SFINAEFailure, InGroup<DiagGroup<"cast-qual-unrelated">>;
 def err_bad_const_cast_dest : Error<
   "%select{const_cast||||C-style cast|functional-style cast}0 to %2, "

lib/Sema/SemaCast.cpp

static TryCastResult TryReinterpretCast(Sema &Self, ExprResult &SrcExpr,
   // C++ 5.2.10p2: The reinterpret_cast operator shall not cast away constness.
   // The C-style cast operator can.
   TryCastResult SuccessResult = TC_Success;
   if (auto CACK =
           CastsAwayConstness(Self, SrcType, DestType, /*CheckCVR=*/!CStyle,
                              /*CheckObjCLifetime=*/CStyle))
     SuccessResult = getCastAwayConstnessCastKind(CACK, msg);
 
-  if (IsLValueCast) {
+  if (IsAddressSpaceConversion(SrcType, DestType)) {
+    Kind = CK_AddressSpaceConversion;
+    assert(SrcType->isPointerType() && DestType->isPointerType());
+    if (!CStyle &&
+        !DestType->getPointeeType().getQualifiers().isAddressSpaceSupersetOf(
+            SrcType->getPointeeType().getQualifiers())) {
+      SuccessResult = TC_Failed;
+    }
+  } else if (IsLValueCast) {
     Kind = CK_LValueBitCast;
   } else if (DestType->isObjCObjectPointerType()) {
     Kind = Self.PrepareCastToObjCObjectPointer(SrcExpr);
   } else if (DestType->isBlockPointerType()) {
     if (!SrcType->isBlockPointerType()) {
       Kind = CK_AnyPointerToBlockPointerCast;
     } else {
       Kind = CK_BitCast;
     }
-  } else if (IsAddressSpaceConversion(SrcType, DestType)) {
-    Kind = CK_AddressSpaceConversion;
   } else {
     Kind = CK_BitCast;
   }
 
   // Any pointer can be cast to an Objective-C pointer type with a C-style
   // cast.
   if (CStyle && DestType->isObjCObjectPointerType()) {
     return SuccessResult;
static TryCastResult TryReinterpretCast(Sema &Self, ExprResult &SrcExpr,
   // C++ 5.2.10p7: A pointer to an object can be explicitly converted to
   //   a pointer to an object of different type.
   // Void pointers are not specified, but supported by every compiler out there.
   // So we finish by allowing everything that remains - it's got to be two
   // object pointers.
   return SuccessResult;
 }
 
+static TryCastResult TryAddressSpaceCast(Sema &Self, ExprResult &SrcExpr,
+                                         QualType DestType, bool CStyle,
+                                         unsigned &msg) {
+  if (Self.getLangOpts().OpenCL) {
+    auto SrcType = SrcExpr.get()->getType();
+    auto SrcPtrType = SrcType->getAs<PointerType>();
+    if (!SrcPtrType)
+      return TC_NotApplicable;
+    auto DestPtrType = DestType->getAs<PointerType>();
+    if (!DestPtrType)
+      return TC_NotApplicable;
+    auto SrcPointeeType = SrcPtrType->getPointeeType();
+    auto DestPointeeType = DestPtrType->getPointeeType();
+    if (SrcPointeeType.getAddressSpace() == DestPointeeType.getAddressSpace())
+      return TC_NotApplicable;
+    if (!DestPtrType->isAddressSpaceOverlapping(*SrcPtrType)) {
+      msg = diag::err_bad_cxx_cast_addr_space_mismatch;
+      return TC_Failed;
+    }
+    auto SrcPointeeTypeWithoutAS =
+        Self.Context.removeAddrSpaceQualType(SrcPointeeType.getCanonicalType());
+    auto DestPointeeTypeWithoutAS = Self.Context.removeAddrSpaceQualType(
+        DestPointeeType.getCanonicalType());
+    return Self.Context.hasSameType(SrcPointeeTypeWithoutAS,
+                                    DestPointeeTypeWithoutAS)
+               ? TC_Success
+               : TC_NotApplicable;
+  } else {
+    // FIXME: Need to define rules here
+    return TC_NotApplicable;
+  }
+}
+
 void CastOperation::checkAddressSpaceCast(QualType SrcType, QualType DestType) {
   // In OpenCL only conversions between pointers to objects in overlapping
   // addr spaces are allowed. v2.0 s6.5.5 - Generic addr space overlaps
   // with any named one, except for constant.
   if (Self.getLangOpts().OpenCL) {
     auto SrcPtrType = SrcType->getAs<PointerType>();
     if (!SrcPtrType)
       return;
void CastOperation::CheckCXXCStyleCast(bool FunctionalStyle,
   //   - a static_cast followed by a const_cast,
   //   - a reinterpret_cast, or
   //   - a reinterpret_cast followed by a const_cast,
   //   can be performed using the cast notation of explicit type conversion.
   //   [...] If a conversion can be interpreted in more than one of the ways
   //   listed above, the interpretation that appears first in the list is used,
   //   even if a cast resulting from that interpretation is ill-formed.
   // In plain language, this means trying a const_cast ...
+  // Note that for address space we check compatibility after const_cast.
   unsigned msg = diag::err_bad_cxx_cast_generic;
   TryCastResult tcr = TryConstCast(Self, SrcExpr, DestType,
                                    /*CStyle*/true, msg);
   if (SrcExpr.isInvalid())
     return;
   if (isValidCast(tcr))
     Kind = CK_NoOp;
 
   Sema::CheckedConversionKind CCK
     = FunctionalStyle? Sema::CCK_FunctionalCast
                      : Sema::CCK_CStyleCast;
   if (tcr == TC_NotApplicable) {
+    tcr = TryAddressSpaceCast(Self, SrcExpr, DestType, /*CStyle*/ true, msg);
+    if (SrcExpr.isInvalid())
+      return;
+    if (tcr == TC_NotApplicable) {
       // ... or if that is not possible, a static_cast, ignoring const, ...
-    tcr = TryStaticCast(Self, SrcExpr, DestType, CCK, OpRange,
-                        msg, Kind, BasePath, ListInitialization);
+      tcr = TryStaticCast(Self, SrcExpr, DestType, CCK, OpRange, msg, Kind,
+                          BasePath, ListInitialization);
       if (SrcExpr.isInvalid())
         return;
 
       if (tcr == TC_NotApplicable) {
         // ... and finally a reinterpret_cast, ignoring const.
-      tcr = TryReinterpretCast(Self, SrcExpr, DestType, /*CStyle*/true,
+        tcr = TryReinterpretCast(Self, SrcExpr, DestType, /*CStyle*/ true,
                                  OpRange, msg, Kind);
         if (SrcExpr.isInvalid())
           return;
       }
     }
+  }
 
   if (Self.getLangOpts().allowsNonTrivialObjCLifetimeQualifiers() &&
       isValidCast(tcr))
     checkObjCConversion(CCK);
 
   if (tcr != TC_Success && msg != 0) {
     if (SrcExpr.get()->getType() == Self.Context.OverloadTy) {
       DeclAccessPair Found;
if (SrcExpr.get()->getType() == Self.Context.OverloadTy) {
         Self.NoteAllOverloadCandidates(SrcExpr.get());
       }
     } else {
       diagnoseBadCast(Self, msg, (FunctionalStyle ? CT_Functional : CT_CStyle),
                       OpRange, SrcExpr.get(), DestType, ListInitialization);
     }
   }
 
-  checkAddressSpaceCast(SrcExpr.get()->getType(), DestType);
-
   if (isValidCast(tcr)) {
     if (Kind == CK_BitCast)
       checkCastAlign();
   } else {
     SrcExpr = ExprError();
   }
 }
 

test/SemaCXX/address-space-conversion.cpp

void test_dynamic_cast(A_ptr ap, A_ptr_1 ap1, A_ptr_2 ap2,
   (void)dynamic_cast<B_ptr_2>(ap); // expected-error{{casts away qualifiers}}
   (void)dynamic_cast<B_ptr_2>(ap1); // expected-error{{casts away qualifiers}}
 }
 
 void test_reinterpret_cast(void_ptr vp, void_ptr_1 vp1, void_ptr_2 vp2,
                            A_ptr ap, A_ptr_1 ap1, A_ptr_2 ap2,
                            B_ptr bp, B_ptr_1 bp1, B_ptr_2 bp2,
                            const void __attribute__((address_space(1))) *cvp1) {
-  // reinterpret_cast can be used to cast to a different address space.
-  (void)reinterpret_cast<A_ptr>(ap1);
-  (void)reinterpret_cast<A_ptr>(ap2);
+  // reinterpret_cast can't be used to cast to a different address space unless they are matching (i.e. overlapping).
+  (void)reinterpret_cast<A_ptr>(ap1); // expected-error{{reinterpret_cast from 'A_ptr_1' (aka '__attribute__((address_space(1))) A *') to 'A_ptr' (aka 'A *') is not allowed}}
+  (void)reinterpret_cast<A_ptr>(ap2); // expected-error{{reinterpret_cast from 'A_ptr_2' (aka '__attribute__((address_space(2))) A *') to 'A_ptr' (aka 'A *') is not allowed}}
   (void)reinterpret_cast<A_ptr>(bp);
-  (void)reinterpret_cast<A_ptr>(bp1);
-  (void)reinterpret_cast<A_ptr>(bp2);
+  (void)reinterpret_cast<A_ptr>(bp1); // expected-error{{reinterpret_cast from 'B_ptr_1' (aka '__attribute__((address_space(1))) B *') to 'A_ptr' (aka 'A *') is not allowed}}
+  (void)reinterpret_cast<A_ptr>(bp2); // expected-error{{reinterpret_cast from 'B_ptr_2' (aka '__attribute__((address_space(2))) B *') to 'A_ptr' (aka 'A *') is not allowed}}
   (void)reinterpret_cast<A_ptr>(vp);
-  (void)reinterpret_cast<A_ptr>(vp1);
-  (void)reinterpret_cast<A_ptr>(vp2);
-  (void)reinterpret_cast<A_ptr_1>(ap);
-  (void)reinterpret_cast<A_ptr_1>(ap2);
-  (void)reinterpret_cast<A_ptr_1>(bp);
+  (void)reinterpret_cast<A_ptr>(vp1); // expected-error{{reinterpret_cast from 'void_ptr_1' (aka '__attribute__((address_space(1))) void *') to 'A_ptr' (aka 'A *') is not allowed}}
+  (void)reinterpret_cast<A_ptr>(vp2); // expected-error{{reinterpret_cast from 'void_ptr_2' (aka '__attribute__((address_space(2))) void *') to 'A_ptr' (aka 'A *') is not allowed}}
+  (void)reinterpret_cast<A_ptr_1>(ap); // expected-error{{reinterpret_cast from 'A_ptr' (aka 'A *') to 'A_ptr_1' (aka '__attribute__((address_space(1))) A *') is not allowed}}
+  (void)reinterpret_cast<A_ptr_1>(ap2); // expected-error{{reinterpret_cast from 'A_ptr_2' (aka '__attribute__((address_space(2))) A *') to 'A_ptr_1' (aka '__attribute__((address_space(1))) A *') is not allowed}}
+  (void)reinterpret_cast<A_ptr_1>(bp); // expected-error{{reinterpret_cast from 'B_ptr' (aka 'B *') to 'A_ptr_1' (aka '__attribute__((address_space(1))) A *') is not allowed}}
   (void)reinterpret_cast<A_ptr_1>(bp1);
-  (void)reinterpret_cast<A_ptr_1>(bp2);
-  (void)reinterpret_cast<A_ptr_1>(vp);
+  (void)reinterpret_cast<A_ptr_1>(bp2); // expected-error{{reinterpret_cast from 'B_ptr_2' (aka '__attribute__((address_space(2))) B *') to 'A_ptr_1' (aka '__attribute__((address_space(1))) A *') is not allowed}}
+  (void)reinterpret_cast<A_ptr_1>(vp); // expected-error{{reinterpret_cast from 'void_ptr' (aka 'void *') to 'A_ptr_1' (aka '__attribute__((address_space(1))) A *') is not allowed}}
   (void)reinterpret_cast<A_ptr_1>(vp1);
-  (void)reinterpret_cast<A_ptr_1>(vp2);
+  (void)reinterpret_cast<A_ptr_1>(vp2); // expected-error{{reinterpret_cast from 'void_ptr_2' (aka '__attribute__((address_space(2))) void *') to 'A_ptr_1' (aka '__attribute__((address_space(1))) A *') is not allowed}}
 
   // ... but don't try to cast away constness!
   (void)reinterpret_cast<A_ptr_2>(cvp1); // expected-error{{casts away qualifiers}}
 }
 
 void test_cstyle_cast(void_ptr vp, void_ptr_1 vp1, void_ptr_2 vp2,
                       A_ptr ap, A_ptr_1 ap1, A_ptr_2 ap2,
                       B_ptr bp, B_ptr_1 bp1, B_ptr_2 bp2,

test/SemaOpenCL/address-spaces-conversions-cl2.0.cl

 // expected-error-re@-3{{initializing '__{{global|constant}} int *' with an expression of type '__generic int *' changes address space of pointer}}
 #else
 // expected-error-re@-5{{cannot initialize a variable of type '__{{global|constant}} int *' with an lvalue of type '__generic int *'}}
 #endif
 #endif
 
   AS int *var_cast1 = (AS int *)arg_glob;
 #ifdef CONSTANT
-// expected-error@-2{{casting '__global int *' to type '__constant int *' changes address space of pointer}}
+#if !__OPENCL_CPP_VERSION__
+// expected-error@-3{{casting '__global int *' to type '__constant int *' changes address space of pointer}}
+#else
+// expected-error@-5{{C-style cast from '__global int *' to '__constant int *' converts between mismatching address spaces}}
+#endif
 #endif
 
   AS int *var_cast2 = (AS int *)arg_loc;
 #ifndef GENERIC
-// expected-error-re@-2{{casting '__local int *' to type '__{{global|constant}} int *' changes address space of pointer}}
+#if !__OPENCL_CPP_VERSION__
+// expected-error-re@-3{{casting '__local int *' to type '__{{global|constant}} int *' changes address space of pointer}}
+#else
+// expected-error-re@-5{{C-style cast from '__local int *' to '__{{global|constant}} int *' converts between mismatching address spaces}}
+#endif
 #endif
 
   AS int *var_cast3 = (AS int *)arg_const;
 #ifndef CONSTANT
-// expected-error-re@-2{{casting '__constant int *' to type '__{{global|generic}} int *' changes address space of pointer}}
+#if !__OPENCL_CPP_VERSION__
+// expected-error-re@-3{{casting '__constant int *' to type '__{{global|generic}} int *' changes address space of pointer}}
+#else
+// expected-error-re@-5{{C-style cast from '__constant int *' to '__{{global|generic}} int *' converts between mismatching address spaces}}
+#endif
 #endif
 
   AS int *var_cast4 = (AS int *)arg_priv;
 #ifndef GENERIC
-// expected-error-re@-2{{casting 'int *' to type '__{{global|constant}} int *' changes address space of pointer}}
+#if !__OPENCL_CPP_VERSION__
+// expected-error-re@-3{{casting 'int *' to type '__{{global|constant}} int *' changes address space of pointer}}
+#else
+// expected-error-re@-5{{C-style cast from 'int *' to '__{{global|constant}} int *' converts between mismatching address spaces}}
+#endif
 #endif
 
   AS int *var_cast5 = (AS int *)arg_gen;
 #ifdef CONSTANT
-// expected-error@-2{{casting '__generic int *' to type '__constant int *' changes address space of pointer}}
+#if !__OPENCL_CPP_VERSION__
+// expected-error@-3{{casting '__generic int *' to type '__constant int *' changes address space of pointer}}
+#else
+// expected-error@-5{{C-style cast from '__generic int *' to '__constant int *' converts between mismatching address spaces}}
+#endif
 #endif
 
   AS int *var_impl;
   var_impl = arg_glob;
 #ifdef CONSTANT
 #if !__OPENCL_CPP_VERSION__
 // expected-error@-3{{assigning '__global int *' to '__constant int *' changes address space of pointer}}
 #else

 // expected-error-re@-3{{assigning '__generic int *' to '__{{global|constant}} int *' changes address space of pointer}}
 #else
 // expected-error-re@-5{{assigning to '__{{global|constant}} int *' from incompatible type '__generic int *'}}
 #endif
 #endif
 
   var_cast1 = (AS int *)arg_glob;
 #ifdef CONSTANT
-// expected-error@-2{{casting '__global int *' to type '__constant int *' changes address space of pointer}}
+#if !__OPENCL_CPP_VERSION__
+// expected-error@-3{{casting '__global int *' to type '__constant int *' changes address space of pointer}}
+#else
+// expected-error@-5{{C-style cast from '__global int *' to '__constant int *' converts between mismatching address spaces}}
+#endif
 #endif
 
   var_cast2 = (AS int *)arg_loc;
 #ifndef GENERIC
-// expected-error-re@-2{{casting '__local int *' to type '__{{global|constant}} int *' changes address space of pointer}}
+#if !__OPENCL_CPP_VERSION__
+// expected-error-re@-3{{casting '__local int *' to type '__{{global|constant}} int *' changes address space of pointer}}
+#else
+// expected-error-re@-5{{C-style cast from '__local int *' to '__{{global|constant}} int *' converts between mismatching address spaces}}
+#endif
 #endif
 
   var_cast3 = (AS int *)arg_const;
 #ifndef CONSTANT
-// expected-error-re@-2{{casting '__constant int *' to type '__{{global|generic}} int *' changes address space of pointer}}
+#if !__OPENCL_CPP_VERSION__
+// expected-error-re@-3{{casting '__constant int *' to type '__{{global|generic}} int *' changes address space of pointer}}
+#else
+// expected-error-re@-5{{C-style cast from '__constant int *' to '__{{global|generic}} int *' converts between mismatching address spaces}}
+#endif
 #endif
 
   var_cast4 = (AS int *)arg_priv;
 #ifndef GENERIC
-// expected-error-re@-2{{casting 'int *' to type '__{{global|constant}} int *' changes address space of pointer}}
+#if !__OPENCL_CPP_VERSION__
+// expected-error-re@-3{{casting 'int *' to type '__{{global|constant}} int *' changes address space of pointer}}
+#else
+// expected-error-re@-5{{C-style cast from 'int *' to '__{{global|constant}} int *' converts between mismatching address spaces}}
+#endif
 #endif
 
   var_cast5 = (AS int *)arg_gen;
 #ifdef CONSTANT
-// expected-error@-2{{casting '__generic int *' to type '__constant int *' changes address space of pointer}}
+#if !__OPENCL_CPP_VERSION__
+// expected-error@-3{{casting '__generic int *' to type '__constant int *' changes address space of pointer}}
+#else
+// expected-error@-5{{C-style cast from '__generic int *' to '__constant int *' converts between mismatching address spaces}}
+#endif
 #endif
 
   AS int *var_cmp;
   int b = var_cmp != arg_glob;
 #ifdef CONSTANT
 #if !__OPENCL_CPP_VERSION__
 // expected-error@-3{{comparison between  ('__constant int *' and '__global int *') which are pointers to non-overlapping address spaces}}
 #else

test/SemaOpenCL/address-spaces.cl

 // expected-error@-2 {{assigning '__constant int *' to '__generic int *' changes address space of pointer}}
 #else
 // expected-error@-4 {{assigning to '__generic int *' from incompatible type '__constant int *'}}
 #endif
 #endif
 }
 
 void explicit_cast(__global int *g, __local int *l, __constant int *c, __private int *p, const __constant int *cc) {
-  g = (__global int *)l;  // expected-error {{casting '__local int *' to type '__global int *' changes address space of pointer}}
-  g = (__global int *)c;  // expected-error {{casting '__constant int *' to type '__global int *' changes address space of pointer}}
-  g = (__global int *)cc; // expected-error {{casting 'const __constant int *' to type '__global int *' changes address space of pointer}}
-  g = (__global int *)p;  // expected-error {{casting 'int *' to type '__global int *' changes address space of pointer}}
-
-  l = (__local int *)g;  // expected-error {{casting '__global int *' to type '__local int *' changes address space of pointer}}
-  l = (__local int *)c;  // expected-error {{casting '__constant int *' to type '__local int *' changes address space of pointer}}
-  l = (__local int *)cc; // expected-error {{casting 'const __constant int *' to type '__local int *' changes address space of pointer}}
-  l = (__local int *)p;  // expected-error {{casting 'int *' to type '__local int *' changes address space of pointer}}
-
-  c = (__constant int *)g; // expected-error {{casting '__global int *' to type '__constant int *' changes address space of pointer}}
-  c = (__constant int *)l; // expected-error {{casting '__local int *' to type '__constant int *' changes address space of pointer}}
-  c = (__constant int *)p; // expected-error {{casting 'int *' to type '__constant int *' changes address space of pointer}}
-
-  p = (__private int *)g;  // expected-error {{casting '__global int *' to type 'int *' changes address space of pointer}}
-  p = (__private int *)l;  // expected-error {{casting '__local int *' to type 'int *' changes address space of pointer}}
-  p = (__private int *)c;  // expected-error {{casting '__constant int *' to type 'int *' changes address space of pointer}}
-  p = (__private int *)cc; // expected-error {{casting 'const __constant int *' to type 'int *' changes address space of pointer}}
+  g = (__global int *)l;
+#if !__OPENCL_CPP_VERSION__
+// expected-error@-2 {{casting '__local int *' to type '__global int *' changes address space of pointer}}
+#else
+// expected-error@-4 {{C-style cast from '__local int *' to '__global int *' converts between mismatching address spaces}}
+#endif
+  g = (__global int *)c;
+#if !__OPENCL_CPP_VERSION__
+// expected-error@-2 {{casting '__constant int *' to type '__global int *' changes address space of pointer}}
+#else
+// expected-error@-4 {{C-style cast from '__constant int *' to '__global int *' converts between mismatching address spaces}}
+#endif
+  g = (__global int *)cc;
+#if !__OPENCL_CPP_VERSION__
+// expected-error@-2 {{casting 'const __constant int *' to type '__global int *' changes address space of pointer}}
+#else
+// expected-error@-4 {{C-style cast from 'const __constant int *' to '__global int *' converts between mismatching address spaces}}
+#endif
+  g = (__global int *)p;
+#if !__OPENCL_CPP_VERSION__
+// expected-error@-2 {{casting 'int *' to type '__global int *' changes address space of pointer}}
+#else
+// expected-error@-4 {{C-style cast from 'int *' to '__global int *' converts between mismatching address spaces}}
+#endif
+  l = (__local int *)g;
+#if !__OPENCL_CPP_VERSION__
+// expected-error@-2 {{casting '__global int *' to type '__local int *' changes address space of pointer}}
+#else
+// expected-error@-4 {{C-style cast from '__global int *' to '__local int *' converts between mismatching address spaces}}
+#endif
+  l = (__local int *)c;
+#if !__OPENCL_CPP_VERSION__
+// expected-error@-2 {{casting '__constant int *' to type '__local int *' changes address space of pointer}}
+#else
+// expected-error@-4 {{C-style cast from '__constant int *' to '__local int *' converts between mismatching address spaces}}
+#endif
+  l = (__local int *)cc;
+#if !__OPENCL_CPP_VERSION__
+// expected-error@-2 {{casting 'const __constant int *' to type '__local int *' changes address space of pointer}}
+#else
+// expected-error@-4 {{C-style cast from 'const __constant int *' to '__local int *' converts between mismatching address spaces}}
+#endif
+  l = (__local int *)p;
+#if !__OPENCL_CPP_VERSION__
+// expected-error@-2 {{casting 'int *' to type '__local int *' changes address space of pointer}}
+#else
+// expected-error@-4 {{C-style cast from 'int *' to '__local int *' converts between mismatching address spaces}}
+#endif
+  c = (__constant int *)g;
+#if !__OPENCL_CPP_VERSION__
+// expected-error@-2 {{casting '__global int *' to type '__constant int *' changes address space of pointer}}
+#else
+// expected-error@-4 {{C-style cast from '__global int *' to '__constant int *' converts between mismatching address spaces}}
+#endif
+  c = (__constant int *)l;
+#if !__OPENCL_CPP_VERSION__
+// expected-error@-2 {{casting '__local int *' to type '__constant int *' changes address space of pointer}}
+#else
+// expected-error@-4 {{C-style cast from '__local int *' to '__constant int *' converts between mismatching address spaces}}
+#endif
+  c = (__constant int *)p;
+#if !__OPENCL_CPP_VERSION__
+// expected-error@-2 {{casting 'int *' to type '__constant int *' changes address space of pointer}}
+#else
+// expected-error@-4 {{C-style cast from 'int *' to '__constant int *' converts between mismatching address spaces}}
+#endif
+  p = (__private int *)g;
+#if !__OPENCL_CPP_VERSION__
+// expected-error@-2 {{casting '__global int *' to type 'int *' changes address space of pointer}}
+#else
+// expected-error@-4 {{C-style cast from '__global int *' to 'int *' converts between mismatching address spaces}}
+#endif
+  p = (__private int *)l;
+#if !__OPENCL_CPP_VERSION__
+// expected-error@-2 {{casting '__local int *' to type 'int *' changes address space of pointer}}
+#else
+// expected-error@-4 {{C-style cast from '__local int *' to 'int *' converts between mismatching address spaces}}
+#endif
+  p = (__private int *)c;
+#if !__OPENCL_CPP_VERSION__
+// expected-error@-2 {{casting '__constant int *' to type 'int *' changes address space of pointer}}
+#else
+// expected-error@-4 {{C-style cast from '__constant int *' to 'int *' converts between mismatching address spaces}}
+#endif
+  p = (__private int *)cc;
+#if !__OPENCL_CPP_VERSION__
+// expected-error@-2 {{casting 'const __constant int *' to type 'int *' changes address space of pointer}}
+#else
+// expected-error@-4 {{C-style cast from 'const __constant int *' to 'int *' converts between mismatching address spaces}}
+#endif
 }
 
 void ok_explicit_casts(__global int *g, __global int *g2, __local int *l, __local int *l2, __private int *p, __private int *p2) {
   g = (__global int *)g2;
   l = (__local int *)l2;
   p = (__private int *)p2;
 }