r299080 - [ARC][ObjC++] Use ObjC semantic rules for comparisons between a pointer and

[Alex Lorenz via cfe-commits]

Author: arphaman
Date: Thu Mar 30 08:48:33 2017
New Revision: 299080

URL: http://llvm.org/viewvc/llvm-project?rev=299080&view=rev
Log:
[ARC][ObjC++] Use ObjC semantic rules for comparisons between a pointer and
an ObjC object pointer

When ARC is enabled in Objective-C++, comparisons between a pointer and
Objective-C object pointer typically result in errors like this:
"invalid operands to a binary expression". This error message can be quite
confusing as it doesn't provide a solution to the problem, unlike the non-C++
diagnostic: "implicit conversion of Objective-C pointer type 'id' to C pointer
type 'void *' requires a bridged cast" (it also provides fix-its). This commit
forces comparisons between pointers and Objective-C object pointers in ARC to
use the Objective-C semantic rules to ensure that a better diagnostic is
reported.

rdar://31103857

Differential Revision: https://reviews.llvm.org/D31177

Added:
    cfe/trunk/test/SemaObjCXX/arc-ptr-comparison.mm
Modified:
    cfe/trunk/lib/Sema/SemaExpr.cpp

Modified: cfe/trunk/lib/Sema/SemaExpr.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaExpr.cpp?rev=299080&r1=299079&r2=299080&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaExpr.cpp (original)
+++ cfe/trunk/lib/Sema/SemaExpr.cpp Thu Mar 30 08:48:33 2017
@@ -9423,7 +9423,10 @@ QualType Sema::CheckCompareOperands(Expr
     //   If both operands are pointers, [...] bring them to their composite
     //   pointer type.
     if ((int)LHSType->isPointerType() + (int)RHSType->isPointerType() >=
-        (IsRelational ? 2 : 1)) {
+            (IsRelational ? 2 : 1) &&
+        (!LangOpts.ObjCAutoRefCount ||
+         !(LHSType->isObjCObjectPointerType() ||
+           RHSType->isObjCObjectPointerType()))) {
       if (convertPointersToCompositeType(*this, Loc, LHS, RHS))
         return QualType();
       else

Added: cfe/trunk/test/SemaObjCXX/arc-ptr-comparison.mm
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaObjCXX/arc-ptr-comparison.mm?rev=299080&view=auto
==============================================================================
--- cfe/trunk/test/SemaObjCXX/arc-ptr-comparison.mm (added)
+++ cfe/trunk/test/SemaObjCXX/arc-ptr-comparison.mm Thu Mar 30 08:48:33 2017
@@ -0,0 +1,24 @@
+// RUN: %clang_cc1 -std=c++11 -triple x86_64-apple-darwin11 -fsyntax-only -fobjc-arc -verify %s
+// RUN: %clang_cc1 -std=c++11 -triple x86_64-apple-darwin11 -fsyntax-only -verify -DNOARC %s
+#ifdef NOARC
+// expected-no-diagnostics
+#endif
+
+int testObjCComparisonRules(void *v, id x, id y) {
+  return v == x;
+#ifndef NOARC
+// expected-error at -2 {{implicit conversion of Objective-C pointer type 'id' to C pointer type 'void *' requires a bridged cast}}
+// expected-note at -3 {{use __bridge to convert directly (no change in ownership)}}
+// expected-note at -4 {{use __bridge_retained to make an ARC object available as a +1 'void *'}}
+#endif
+  return v >= x;
+#ifndef NOARC
+// expected-error at -2 {{implicit conversion of Objective-C pointer type 'id' to C pointer type 'void *' requires a bridged cast}}
+// expected-note at -3 {{use __bridge to convert directly (no change in ownership)}}
+// expected-note at -4 {{use __bridge_retained to make an ARC object available as a +1 'void *'}}
+#endif
+  return v == (id)(void *)0; // OK
+  return v == nullptr; // OK
+  return v == (void *)0;
+  return x == y;
+}