Warn when property ivar lookup finds a global variable

of same name. In nonfragile-abi2, lookup accesses a synthesized
ivar. This is a transition warning.  Radar 8225011.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@109197 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 49 insertions, 2 deletions

diff --git a/include/clang/Basic/DiagnosticGroups.td b/include/clang/Basic/DiagnosticGroups.td
index 033b6c4214..f0c556ce3a 100644
--- a/include/clang/Basic/DiagnosticGroups.td
+++ b/include/clang/Basic/DiagnosticGroups.td
@@ -135,6 +135,7 @@ def ReadOnlySetterAttrs : DiagGroup<"readonly-setter-attrs">;
 def Reorder : DiagGroup<"reorder">;
 def UndeclaredSelector : DiagGroup<"undeclared-selector">;
 def Selector : DiagGroup<"selector">;
+def NonfragileAbi2 : DiagGroup<"nonfragile-abi2">;
 def Protocol : DiagGroup<"protocol">;
 def SuperSubClassMismatch : DiagGroup<"super-class-method-mismatch">;
 def : DiagGroup<"variadic-macros">;
diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index 6fb53189cd..12933ca601 100644
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@@ -2492,6 +2492,10 @@ def note_condition_assign_silence : Note<
 def warn_value_always_zero : Warning<
   "%0 is always %select{zero|false|NULL}1 in this context">;
 
+def warn_ivar_variable_conflict : Warning<
+  "%0 lookup will access the property ivar in nonfragile-abi2 mode">, 
+  InGroup<NonfragileAbi2>;
+
 // assignment related diagnostics (also for argument passing, returning, etc).
 // In most of these diagnostics the %2 is a value from the
 // Sema::AssignmentAction enumeration
diff --git a/lib/Sema/SemaExpr.cpp b/lib/Sema/SemaExpr.cpp
index 58bc4f0801..d2f68e0331 100644
--- a/lib/Sema/SemaExpr.cpp
+++ b/lib/Sema/SemaExpr.cpp
@@ -1005,6 +1005,25 @@ bool Sema::DiagnoseEmptyLookup(Scope *S, CXXScopeSpec &SS, LookupResult &R,
   return true;
 }
 
+static ObjCPropertyDecl *OkToSynthesizeProvisionalIvar(Sema &SemaRef,
+                                          IdentifierInfo *II,
+                                          SourceLocation NameLoc) {
+  ObjCMethodDecl *CurMeth = SemaRef.getCurMethodDecl();
+  ObjCInterfaceDecl *IDecl = CurMeth->getClassInterface();
+  if (!IDecl)
+    return 0;
+  ObjCImplementationDecl *ClassImpDecl = IDecl->getImplementation();
+  if (!ClassImpDecl)
+    return 0;
+  ObjCPropertyDecl *property = SemaRef.LookupPropertyDecl(IDecl, II);
+  if (!property)
+    return 0;
+  if (ObjCPropertyImplDecl *PIDecl = ClassImpDecl->FindPropertyImplDecl(II))
+    if (PIDecl->getPropertyImplementation() == ObjCPropertyImplDecl::Dynamic)
+      return 0;
+  return property;
+}
+
 static ObjCIvarDecl *SynthesizeProvisionalIvar(Sema &SemaRef,
                                                IdentifierInfo *II,
                                                SourceLocation NameLoc) {
@@ -1077,7 +1096,7 @@ Sema::OwningExprResult Sema::ActOnIdExpression(Scope *S,
                                       isAddressOfOperand,
                                       TemplateArgs);
   }
-
+  bool IvarLookupFollowUp = false;
   // Perform the required lookup.
   LookupResult R(*this, Name, NameLoc, LookupOrdinaryName);
   if (TemplateArgs) {
@@ -1090,7 +1109,7 @@ Sema::OwningExprResult Sema::ActOnIdExpression(Scope *S,
     LookupTemplateName(R, S, SS, QualType(), /*EnteringContext=*/false,
                        MemberOfUnknownSpecialization);
   } else {
-    bool IvarLookupFollowUp = (!SS.isSet() && II && getCurMethodDecl());
+    IvarLookupFollowUp = (!SS.isSet() && II && getCurMethodDecl());
     LookupParsedName(R, S, &SS, !IvarLookupFollowUp);
 
     // If this reference is in an Objective-C method, then we need to do
@@ -1151,6 +1170,16 @@ Sema::OwningExprResult Sema::ActOnIdExpression(Scope *S,
   assert(!R.empty() || ADL);
 
   if (VarDecl *Var = R.getAsSingle<VarDecl>()) {
+    if (getLangOptions().ObjCNonFragileABI && IvarLookupFollowUp &&
+        !getLangOptions().ObjCNonFragileABI2) {
+      ObjCPropertyDecl *Property = 
+        OkToSynthesizeProvisionalIvar(*this, II, NameLoc);
+      if (Property) {
+        Diag(NameLoc, diag::warn_ivar_variable_conflict) << Var->getDeclName();
+        Diag(Property->getLocation(), diag::note_property_declare);
+      }
+    }
+    
     // Warn about constructs like:
     //   if (void *X = foo()) { ... } else { X }.
     // In the else block, the pointer is always false.
diff --git a/test/SemaObjC/conflict-nonfragile-abi2.m b/test/SemaObjC/conflict-nonfragile-abi2.m
new file mode 100644
index 0000000000..49cff97ccb
--- /dev/null
+++ b/test/SemaObjC/conflict-nonfragile-abi2.m
@@ -0,0 +1,13 @@
+// RUN: %clang_cc1 -fobjc-nonfragile-abi -verify -fsyntax-only %s
+// rdar : // 8225011
+
+int glob;
+
+@interface I
+@property int glob; // expected-note {{property declared here}}
+@end
+
+@implementation I
+- (int) Meth { return glob; } // expected-warning {{'glob' lookup will access the property ivar in nonfragile-abi2 mode}}
+@synthesize glob;
+@end