-Warc-repeated-use-of-weak: check ivars and variables as well.

Like properties, loading from a weak ivar twice in the same function can
give you inconsistent results if the object is deallocated between the
two loads. It is safer to assign to a strong local variable and use that.

Second half of <rdar://problem/12280249>.

llvm-svn: 164855

1 files changed, 25 insertions, 3 deletions

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 597e4d6f77c..0570dd38c79 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -1425,6 +1425,15 @@ Sema::BuildDeclRefExpr(ValueDecl *D, QualType Ty, ExprValueKind VK,
 
   MarkDeclRefReferenced(E);
 
+  if (getLangOpts().ObjCARCWeak && isa<VarDecl>(D) &&
+      Ty.getObjCLifetime() == Qualifiers::OCL_Weak) {
+    DiagnosticsEngine::Level Level =
+      Diags.getDiagnosticLevel(diag::warn_arc_repeated_use_of_weak,
+                               E->getLocStart());
+    if (Level != DiagnosticsEngine::Ignored)
+      getCurFunction()->recordUseOfWeak(E);
+  }
+
   // Just in case we're building an illegal pointer-to-member.
   FieldDecl *FD = dyn_cast<FieldDecl>(D);
   if (FD && FD->isBitField())
@@ -1986,9 +1995,22 @@ Sema::LookupInObjCMethod(LookupResult &Lookup, Scope *S,
       ObjCMethodFamily MF = CurMethod->getMethodFamily();
       if (MF != OMF_init && MF != OMF_dealloc && MF != OMF_finalize)
         Diag(Loc, diag::warn_direct_ivar_access) << IV->getDeclName();
-      return Owned(new (Context)
-                   ObjCIvarRefExpr(IV, IV->getType(), Loc,
-                                   SelfExpr.take(), true, true));
+
+      ObjCIvarRefExpr *Result = new (Context) ObjCIvarRefExpr(IV, IV->getType(),
+                                                              Loc,
+                                                              SelfExpr.take(),
+                                                              true, true);
+
+      if (getLangOpts().ObjCAutoRefCount) {
+        if (IV->getType().getObjCLifetime() == Qualifiers::OCL_Weak) {
+          DiagnosticsEngine::Level Level =
+            Diags.getDiagnosticLevel(diag::warn_arc_repeated_use_of_weak, Loc);
+          if (Level != DiagnosticsEngine::Ignored)
+            getCurFunction()->recordUseOfWeak(Result);
+        }
+      }
+      
+      return Owned(Result);
     }
   } else if (CurMethod->isInstanceMethod()) {
     // We should warn if a local variable hides an ivar.