Add a warning for Objective-C pointer introspection, which is solely the job of the Objective-C runtime.

llvm-svn: 180062

Author: tkremenek

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -642,6 +642,10 @@ def warn_objc_isa_use : Warning<
 def warn_objc_isa_assign : Warning<
   "assignment to Objective-C's isa is deprecated in favor of "
   "object_setClass()">, InGroup<DeprecatedObjCIsaUsage>;
+def warn_objc_pointer_masking : Warning<
+  "bitmasking for introspection of Objective-C object pointers is strongly "
+  "discouraged in favor of using runtime APIs">,
+  InGroup<DiagGroup<"deprecated-objc-pointer-introspection">>;
 def warn_objc_property_default_assign_on_object : Warning<
   "default property attribute 'assign' not appropriate for non-GC object">,
   InGroup<ObjCPropertyNoAttribute>;

clang/lib/Sema/SemaExpr.cpp

@@ -8559,6 +8559,36 @@ static void DiagnoseSelfAssignment(Sema &S, Expr *LHSExpr, Expr *RHSExpr,
       << LHSExpr->getSourceRange() << RHSExpr->getSourceRange();
 }
 
+/// Check if a bitwise-& is performed on an Objective-C pointer.  This
+/// is usually indicative of introspection within the Objective-C pointer.
+static void checkObjCPointerIntrospection(Sema &S, ExprResult &L, ExprResult &R,
+                                          SourceLocation OpLoc) {
+  if (!S.getLangOpts().ObjC1)
+    return;
+
+  const Expr *ObjCPointerExpr = 0, *OtherExpr = 0;
+  const Expr *LHS = L.get();
+  const Expr *RHS = R.get();
+
+  if (LHS->IgnoreParenCasts()->getType()->isObjCObjectPointerType()) {
+    ObjCPointerExpr = LHS;
+    OtherExpr = RHS;
+  }
+  else if (RHS->IgnoreParenCasts()->getType()->isObjCObjectPointerType()) {
+    ObjCPointerExpr = RHS;
+    OtherExpr = LHS;
+  }
+
+  // This warning is deliberately made very specific to reduce false
+  // positives with logic that uses '&' for hashing.  This logic mainly
+  // looks for code trying to introspect into tagged pointers, which
+  // code should generally never do.
+  if (ObjCPointerExpr && isa<IntegerLiteral>(OtherExpr->IgnoreParenCasts())) {
+    S.Diag(OpLoc, diag::warn_objc_pointer_masking)
+      << ObjCPointerExpr->getSourceRange();
+  }
+}
+
 /// CreateBuiltinBinOp - Creates a new built-in binary operation with
 /// operator @p Opc at location @c TokLoc. This routine only supports
 /// built-in operations; ActOnBinOp handles overloaded operators.
@@ -8636,6 +8666,7 @@ ExprResult Sema::CreateBuiltinBinOp(SourceLocation OpLoc,
     ResultTy = CheckCompareOperands(LHS, RHS, OpLoc, Opc, false);
     break;
   case BO_And:
+    checkObjCPointerIntrospection(*this, LHS, RHS, OpLoc);
   case BO_Xor:
   case BO_Or:
     ResultTy = CheckBitwiseOperands(LHS, RHS, OpLoc);