r180062 - Add a warning for Objective-C pointer introspection, which is solely the job of the Objective-C runtime.

[jahanian]

Couple of points. Test case is missing. Can we suggest what those APIs are and provide fixit’s if it is not
too complicated to do?

- Fariborz

On Apr 22, 2013, at 3:46 PM, Ted Kremenek <kremenek at apple.com> wrote:

> Author: kremenek
> Date: Mon Apr 22 17:46:52 2013
> New Revision: 180062
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=180062&view=rev
> Log:
> Add a warning for Objective-C pointer introspection, which is solely the job of the Objective-C runtime.
> 
> Modified:
>    cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
>    cfe/trunk/lib/Sema/SemaExpr.cpp
> 
> Modified: cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td?rev=180062&r1=180061&r2=180062&view=diff
> ==============================================================================
> --- cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td (original)
> +++ cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td Mon Apr 22 17:46:52 2013
> @@ -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>;
> 
> Modified: cfe/trunk/lib/Sema/SemaExpr.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaExpr.cpp?rev=180062&r1=180061&r2=180062&view=diff
> ==============================================================================
> --- cfe/trunk/lib/Sema/SemaExpr.cpp (original)
> +++ cfe/trunk/lib/Sema/SemaExpr.cpp Mon Apr 22 17:46:52 2013
> @@ -8559,6 +8559,36 @@ static void DiagnoseSelfAssignment(Sema
>       << 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(Sour
>     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);
> 
> 
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