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

[Ted Kremenek]

OtherExpr is being used in the branch at the end.

On Apr 22, 2013, at 4:31 PM, Jordan Rose <jordan_rose at apple.com> wrote:

> It looks like OtherExpr is unused now; should it be removed?
> 
> 
> On Apr 22, 2013, at 15:46 , 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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>