[cfe-commits] r94826 - in /cfe/trunk: lib/AST/Expr.cpp lib/Sema/SemaInit.cpp lib/Sema/SemaInit.h test/CodeGenCXX/reference-init.cpp

[Douglas Gregor]

Sent from my iPhone

On Jan 30, 2010, at 11:11 AM, Fariborz Jahanian <fjahanian at apple.com>  
wrote:

>
> On Jan 29, 2010, at 2:58 PM, Douglas Gregor wrote:
>
>>
>> On Jan 29, 2010, at 2:53 PM, Eli Friedman wrote:
>>
>>> On Fri, Jan 29, 2010 at 2:05 PM, Douglas Gregor  
>>> <dgregor at apple.com> wrote:
>>>>
>>>> On Jan 29, 2010, at 1:36 PM, Eli Friedman wrote:
>>>>
>>>>> On Fri, Jan 29, 2010 at 1:12 PM, Chris Lattner  
>>>>> <clattner at apple.com> wrote:
>>>>>>
>>>>>> On Jan 29, 2010, at 11:14 AM, Douglas Gregor wrote:
>>>>>>
>>>>>>> Author: dgregor
>>>>>>> Date: Fri Jan 29 13:14:02 2010
>>>>>>> New Revision: 94826
>>>>>>>
>>>>>>> URL: http://llvm.org/viewvc/llvm-project?rev=94826&view=rev
>>>>>>> Log:
>>>>>>> Fix reference binding of const lvalue references to bit- 
>>>>>>> fields, which
>>>>>>> requires a temporary. Previously, we were building an  
>>>>>>> initialization
>>>>>>> sequence that bound to the bit-field as if it were a real  
>>>>>>> lvalue. Note
>>>>>>> that we previously (and still) diagnose binding of non-const
>>>>>>> references to bit-fields, as we should.
>>>>>>
>>>>>> Does this also work for opencl vector elements?  Something like  
>>>>>> this:
>>>>>>
>>>>>>
>>>>>> float &x = myfloat4.x;
>>>>>>
>>>>>> should be invalid, but:
>>>>>> float x = myfloat4.x;
>>>>>>
>>>>>> is ok.  Very similar to bitfields,
>>>>>
>>>>> We don't check for it at all... we silently build a temporary  
>>>>> for the following:
>>>>> typedef int V __attribute((ext_vector_type(4)));
>>>>> V x;
>>>>> void a() { int& y = x[0]; }
>>>>
>>>> BUG! I'll take a look when I can. Thanks Chris, Eli.
>>>>
>>>>> I don't know enough ObjC to make a testcase, but I think the same
>>>>> issue affects ObjC properties.
>>>>
>>>>
>>>> It shouldn't, because an ObjCPropertyRefExpr is not an lvalue.  
>>>> However, I'll still test it :)
>>>>
>>>>      - Doug
>>>
>>> Umm, from Expr::isLvalueInternal:
>>>
>>> case ObjCPropertyRefExprClass: // FIXME: check if read-only  
>>> property.
>>>  return LV_Valid;
>>
>>
>> Oh, weird. I was looking at the other places where we check for  
>> ObjCPropertyRefExpr.... looks like I'll need to dig into this one  
>> further.
>
> It is an lvalue; similary in many aspects to MemRefExpr:
>
> [jahan8:~] fjahania% cat p.m
> @interface B
> @property int MyProp;
> @end
>
> int main()
> {
>  B *b;
>  b.MyProp = 100;
> }

Sure, but it's an lvalue without an underlying object, so this should  
be I'll-formed:

   int & ir = b.MyProp;

While this needs to call the getter and bind to the resulting temporary:

   const int & ir = b.MyProp;

   - Doug
>