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

[Fariborz Jahanian]

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;
}


int main() (CompoundStmt 0x103815ab0 <p.m:6:1, line:9:1>
   (DeclStmt 0x103816e90 <line:7:3, col:7>
     0x103816e40 "B *b"
   (BinaryOperator 0x103816f60 <line:8:3, col:14> 'int' '='
     (ObjCPropertyRefExpr 0x103816ee0 <col:3, col:5> 'int'  
Kind=PropertyRef Property="MyProp"
       (DeclRefExpr 0x103816eb0 <col:3> 'B *' Var='b' 0x103816e40))
     (IntegerLiteral 0x103816f20 <col:14> 'int' 100)))

- Fariborz

>
> 	- Doug
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