address of overloaded function with no contextual type information

address of overloaded function with no contextual type information

[Adam Burr]

Does anyone know what I'm doing wrong here?


#include <iostream>

template< typename T >
struct thingA
{
    template< int I >
    static int doA () {return I;}

    struct thingB
    {
        void doB ()
        {
            // this line does not compile:
            int (*doAPtr) () = &thingA< T >::doA< 2 >;
            std::cerr << (*doAPtr) () << std::endl;
        }
    };
};

int main (int, char **)
{
    thingA< int >::thingB a;
    a.doB ();
}


This is a contrived example but in the "real world" I do need to get a 
pointer to a static template function inside a template class like this.


Here is the gcc error:

main.cc: In member function 'void thingA<T>::thingB::doB()':
main.cc:14: error: expected primary-expression before ';' token
main.cc: In member function 'void thingA<T>::thingB::doB() [with T = int]':
main.cc:23:   instantiated from here
main.cc:14: error: address of overloaded function with no contextual 
type information


Any help is appreciated.

Thanks,
Adam Burr
Blue Sky Studios

Re: address of overloaded function with no contextual type information

[Tiago Maluta]

Hi Adam,

Change the line:
>           int (*doAPtr) () = &thingA< T >::doA< 2 >;

To:
int (*doAPtr)() = &thingA< int >::doA< 2 >;

--tm

Re: address of overloaded function with no contextual type information

[Adam Burr]

Tiago Maluta wrote:
> Hi Adam,
>
> Change the line:
>   
>>           int (*doAPtr) () = &thingA< T >::doA< 2 >;
>>     
>
> To:
> int (*doAPtr)() = &thingA< int >::doA< 2 >;
>
> --tm
>   
Yes, that works but it isn't what I need. Luckily I just figured it out! 
That line should be:

int (*doAPtr) () = &thingA< T >::template doA< 2 >;

Re: address of overloaded function with no contextual type information

[Tiago Maluta]

On Wed, Aug 11, 2010 at 9:50 PM, Adam Burr <adamb@blueskystudios.com> wrote:
> Tiago Maluta wrote:
>>
>> Hi Adam,
>>
>> Change the line:
>>
>>>
>>>          int (*doAPtr) () = &thingA< T >::doA< 2 >;
>>>
>>
>> To:
>> int (*doAPtr)() = &thingA< int >::doA< 2 >;
>>
>
> Yes, that works but it isn't what I need. Luckily I just figured it out!
> That line should be:
>
> int (*doAPtr) () = &thingA< T >::template doA< 2 >;
>
>

I dind't know that construction, thanks.

--tm

Re: address of overloaded function with no contextual type information

[Adam Burr]

Tiago Maluta wrote:
> On Wed, Aug 11, 2010 at 9:50 PM, Adam Burr <adamb@blueskystudios.com> wrote:
>   
>> Tiago Maluta wrote:
>>     
>>> Hi Adam,
>>>
>>> Change the line:
>>>
>>>       
>>>>          int (*doAPtr) () = &thingA< T >::doA< 2 >;
>>>>
>>>>         
>>> To:
>>> int (*doAPtr)() = &thingA< int >::doA< 2 >;
>>>
>>>       
>> Yes, that works but it isn't what I need. Luckily I just figured it out!
>> That line should be:
>>
>> int (*doAPtr) () = &thingA< T >::template doA< 2 >;
>>
>>
>>     
>
> I dind't know that construction, thanks.
>
> --tm
>   

Thanks to John Love-Jensen:

http://gcc.gnu.org/ml/gcc-help/2006-04/msg00023.html

(Sorry for not finding it before posting, I thought I had searched 
exhaustively.)