Re: what is wrong with this code?

From:
"Bo Persson" <bop@gmb.dk>
Newsgroups:
comp.lang.c++.moderated
Date:
Mon, 20 Jul 2009 03:56:42 CST
Message-ID:
<7che5vF24qq35U1@mid.individual.net>
terry wrote:

This code does not compile unless the second call (at
*************) to the template function is commented out. It causes
fatal error C1001: An internal error has occurred in the compiler
in VS2008.

What part of the standard am I violating? Thanks! Is there a work
around? (posted a similar question earlier but perhaps there was
too much verbiage - it would help to know which errors I am making!)

Terry

void f ( void ) {}

struct B
{
    void f ( void ) {}
    typedef void (B::*mfn_t)( void );
};

template <typename T>
void loop( T fn )
{
    fn();
};

int main(int argc, char* argv[])
{
    loop(::f); //loop works OK

    B::mfn_t mfn(&B::f);
    B* pobject = new B;
    ((pobject)->*(mfn)) (); //member function B::f on
instance *pobject can be accessed OK

    //******************************
    loop(((pobject)->*(mfn))); // comment out to get correct
    compilation //******************************

    delete pobject;
    return 0;
}


Not totally obvious, but the Comeau compiler gives a hint:

"line 24: error: a pointer to a bound function
           may only be used to call the function
        loop(pobject->*mfn); // comment out to get correct compilation"

In the call, a few lines up, you use both a pointer to the B object
and a pointer to the member function. In the call to loop() you would
need to pass both a 'this' pointer and a pointer-to-member. This
doesn't seem to work with a single parameter!

Bo Persson

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