Re: [boost] [bind] virtual function pointer woes

Subject: Re: [boost] [bind] virtual function pointer woes
From: Chris (indy271828_at_[hidden])
Date: 2009-01-08 14:26:37

As far as I know, no.  If you find a true answer, please tell me.
I had this problem once as well and looked into it on the newsgroups.   
There may be a non-portable way with the vtable and asm, but not 
generally.  My suggestion would be to make a split

_nv function that does the call

struct B     { virtual void f() { f_nv(); }  void f_nv() 
{std::printf("B\n"); } };
struct D : B { virtual void f() { f_nv(); } void f_nv() { 
std::printf("D\n"); } };

And then bind _nv;

Eric Niebler wrote:
> Imagine I have a base class B with a virtual function f() that is 
> overridden in a derived class D ...
>
> struct B     { virtual void f() { std::printf("B\n"); } };
> struct D : B { virtual void f() { std::printf("D\n"); } };
>
> Now, I can have a derived object D and call the base member directly 
> using qualification:
>
> D d;
> d.B::f(); // OK, called B::f
>
> But if I take the address of B::f for use with boost::bind, I get a 
> thunk that always uses virtual dispatch...
>
> boost::bind( &B::f, _1 )( d ); // Hrm, calls D::f
>
> What if I don't want the virtual dispatch, and I really want this to 
> behave like d.B::f()?
>
> I know this is not specifically a problem with boost::bind, but a more 
> general property of (virtual) member function pointers. Is there any 
> way to get a non-virtual member function pointer to a virtual member 
> function? If there is a way, I'm sure I don't know it.
>