news@ono.com (?ISO-8859-15?Q?Arnau Rossell  Castell ?) wrote in message news:<P16A9.2835$l84.252136@news.ono.com>...
> I've come across a problem that i've distilled

I'd like all people could distill their problems equally well.

> in this code snippet:
>
> #include<iostream>
>
> struct A
> {
>  virtual int f1(void){return 0;}
>  int f2(void){return 0;}
> };
>
> struct B: public A
> {
>  virtual int f1(void){return 1;}
>  int f2(void){return 1;}
> };
>
> int main(int argc, char* argv[])
> {
>  B test;
>  int(B::*p1)(void),(B::*p2)(void);
>  p1=B::f1;p2=B::f2;
>  std::cout << (test.*p1)() << "\t"<<(test.*p2)() << "\n";
>  std::cout << test.f1() << "\t"<<test.f2() << "\n\n";
>  p1=B::A::f1;p2=B::A::f2;
>  std::cout << (test.*p1)()

Please note that while this piece doesn't work as you expect,

>  << "\t" << (test.*p2)() << "\n";
>  std::cout << test.A::f1()

this piece of code does.

><< "\t" << test.A::f2() << std::endl;
>
>  return 0;
> }
>
> I thought that this program should output something like:
> 1 1
> 1 1
>
> 0 0
> 0 0
>
> But instead it does this:
> 1 1
> 1 1
>
> 1 0
> 0 0
>
> I'm using microsoft visual c++ 7(.net).
> I'd like to know if this is standard behavior, or the compiler is
> wrong(or i've messed something important).

You should have named the subject:
 " ... doesn't work with pointer-to-members to virtual functions"

And now you should understand: When using pointers or pointer-to-members,
you get polymorphic behavior with virtual functions.

With virtual functions, a pointer-to-member can only point to a dynamically
bound function, and the actually called function is determined by the actual
type of the object on which its called.

When you call the function without a pointer-to-member - test.A::f1() -
everything works like you expected.

>
> Thank you in advance.
>
> Arnau Rossell  Castell

HTH,

Uwe

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I've come across a problem that i've distilled in this code snippet:

#include<iostream>

struct A
{
 virtual int f1(void){return 0;}
 int f2(void){return 0;}
};

struct B: public A
{
 virtual int f1(void){return 1;}
 int f2(void){return 1;}
};

int main(int argc, char* argv[])
{
 B test;
 int(B::*p1)(void),(B::*p2)(void);
 p1=3DB::f1;p2=3DB::f2;
 std::cout << (test.*p1)() << "\t"<<(test.*p2)() << "\n";
 std::cout << test.f1() << "\t"<<test.f2() << "\n\n";
 p1=3DB::A::f1;p2=3DB::A::f2;
 std::cout << (test.*p1)() << "\t" << (test.*p2)() << "\n";
 std::cout << test.A::f1() << "\t" << test.A::f2() << std::endl;

 return 0;
}

I thought that this program should output something like:
1 1
1 1

0 0
0 0

But instead it does this:
1 1
1 1

1 0
0 0

I'm using microsoft visual c++ 7(.net).
I'd like to know if this is standard behavior, or the compiler is=20
wrong(or i've messed something important).

Thank you in advance.

Arnau Rossell=F3 Castell=F3

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