Re: Pointer to virtual method in child class as template parameter

Hi all,

Could maybe somebody explain why all the compilers (Comeau, GCC, MSVC)
I tested printed error messages similar to

"error: argument of type "void (A::*)()" is incompatible with template
parameter of type "BMethodPointer"
D<&B::doSomething> d;
   ^
"

when compiling the following code snippet.

--
#include <iostream>

class A { // interface
public:
     virtual void doSomething() = 0;

};

class B : public A { }; // extended interface

class C : public B { // implementation
     virtual void doSomething() {
         std::cout << "test";
     }

};

typedef void (B::* BMethodPointer)();

template <BMethodPointer p>
class D {
     D() { // constructor that calls p on a C instance
         C c;
         (c.*p)();
     }

};

int main() {
     BMethodPointer p = &B::doSomething; // this compiles
     C c;
     (c.*p)();
     D<&B::doSomething> d; // but this doesn't}

--

None of the compilers had a problem when the last code line was
commented out.

Is this a language "feature" or a surprisingly common bug?

Thanks for any hint.

Stephan