On 21/05/2008, Mike Bird <[EMAIL PROTECTED]> wrote:
> On Wed May 21 2008 20:01:10 Jordi Gutiérrez Hermoso wrote:
>
> > So what's the fix here? Why does a using A::f declaration inside class
> > B not work?
>
>
> There's no f(int) in scope, only int(foo).
No, no, wait. This makes no sense. Consider
class foo{};
class A{
public:
void f(int a ){a++;};
private:
virtual void f(foo a) = 0;
};
class B : public A{
public:
using A::f;
private:
virtual void f(foo a){};
};
int main(){
B b;
int a=0;
b.f(a);
}
versus
class foo{};
class A{
public:
void f(int a ){a++;};
public:
virtual void f(foo a) = 0;
};
class B : public A{
public:
using A::f;
public:
virtual void f(foo a){};
};
int main(){
B b;
int a=0;
b.f(a);
}
The *only* thing that changed is the access specifiers. For some
reason, the name lookup works and it seems that the compiler
understands that "using A::f" means "A::f(int)" when some function is
public but fails when the function is private, and tries instead to
interpret "using A::f" as "A::f(C)". The first example fails to
compile, but the second one does.
> But the best solution is to read up on WHY C++ works this way so
> you can understand the implications that thousands of great minds
> have already pondered.
Well, those great minds seem to be too great for me to fathom, because
I really don't see why it seems here that a function's signature isn't
enough to specify it, and they saw it fit to make sure I couldn't both
I overload and inherit three related but different functions.
C++ isn't perfect, the standard isn't gospel, and I'm beginning to
suspect a bug in gcc.
- Jordi G. H.
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