Re: what is wrong here?

["Martin v. Loewis" <martin@mira.isdn.cs.tu-berlin.de>]

> > However, if that was the case: Why is it allowed that two using
> > declarations introduce two functions with identical parameter lists?
> 
> This is just a guess: Maybe because functions can be overloaded, and
> there's no way fro a using declaration to select a subset of the
> declarations of an overloaded function.

That was a rhetorical question, sorry. A declaration of a friend
function is only a re-declaration if there was a prior declaration of
that function as a member of the enclosing namespace.

You seem to assume that a using-declaration makes the functions
denoted members of the namespace. If that was the case, then you would
get violations of the odr. So the logical consequence is that
using-declarations do not declare the functions as namespace members.

Otherwise, is the following text well-formed?

namespace A{void foo(){}}
namespace B{void foo(){}}
namespace C{using A::foo;using B::foo;class Bar{friend void foo();};}

My interpretation is: Yes, it is, but C::foo is not defined, yet.

> > namespace X{ void foo(); }
> > namespace Y{ using X::foo; class Bar{ friend void foo(){} }; }
> 
> > Following your line of reasoning, this should define X::foo. I hope
> > this is not the case, though.
> 
> According to my line of reasoning, this would be invalid because
> X::foo can only be defined in namespace X or in some enclosing
> namespace.  However, I can't seem to find the restriction that a
> non-member function can only be defined in enclosing namepaces in the
> Standard at this very moment; am I mistaken?


It is in 7.3.1.2, [namespace.memdef]/2. However, this rule does not
strictly apply: the member is not defined by explicit qualification.

I still think that the original example

void foo();

namespace B{
  using ::foo;
  class X{
    friend void foo();
    int x;
  };
}

void foo(){
  X x;x.x=3;
}

is ill-formed in standard C++.

Regards,
Martin