Re: lying typedef's

From:
"Bo Persson" <bop@gmb.dk>
Newsgroups:
comp.lang.c++.moderated
Date:
Sun, 5 Jul 2009 21:12:30 CST
Message-ID:
<7bbgsoF21ca23U1@mid.individual.net>
something_fit wrote:

i was writing some code when vc++08 gave me a strange error once i
made a struct inside a namespace of the name of a namespace

have i found a bug in the compiler or is this undefined behavior?
because g++ works as expected

#include <iostream>
#include <exception>

struct dummy{};

namespace people{
struct base{
virtual ~base(){}
void say(){
std::cout << "hello" << std::endl;
}
};
}

namespace foo{
struct bar : public people::base{
};

typedef bar type;

struct people{
struct base{
void say(){
std::cout << "goodbye" << std::endl;
}
};
};
}

namespace generic_foo{

template<class T>
struct bar : public people::base{
};

typedef bar<dummy> type;

struct people{
struct base{
void say(){
std::cout << "goodbye" << std::endl;
}
};
};
}

int main(){
foo::type a;
a.say();
generic_foo::type b;
b.say();
return(0);
}

with vc++08 i get

hello
goodbye

with g++ i get

hello
hello


I believe that this could be an effect of not using two-phase name
lookup properly. MSVC is known for not having implemented this fully.

In the declaration of generic_foo::bar, the base class is
non-dependent and so should be bound at that point. The introduction
of an identical name later is nasty, but I cannot find where that is
forbidden (for namespaces).

I am not totally sure about this though, and would give close to zero
points if this was an assignment. :-)

Bo Persson

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