Re: anonymous enums and templates

From:

Greg Herlihy <greghe@mac.com>

Newsgroups:

comp.lang.c++.moderated

Date:

Sat, 12 Apr 2008 12:13:11 CST

Message-ID:

<10133584-318a-4d96-bb5b-b07ad9ce29f5@q1g2000prf.googlegroups.com>

On Apr 11, 10:34 am, "Roman.Perepeli...@gmail.com"
<Roman.Perepeli...@gmail.com> wrote:

Is this program valid? Why? If yes then what it prints?

#include <iostream>

enum { value };

template <class T>
int f(T) { return 1; }

int f(int) { return 2; }

int main()
{
std::cout << f(value) << std::endl;
}

No, the program above is not valid because the best match for the f()
function call in main is a function template that cannot legally be
instantiated. In particular, the anonymous enumerated type that would
instantiate f() does not have external linkage.

One solution would be to give value's anonymous enumerated type a
name. Another solution would avoid instantiating the f() function
template - by making f(int) a better match for the f() function call
in main:

     std::cout << f(int(value)) << "\n";

Greg

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