Re: Multiple initialization of template static data members?

From:

"Igor Tandetnik" <itandetnik@mvps.org>

Newsgroups:

microsoft.public.vc.language

Date:

Wed, 16 Apr 2008 08:29:42 -0400

Message-ID:

<#D1TO27nIHA.4760@TK2MSFTNGP06.phx.gbl>

"Angel Tsankov" <fn42551@fmi.uni-sofia.bg> wrote in message
news:%235whyv7nIHA.3376@TK2MSFTNGP05.phx.gbl

I just found out that in VC 2005 one can have multiple
initializations of template static data members:

// File1.cpp
template<typename T>
struct C
{
static int const c;
};

template<>
int const C<int>::c = 0;

int main()
{
}

// File2.cpp
template<typename T>
struct C
{
static int const c;
};

template<>
int const C<int>::c = 1;

Does this behaviour comply with the standard?

This program violates One Definition Rule (ODR) and thus exhibits
undefined behavior. No diagnostic required (and in this case, none
given).

OK, I meant this program:

// main.cpp
int main() {}

// c.h
template<typename T>
struct C {static int const c;};

// c.cpp
#include "c.h"
template<>
int const C<int>::c = 0;

// c2.cpp
#include "c.h"
template<>
int const C<int>::c = 1;

I don't see any fundamental difference between your first and second
attempt. Yes, this program violates ODR too, by providing two
specializations of a static memeber of a class template for the same
type, that are not token-for-token identical.
--
With best wishes,
Igor Tandetnik

With sufficient thrust, pigs fly just fine. However, this is not
necessarily a good idea. It is hard to be sure where they are going to
land, and it could be dangerous sitting under them as they fly
overhead. -- RFC 1925