Re: [Boost-users] BOOST_STATIC_CONST

Subject: Re: [Boost-users] BOOST_STATIC_CONST
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2010-03-12 19:03:01

AMDG

Olivier Tournaire wrote:
> I am currently having problem with a static const class member (in a header
> only project):
>
> // type.hpp
> template< typename Property >
> struct property_base
> {
>     typedef Property type;
> };
>
> struct some_type : property_base< uint32_t >
> {
>     BOOST_STATIC_CONSTANT( type, first_value       = 1 );
>     BOOST_STATIC_CONSTANT( type, second_value  = 2 );
> };
>
> // main.cpp
> #include "type.hpp"
> ...
> int main(int argc, char** argv)
> {
>    BOOST_CHECK_EQUAL( 1     , some_type::first_value );
> }
>
> This produces a link error (g++ 4.3.4): undefined reference to
> some_type::first_value. Everything is fine with visual ...
>
> If I add const some_type::type some_type::first_value; after the struct
> definition, it compiles and links fine. However, would it produce a multiple
> definition link error in some cases?
> Could you please help?
>   

Putting the definition in a header can indeed cause a multiple
definition error.  The definition needs to be in a cpp file.

In Christ,
Steven Watanabe