Re: [boost] [ptr_container] trunk has problems with multiple definitions of xml_names with multiple TUs

From: Jeff Garland (jeff_at_[hidden])
Date: 2007-11-07 07:30:30

Felipe Magno de Almeida wrote:
> On 11/7/07, Thorsten Ottosen <thorsten.ottosen_at_[hidden]> wrote:
>> Felipe Magno de Almeida skrev:
>>> This gives multiple definition errors when #include'd by more than one
>>> translation unit.
>>>
>>> namespace boost
>>> {
>>>     namespace ptr_container_detail
>>>     {
>>>         const char* count  = "count";
>>>         const char* item   = "item";
>>>         const char* first  = "first";
>>>         const char* second = "second";
>>>     }
>>> }
>> Thanks. Is there an easy way to fix it?
> 
> I couldn't think of anything that wouldn't cause ODR violation.
> 

It's a bit ugly, but you can use templates.  There's an example in 
boost/date_time/time_facet.hpp, but it goes something like this:

   template <class CharT>
   struct ptr_container_stuff {
     public:
       typedef CharT char_type;
       static const char_type count[6];
       static const char_type item[5];
      ...

    };

   template <class CharT>
   const typename ptr_container_stuff<CharT>::char_type
   ptr_container_stuff<CharT>::count[6] = {'f','i','r','s','t'};

   template <class CharT>
   const typename ptr_container_stuff<CharT>::char_type
   ptr_container_stuff<CharT>::item[5] = {'i','t','e','m'};

Jeff