Proposed resolution:

1. Modify [locale.messages]:

   namespace std {
     class messages_base {
     public:
       typedef intunspecified signed integer type catalog;
     };
     ...
   }
   

[ 2011-03-24 Madrid meeting ]

Consensus that this resolution is the direction we would like to see.

[ 2011-03-02: Daniel updates the proposed wording, changing unspecified signed integral type to unspecified signed integer type (We don't want to allow for bool or char) ]

[ 2011-02-24: Chris Jefferson updates the proposed wording, changing unspecified to unspecified signed integral type ]

In [locale.messages], messages_base::catalog is specified to be a typedef to int. This type is subsequently used to open, access and close catalogs.

However, an OS may have catalog/messaging services that are indexed and managed by types other than int. For example POSIX, publishes the following messaging API:

typedef unspecified nl_catd;

nl_catd catopen(const char* name , int oflag);
char*   catgets(nl_catd catd, int set_id, int msg_id, const char* s);
int     catclose(nl_catd catd);

I.e., the catalog is managed with an unspecified type, not necessarily an int. Mac OS uses a void* for nl_catd (which is conforming to the POSIX standard). The current messages_base spec effectively outlaws using the built-in OS messaging service supplied for this very purpose!