Quote from
"C++ Standard Library: A Tutorial and Reference, The"
By Nicolai M. Josuttis[^]
"The
messages facet is used to retrieve internationalized messages from a catalog of messages. This facet is intended primarily to provide a service similar to that of the function
perror(). This function is used in POSIX systems to print a system error message for an error number stored in the global variable
errno. Of course, the service provided by messages is more flexible. Unfortunately, it is not defined very precisely."
Conclusion: You better stop to bother yourself with the question how to use it.