Verifying if the locale is properly supported by the runtime system

You can check if the LANG/LC_ALL locale is supported properly by using the -i mbcs option of the compilers and runner programs:
$ fglcomp -i mbcs
Charmap          : UTF-8
Multibyte        : yes 
Stateless        : yes
Length Semantics : CHAR

The lines printed with this option indicate if the locale can be supported by the operating system libraries. Here is a short description of each line:

Table 1. fglrun -i mbcs line descriptions
Verification Parameter Description
Charmap This is the normalized IANA name of the character set used by the runtime system to communicate with external components (front-end, I/O of XML files). The mapping from the system locale name to a normalized name is defined in $FGLDIR/etc/charmap.alias.
Multibyte

This line indicates if the character set is multibyte.

Stateless

A few character sets are using an internal state that can change during the character flow. Only stateless character sets can be supported (the value must be 'yes').