I'm proposing to make platforms without locale handling to appear to Perl and XS code as if they do have locale handling, albeit with just the single locale "C", with synonym "POSIX". This allows existing applications that use locale to be ported to, say Android, without having to change. v5.20 does some of this now, as it allows one to 'use locale' on machines that don't allow locale handling. The code behaves as if it were in the C locale, as it is available on all machines. But there are platforms that don't even have a setlocale() stub, and so the current solution is not complete. I'm proposing to create a POSIX::setlocale() stub on such platforms. The stub would do nothing except provide a return value. For querying the existing locale, it would return "C"; for changing the locale, it would return failure (undef) unless the new locale were POSIX or C, in which case it would return the string "C", indicating success. We would also have create fake values for the categories passable to setlocale(), so we would define &POSIX::LC_ALL, etc.