DUPLOCALE(3) BSD Library Functions Manual DUPLOCALE(3)
duplocale -- duplicate an locale
Standard C Library (libc, -lc)
Duplicates an existing locale_t returning a new locale_t that refers to the same locale values but has an independent internal state. Vari-
ous functions, such as mblen(3) require a persistent state. These functions formerly used static variables and calls to them from multiple
threads had undefined behavior. They now use fields in the locale_t associated with the current thread by uselocale(3). These calls are
therefore only thread safe on threads with a unique per-thread locale. The locale returned by this call must be freed with freelocale(3).
freelocale(3), localeconv(3), newlocale(3), querylocale(3), uselocale(3), xlocale(3)
This function conforms to IEEE Std 1003.1-2008 (``POSIX.1'').
Ideally, uselocale(3) should make a copy of the locale_t implicitly to ensure thread safety, and a copy of the global locale should be
installed lazily on each thread. The FreeBSD implementation does not do this, for compatibility with Darwin.
September 17, 2011 BSD