duplocale(3)

duplocale3

Duplicate an locale

Usage

#include <locale.h>

locale_t

duplocale(locale_t locale);

Library

Standard C Library (libc, -lc)

Overview

Duplicates an existing locale_t returning a new locale_t that refers to the same locale values but has an independent internal state. Various 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).

Releases

33 releases since FreeBSD 9.1-RELEASE; the text changed 19 times.

  1. 9.1
  2. 9.2
  3. 9.3
  4. 10.0
  5. 10.1
  6. 10.2
  7. 10.3
  8. 10.4
  9. 11.0
  10. 11.1
  11. 11.2
  12. 11.3
  13. 11.4
  14. 12.0
  15. 12.1
  16. 12.2
  17. 12.3
  18. 12.4
  19. 13.0–13.2
  20. 13.3–16.0

Standards

This function conforms to IEEE Std 1003.1-2008 (“POSIX.1”).

Bugs

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.

From base 16.0-CURRENT-20261027-61c70dc16a79 in FreeBSD 16.0-CURRENT (2026-10-27). Parsed by carta from the page's mdoc source.