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.\" Copyright (c) 2011 The FreeBSD Foundation
.\" All rights reserved.
.\"
.\" This documentation was written by David Chisnall under sponsorship from
.\" the FreeBSD Foundation.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD$
.\"
.Dd September 17, 2011
.Dt DUPLOCALE 3
.Os
.Sh NAME
.Nm duplocale
.Nd duplicate an locale
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In locale.h
.Ft locale_t
.Fn duplocale "locale_t locale"
.Sh DESCRIPTION
Duplicates an existing
.Fa locale_t
returning a new
.Fa locale_t
that refers to the same locale values but has an independent internal state.
Various functions, such as
.Xr 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
.Fa locale_t
associated with the current thread by
.Xr 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
.Xr freelocale 3 .
.Sh SEE ALSO
.Xr freelocale 3 ,
.Xr localeconv 3 ,
.Xr newlocale 3 ,
.Xr querylocale 3 ,
.Xr uselocale 3 ,
.Xr xlocale 3
.Sh STANDARDS
This function conforms to
.St -p1003.1-2008 .
.Sh BUGS
Ideally,
.Xr uselocale 3
should make a copy of the
.Fa 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.
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