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// Threading support -*- C++ -*-
// Copyright (C) 2001, 2002, 2003, 2004 Free Software Foundation, Inc.
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 2, or (at your option)
// any later version.
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING. If not, write to the Free
// Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
// USA.
// As a special exception, you may use this file as part of a free software
// library without restriction. Specifically, if other files instantiate
// templates or use macros or inline functions from this file, or you compile
// this file and link it with other files to produce an executable, this
// file does not by itself cause the resulting executable to be covered by
// the GNU General Public License. This exception does not however
// invalidate any other reasons why the executable file might be covered by
// the GNU General Public License.
* Copyright (c) 1997-1999
* Silicon Graphics Computer Systems, Inc.
* Permission to use, copy, modify, distribute and sell this software
* and its documentation for any purpose is hereby granted without fee,
* provided that the above copyright notice appear in all copies and
* that both that copyright notice and this permission notice appear
* in supporting documentation. Silicon Graphics makes no
* representations about the suitability of this software for any
* purpose. It is provided "as is" without express or implied warranty.
/** @file stl_threads.h
* This is an internal header file, included by other library headers.
* You should not attempt to use it directly.
#ifndef _STL_THREADS_H
#define _STL_THREADS_H 1
#include <cstddef>
// The only supported threading model is GCC's own gthr.h abstraction
// layer.
#include "bits/gthr.h"
namespace __gnu_internal
extern __gthread_mutex_t _GLIBCXX_mutex;
extern __gthread_mutex_t *_GLIBCXX_mutex_address;
extern __gthread_once_t _GLIBCXX_once;
extern void _GLIBCXX_mutex_init(void);
extern void _GLIBCXX_mutex_address_init(void);
} // namespace __gnu_internal
namespace __gnu_cxx
// Locking class. Note that this class *does not have a
// constructor*. It must be initialized either statically, with
// __STL_MUTEX_INITIALIZER, or dynamically, by explicitly calling
// the _M_initialize member function. (This is similar to the ways
// that a pthreads mutex can be initialized.) There are explicit
// member functions for acquiring and releasing the lock.
// There is no constructor because static initialization is
// essential for some uses, and only a class aggregate (see section
// 8.5.1 of the C++ standard) can be initialized that way. That
// means we must have no constructors, no base classes, no virtual
// functions, and no private or protected members.
struct _STL_mutex_lock
// The class must be statically initialized with __STL_MUTEX_INITIALIZER.
volatile int _M_init_flag;
__gthread_once_t _M_once;
__gthread_mutex_t _M_lock;
// There should be no code in this path given the usage rules above.
if (_M_init_flag) return;
if (__gthread_once(&__gnu_internal::_GLIBCXX_once,
__gnu_internal::_GLIBCXX_mutex_init) != 0
&& __gthread_active_p())
abort ();
if (!_M_init_flag)
// Even though we have a global lock, we use __gthread_once to be
// absolutely certain the _M_lock mutex is only initialized once on
// multiprocessor systems.
__gnu_internal::_GLIBCXX_mutex_address = &_M_lock;
if (__gthread_once(&_M_once,
__gnu_internal::_GLIBCXX_mutex_address_init) != 0
&& __gthread_active_p())
_M_init_flag = 1;
if (!_M_init_flag) _M_initialize();
if (!_M_init_flag) _M_initialize();
} // namespace __gnu_cxx