<h2>Editing File: /usr/include/c++/8/mutex</h2><form method='post'><textarea name='content' class='file-edit'>// &lt;mutex&gt; -*- C++ -*-

// Copyright (C) 2003-2018 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 3, 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
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// &lt;http://www.gnu.org/licenses/&gt;.

/** @file include/mutex
 *  This is a Standard C++ Library header.
 */

#ifndef _GLIBCXX_MUTEX
#define _GLIBCXX_MUTEX 1

#pragma GCC system_header

#if __cplusplus &lt; 201103L
# include &lt;bits/c++0x_warning.h&gt;
#else

#include &lt;tuple&gt;
#include &lt;chrono&gt;
#include &lt;exception&gt;
#include &lt;type_traits&gt;
#include &lt;system_error&gt;
#include &lt;bits/std_mutex.h&gt;
#if ! _GTHREAD_USE_MUTEX_TIMEDLOCK
# include &lt;condition_variable&gt;
# include &lt;thread&gt;
#endif
#ifndef _GLIBCXX_HAVE_TLS
# include &lt;bits/std_function.h&gt;
#endif

#ifdef _GLIBCXX_USE_C99_STDINT_TR1

namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

  /**
   * @ingroup mutexes
   * @{
   */

#ifdef _GLIBCXX_HAS_GTHREADS

  // Common base class for std::recursive_mutex and std::recursive_timed_mutex
  class __recursive_mutex_base
  {
  protected:
    typedef __gthread_recursive_mutex_t		__native_type;

    __recursive_mutex_base(const __recursive_mutex_base&amp;) = delete;
    __recursive_mutex_base&amp; operator=(const __recursive_mutex_base&amp;) = delete;

#ifdef __GTHREAD_RECURSIVE_MUTEX_INIT
    __native_type  _M_mutex = __GTHREAD_RECURSIVE_MUTEX_INIT;

    __recursive_mutex_base() = default;
#else
    __native_type  _M_mutex;

    __recursive_mutex_base()
    {
      // XXX EAGAIN, ENOMEM, EPERM, EBUSY(may), EINVAL(may)
      __GTHREAD_RECURSIVE_MUTEX_INIT_FUNCTION(&amp;_M_mutex);
    }

    ~__recursive_mutex_base()
    { __gthread_recursive_mutex_destroy(&amp;_M_mutex); }
#endif
  };

  /// The standard recursive mutex type.
  class recursive_mutex : private __recursive_mutex_base
  {
  public:
    typedef __native_type* 			native_handle_type;

    recursive_mutex() = default;
    ~recursive_mutex() = default;

    recursive_mutex(const recursive_mutex&amp;) = delete;
    recursive_mutex&amp; operator=(const recursive_mutex&amp;) = delete;

    void
    lock()
    {
      int __e = __gthread_recursive_mutex_lock(&amp;_M_mutex);

      // EINVAL, EAGAIN, EBUSY, EINVAL, EDEADLK(may)
      if (__e)
	__throw_system_error(__e);
    }

    bool
    try_lock() noexcept
    {
      // XXX EINVAL, EAGAIN, EBUSY
      return !__gthread_recursive_mutex_trylock(&amp;_M_mutex);
    }

    void
    unlock()
    {
      // XXX EINVAL, EAGAIN, EBUSY
      __gthread_recursive_mutex_unlock(&amp;_M_mutex);
    }

    native_handle_type
    native_handle() noexcept
    { return &amp;_M_mutex; }
  };

#if _GTHREAD_USE_MUTEX_TIMEDLOCK
  template&lt;typename _Derived&gt;
    class __timed_mutex_impl
    {
    protected:
      typedef chrono::high_resolution_clock 	__clock_t;

      template&lt;typename _Rep, typename _Period&gt;
	bool
	_M_try_lock_for(const chrono::duration&lt;_Rep, _Period&gt;&amp; __rtime)
	{
	  using chrono::steady_clock;
	  auto __rt = chrono::duration_cast&lt;steady_clock::duration&gt;(__rtime);
	  if (ratio_greater&lt;steady_clock::period, _Period&gt;())
	    ++__rt;
	  return _M_try_lock_until(steady_clock::now() + __rt);
	}

      template&lt;typename _Duration&gt;
	bool
	_M_try_lock_until(const chrono::time_point&lt;__clock_t,
						   _Duration&gt;&amp; __atime)
	{
	  auto __s = chrono::time_point_cast&lt;chrono::seconds&gt;(__atime);
	  auto __ns = chrono::duration_cast&lt;chrono::nanoseconds&gt;(__atime - __s);

	  __gthread_time_t __ts = {
	    static_cast&lt;std::time_t&gt;(__s.time_since_epoch().count()),
	    static_cast&lt;long&gt;(__ns.count())
	  };

	  return static_cast&lt;_Derived*&gt;(this)-&gt;_M_timedlock(__ts);
	}

      template&lt;typename _Clock, typename _Duration&gt;
	bool
	_M_try_lock_until(const chrono::time_point&lt;_Clock, _Duration&gt;&amp; __atime)
	{
	  auto __rtime = __atime - _Clock::now();
	  return _M_try_lock_until(__clock_t::now() + __rtime);
	}
    };

  /// The standard timed mutex type.
  class timed_mutex
  : private __mutex_base, public __timed_mutex_impl&lt;timed_mutex&gt;
  {
  public:
    typedef __native_type* 		  	native_handle_type;

    timed_mutex() = default;
    ~timed_mutex() = default;

    timed_mutex(const timed_mutex&amp;) = delete;
    timed_mutex&amp; operator=(const timed_mutex&amp;) = delete;

    void
    lock()
    {
      int __e = __gthread_mutex_lock(&amp;_M_mutex);

      // EINVAL, EAGAIN, EBUSY, EINVAL, EDEADLK(may)
      if (__e)
	__throw_system_error(__e);
    }

    bool
    try_lock() noexcept
    {
      // XXX EINVAL, EAGAIN, EBUSY
      return !__gthread_mutex_trylock(&amp;_M_mutex);
    }

    template &lt;class _Rep, class _Period&gt;
      bool
      try_lock_for(const chrono::duration&lt;_Rep, _Period&gt;&amp; __rtime)
      { return _M_try_lock_for(__rtime); }

    template &lt;class _Clock, class _Duration&gt;
      bool
      try_lock_until(const chrono::time_point&lt;_Clock, _Duration&gt;&amp; __atime)
      { return _M_try_lock_until(__atime); }

    void
    unlock()
    {
      // XXX EINVAL, EAGAIN, EBUSY
      __gthread_mutex_unlock(&amp;_M_mutex);
    }

    native_handle_type
    native_handle() noexcept
    { return &amp;_M_mutex; }

    private:
      friend class __timed_mutex_impl&lt;timed_mutex&gt;;

      bool
      _M_timedlock(const __gthread_time_t&amp; __ts)
      { return !__gthread_mutex_timedlock(&amp;_M_mutex, &amp;__ts); }
  };

  /// recursive_timed_mutex
  class recursive_timed_mutex
  : private __recursive_mutex_base,
    public __timed_mutex_impl&lt;recursive_timed_mutex&gt;
  {
  public:
    typedef __native_type* 			native_handle_type;

    recursive_timed_mutex() = default;
    ~recursive_timed_mutex() = default;

    recursive_timed_mutex(const recursive_timed_mutex&amp;) = delete;
    recursive_timed_mutex&amp; operator=(const recursive_timed_mutex&amp;) = delete;

    void
    lock()
    {
      int __e = __gthread_recursive_mutex_lock(&amp;_M_mutex);

      // EINVAL, EAGAIN, EBUSY, EINVAL, EDEADLK(may)
      if (__e)
	__throw_system_error(__e);
    }

    bool
    try_lock() noexcept
    {
      // XXX EINVAL, EAGAIN, EBUSY
      return !__gthread_recursive_mutex_trylock(&amp;_M_mutex);
    }

    template &lt;class _Rep, class _Period&gt;
      bool
      try_lock_for(const chrono::duration&lt;_Rep, _Period&gt;&amp; __rtime)
      { return _M_try_lock_for(__rtime); }

    template &lt;class _Clock, class _Duration&gt;
      bool
      try_lock_until(const chrono::time_point&lt;_Clock, _Duration&gt;&amp; __atime)
      { return _M_try_lock_until(__atime); }

    void
    unlock()
    {
      // XXX EINVAL, EAGAIN, EBUSY
      __gthread_recursive_mutex_unlock(&amp;_M_mutex);
    }

    native_handle_type
    native_handle() noexcept
    { return &amp;_M_mutex; }

    private:
      friend class __timed_mutex_impl&lt;recursive_timed_mutex&gt;;

      bool
      _M_timedlock(const __gthread_time_t&amp; __ts)
      { return !__gthread_recursive_mutex_timedlock(&amp;_M_mutex, &amp;__ts); }
  };

#else // !_GTHREAD_USE_MUTEX_TIMEDLOCK

  /// timed_mutex
  class timed_mutex
  {
    mutex		_M_mut;
    condition_variable	_M_cv;
    bool		_M_locked = false;

  public:

    timed_mutex() = default;
    ~timed_mutex() { __glibcxx_assert( !_M_locked ); }

    timed_mutex(const timed_mutex&amp;) = delete;
    timed_mutex&amp; operator=(const timed_mutex&amp;) = delete;

    void
    lock()
    {
      unique_lock&lt;mutex&gt; __lk(_M_mut);
      _M_cv.wait(__lk, [&amp;]{ return !_M_locked; });
      _M_locked = true;
    }

    bool
    try_lock()
    {
      lock_guard&lt;mutex&gt; __lk(_M_mut);
      if (_M_locked)
	return false;
      _M_locked = true;
      return true;
    }

    template&lt;typename _Rep, typename _Period&gt;
      bool
      try_lock_for(const chrono::duration&lt;_Rep, _Period&gt;&amp; __rtime)
      {
	unique_lock&lt;mutex&gt; __lk(_M_mut);
	if (!_M_cv.wait_for(__lk, __rtime, [&amp;]{ return !_M_locked; }))
	  return false;
	_M_locked = true;
	return true;
      }

    template&lt;typename _Clock, typename _Duration&gt;
      bool
      try_lock_until(const chrono::time_point&lt;_Clock, _Duration&gt;&amp; __atime)
      {
	unique_lock&lt;mutex&gt; __lk(_M_mut);
	if (!_M_cv.wait_until(__lk, __atime, [&amp;]{ return !_M_locked; }))
	  return false;
	_M_locked = true;
	return true;
      }

    void
    unlock()
    {
      lock_guard&lt;mutex&gt; __lk(_M_mut);
      __glibcxx_assert( _M_locked );
      _M_locked = false;
      _M_cv.notify_one();
    }
  };

  /// recursive_timed_mutex
  class recursive_timed_mutex
  {
    mutex		_M_mut;
    condition_variable	_M_cv;
    thread::id		_M_owner;
    unsigned		_M_count = 0;

    // Predicate type that tests whether the current thread can lock a mutex.
    struct _Can_lock
    {
      // Returns true if the mutex is unlocked or is locked by _M_caller.
      bool
      operator()() const noexcept
      { return _M_mx-&gt;_M_count == 0 || _M_mx-&gt;_M_owner == _M_caller; }

      const recursive_timed_mutex* _M_mx;
      thread::id _M_caller;
    };

  public:

    recursive_timed_mutex() = default;
    ~recursive_timed_mutex() { __glibcxx_assert( _M_count == 0 ); }

    recursive_timed_mutex(const recursive_timed_mutex&amp;) = delete;
    recursive_timed_mutex&amp; operator=(const recursive_timed_mutex&amp;) = delete;

    void
    lock()
    {
      auto __id = this_thread::get_id();
      _Can_lock __can_lock{this, __id};
      unique_lock&lt;mutex&gt; __lk(_M_mut);
      _M_cv.wait(__lk, __can_lock);
      if (_M_count == -1u)
	__throw_system_error(EAGAIN); // [thread.timedmutex.recursive]/3
      _M_owner = __id;
      ++_M_count;
    }

    bool
    try_lock()
    {
      auto __id = this_thread::get_id();
      _Can_lock __can_lock{this, __id};
      lock_guard&lt;mutex&gt; __lk(_M_mut);
      if (!__can_lock())
	return false;
      if (_M_count == -1u)
	return false;
      _M_owner = __id;
      ++_M_count;
      return true;
    }

    template&lt;typename _Rep, typename _Period&gt;
      bool
      try_lock_for(const chrono::duration&lt;_Rep, _Period&gt;&amp; __rtime)
      {
	auto __id = this_thread::get_id();
	_Can_lock __can_lock{this, __id};
	unique_lock&lt;mutex&gt; __lk(_M_mut);
	if (!_M_cv.wait_for(__lk, __rtime, __can_lock))
	  return false;
	if (_M_count == -1u)
	  return false;
	_M_owner = __id;
	++_M_count;
	return true;
      }

    template&lt;typename _Clock, typename _Duration&gt;
      bool
      try_lock_until(const chrono::time_point&lt;_Clock, _Duration&gt;&amp; __atime)
      {
	auto __id = this_thread::get_id();
	_Can_lock __can_lock{this, __id};
	unique_lock&lt;mutex&gt; __lk(_M_mut);
	if (!_M_cv.wait_until(__lk, __atime, __can_lock))
	  return false;
	if (_M_count == -1u)
	  return false;
	_M_owner = __id;
	++_M_count;
	return true;
      }

    void
    unlock()
    {
      lock_guard&lt;mutex&gt; __lk(_M_mut);
      __glibcxx_assert( _M_owner == this_thread::get_id() );
      __glibcxx_assert( _M_count &gt; 0 );
      if (--_M_count == 0)
	{
	  _M_owner = {};
	  _M_cv.notify_one();
	}
    }
  };

#endif
#endif // _GLIBCXX_HAS_GTHREADS

  template&lt;typename _Lock&gt;
    inline unique_lock&lt;_Lock&gt;
    __try_to_lock(_Lock&amp; __l)
    { return unique_lock&lt;_Lock&gt;{__l, try_to_lock}; }

  template&lt;int _Idx, bool _Continue = true&gt;
    struct __try_lock_impl
    {
      template&lt;typename... _Lock&gt;
	static void
	__do_try_lock(tuple&lt;_Lock&amp;...&gt;&amp; __locks, int&amp; __idx)
	{
          __idx = _Idx;
          auto __lock = std::__try_to_lock(std::get&lt;_Idx&gt;(__locks));
          if (__lock.owns_lock())
            {
	      constexpr bool __cont = _Idx + 2 &lt; sizeof...(_Lock);
	      using __try_locker = __try_lock_impl&lt;_Idx + 1, __cont&gt;;
	      __try_locker::__do_try_lock(__locks, __idx);
              if (__idx == -1)
                __lock.release();
            }
	}
    };

  template&lt;int _Idx&gt;
    struct __try_lock_impl&lt;_Idx, false&gt;
    {
      template&lt;typename... _Lock&gt;
	static void
	__do_try_lock(tuple&lt;_Lock&amp;...&gt;&amp; __locks, int&amp; __idx)
	{
          __idx = _Idx;
          auto __lock = std::__try_to_lock(std::get&lt;_Idx&gt;(__locks));
          if (__lock.owns_lock())
            {
              __idx = -1;
              __lock.release();
            }
	}
    };

  /** @brief Generic try_lock.
   *  @param __l1 Meets Lockable requirements (try_lock() may throw).
   *  @param __l2 Meets Lockable requirements (try_lock() may throw).
   *  @param __l3 Meets Lockable requirements (try_lock() may throw).
   *  @return Returns -1 if all try_lock() calls return true. Otherwise returns
   *          a 0-based index corresponding to the argument that returned false.
   *  @post Either all arguments are locked, or none will be.
   *
   *  Sequentially calls try_lock() on each argument.
   */
  template&lt;typename _Lock1, typename _Lock2, typename... _Lock3&gt;
    int
    try_lock(_Lock1&amp; __l1, _Lock2&amp; __l2, _Lock3&amp;... __l3)
    {
      int __idx;
      auto __locks = std::tie(__l1, __l2, __l3...);
      __try_lock_impl&lt;0&gt;::__do_try_lock(__locks, __idx);
      return __idx;
    }

  /** @brief Generic lock.
   *  @param __l1 Meets Lockable requirements (try_lock() may throw).
   *  @param __l2 Meets Lockable requirements (try_lock() may throw).
   *  @param __l3 Meets Lockable requirements (try_lock() may throw).
   *  @throw An exception thrown by an argument's lock() or try_lock() member.
   *  @post All arguments are locked.
   *
   *  All arguments are locked via a sequence of calls to lock(), try_lock()
   *  and unlock().  If the call exits via an exception any locks that were
   *  obtained will be released.
   */
  template&lt;typename _L1, typename _L2, typename... _L3&gt;
    void
    lock(_L1&amp; __l1, _L2&amp; __l2, _L3&amp;... __l3)
    {
      while (true)
        {
          using __try_locker = __try_lock_impl&lt;0, sizeof...(_L3) != 0&gt;;
          unique_lock&lt;_L1&gt; __first(__l1);
          int __idx;
          auto __locks = std::tie(__l2, __l3...);
          __try_locker::__do_try_lock(__locks, __idx);
          if (__idx == -1)
            {
              __first.release();
              return;
            }
        }
    }

#if __cplusplus &gt;= 201703L
#define __cpp_lib_scoped_lock 201703
  /** @brief A scoped lock type for multiple lockable objects.
   *
   * A scoped_lock controls mutex ownership within a scope, releasing
   * ownership in the destructor.
   */
  template&lt;typename... _MutexTypes&gt;
    class scoped_lock
    {
    public:
      explicit scoped_lock(_MutexTypes&amp;... __m) : _M_devices(std::tie(__m...))
      { std::lock(__m...); }

      explicit scoped_lock(adopt_lock_t, _MutexTypes&amp;... __m) noexcept
      : _M_devices(std::tie(__m...))
      { } // calling thread owns mutex

      ~scoped_lock()
      {
	std::apply([](_MutexTypes&amp;... __m) {
	  char __i[] __attribute__((__unused__)) = { (__m.unlock(), 0)... };
	}, _M_devices);
      }

      scoped_lock(const scoped_lock&amp;) = delete;
      scoped_lock&amp; operator=(const scoped_lock&amp;) = delete;

    private:
      tuple&lt;_MutexTypes&amp;...&gt; _M_devices;
    };

  template&lt;&gt;
    class scoped_lock&lt;&gt;
    {
    public:
      explicit scoped_lock() = default;
      explicit scoped_lock(adopt_lock_t) noexcept { }
      ~scoped_lock() = default;

      scoped_lock(const scoped_lock&amp;) = delete;
      scoped_lock&amp; operator=(const scoped_lock&amp;) = delete;
    };

  template&lt;typename _Mutex&gt;
    class scoped_lock&lt;_Mutex&gt;
    {
    public:
      using mutex_type = _Mutex;

      explicit scoped_lock(mutex_type&amp; __m) : _M_device(__m)
      { _M_device.lock(); }

      explicit scoped_lock(adopt_lock_t, mutex_type&amp; __m) noexcept
      : _M_device(__m)
      { } // calling thread owns mutex

      ~scoped_lock()
      { _M_device.unlock(); }

      scoped_lock(const scoped_lock&amp;) = delete;
      scoped_lock&amp; operator=(const scoped_lock&amp;) = delete;

    private:
      mutex_type&amp;  _M_device;
    };
#endif // C++17

#ifdef _GLIBCXX_HAS_GTHREADS
  /// once_flag
  struct once_flag
  {
  private:
    typedef __gthread_once_t __native_type;
    __native_type  _M_once = __GTHREAD_ONCE_INIT;

  public:
    /// Constructor
    constexpr once_flag() noexcept = default;

    /// Deleted copy constructor
    once_flag(const once_flag&amp;) = delete;
    /// Deleted assignment operator
    once_flag&amp; operator=(const once_flag&amp;) = delete;

    template&lt;typename _Callable, typename... _Args&gt;
      friend void
      call_once(once_flag&amp; __once, _Callable&amp;&amp; __f, _Args&amp;&amp;... __args);
  };

#ifdef _GLIBCXX_HAVE_TLS
  extern __thread void* __once_callable;
  extern __thread void (*__once_call)();
#else
  extern function&lt;void()&gt; __once_functor;

  extern void
  __set_once_functor_lock_ptr(unique_lock&lt;mutex&gt;*);

  extern mutex&amp;
  __get_once_mutex();
#endif

  extern &quot;C&quot; void __once_proxy(void);

  /// call_once
  template&lt;typename _Callable, typename... _Args&gt;
    void
    call_once(once_flag&amp; __once, _Callable&amp;&amp; __f, _Args&amp;&amp;... __args)
    {
      // _GLIBCXX_RESOLVE_LIB_DEFECTS
      // 2442. call_once() shouldn't DECAY_COPY()
      auto __callable = [&amp;] {
	  std::__invoke(std::forward&lt;_Callable&gt;(__f),
			std::forward&lt;_Args&gt;(__args)...);
      };
#ifdef _GLIBCXX_HAVE_TLS
      __once_callable = std::__addressof(__callable); // NOLINT: PR 82481
      __once_call = []{ (*(decltype(__callable)*)__once_callable)(); };
#else
      unique_lock&lt;mutex&gt; __functor_lock(__get_once_mutex());
      __once_functor = __callable;
      __set_once_functor_lock_ptr(&amp;__functor_lock);
#endif

      int __e = __gthread_once(&amp;__once._M_once, &amp;__once_proxy);

#ifndef _GLIBCXX_HAVE_TLS
      if (__functor_lock)
        __set_once_functor_lock_ptr(0);
#endif

      if (__e)
	__throw_system_error(__e);
    }
#endif // _GLIBCXX_HAS_GTHREADS

  // @} group mutexes
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace
#endif // _GLIBCXX_USE_C99_STDINT_TR1

#endif // C++11

#endif // _GLIBCXX_MUTEX
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