libstdc++-v3/src/c++11/shared_ptr.cc

   1 // Support for pointer abstractions -*- C++ -*-
   2
   3 // Copyright (C) 2011-2018 Free Software Foundation, Inc.
   4 //
   5 // This file is part of the GNU ISO C++ Library.  This library is free
   6 // software; you can redistribute it and/or modify it under the
   7 // terms of the GNU General Public License as published by the
   8 // Free Software Foundation; either version 3, or (at your option)
   9 // any later version.
  10
  11 // This library is distributed in the hope that it will be useful,
  12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 // GNU General Public License for more details.
  15
  16 // Under Section 7 of GPL version 3, you are granted additional
  17 // permissions described in the GCC Runtime Library Exception, version
  18 // 3.1, as published by the Free Software Foundation.
  19
  20 // You should have received a copy of the GNU General Public License and
  21 // a copy of the GCC Runtime Library Exception along with this program;
  22 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23 // <http://www.gnu.org/licenses/>.
  24
  25 #include <memory>
  26
  27 #include "mutex_pool.h"
  28
  29 namespace __gnu_internal _GLIBCXX_VISIBILITY(hidden)
  30 {
  31   /* Returns different instances of __mutex depending on the passed index
  32    * in order to limit contention.
  33    */
  34   __gnu_cxx::__mutex&
  35   get_mutex(unsigned char i)
  36   {
  37     static __gnu_cxx::__mutex m[mask + 1];
  38     return m[i];
  39   }
  40 }
  41
  42 namespace std _GLIBCXX_VISIBILITY(default)
  43 {
  44 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  45
  46   bad_weak_ptr::~bad_weak_ptr() noexcept = default;
  47
  48   char const*
  49   bad_weak_ptr::what() const noexcept
  50   { return "bad_weak_ptr"; }
  51
  52 #ifdef __GTHREADS
  53   namespace
  54   {
  55     inline unsigned char key(const void* addr)
  56     { return _Hash_impl::hash(addr) & __gnu_internal::mask; }
  57   }
  58
  59   _Sp_locker::_Sp_locker(const void* p) noexcept
  60   {
  61     if (__gthread_active_p())
  62       {
  63         _M_key1 = _M_key2 = key(p);
  64         __gnu_internal::get_mutex(_M_key1).lock();
  65       }
  66     else
  67       _M_key1 = _M_key2 = __gnu_internal::invalid;
  68   }
  69
  70   _Sp_locker::_Sp_locker(const void* p1, const void* p2) noexcept
  71   {
  72     if (__gthread_active_p())
  73       {
  74         _M_key1 = key(p1);
  75         _M_key2 = key(p2);
  76         if (_M_key2 < _M_key1)
  77           __gnu_internal::get_mutex(_M_key2).lock();
  78         __gnu_internal::get_mutex(_M_key1).lock();
  79         if (_M_key2 > _M_key1)
  80           __gnu_internal::get_mutex(_M_key2).lock();
  81       }
  82     else
  83       _M_key1 = _M_key2 = __gnu_internal::invalid;
  84   }
  85
  86   _Sp_locker::~_Sp_locker()
  87   {
  88     if (_M_key1 != __gnu_internal::invalid)
  89       {
  90         __gnu_internal::get_mutex(_M_key1).unlock();
  91         if (_M_key2 != _M_key1)
  92           __gnu_internal::get_mutex(_M_key2).unlock();
  93       }
  94   }
  95 #endif
  96
  97 _GLIBCXX_END_NAMESPACE_VERSION
  98 } // namespace