Add comment to fix -Wfallthrough warning

[official-gcc.git] / libstdc++-v3 / src / c++98 / mt_allocator.cc

// Allocator details.

// Copyright (C) 2004-2017 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
// <http://www.gnu.org/licenses/>.

//
// ISO C++ 14882:
//

#include <bits/c++config.h>
#include <ext/concurrence.h>
#include <ext/mt_allocator.h>
#include <cstring>

// The include file is needed for uintptr_t. If this file does not compile,
// check to make sure the target has <stdint.h> and that it provides
// uintptr_t.
#include <stdint.h>

namespace
{
#ifdef __GTHREADS
  struct __freelist
  {
    typedef __gnu_cxx::__pool<true>::_Thread_record _Thread_record;
    _Thread_record*     _M_thread_freelist;
    _Thread_record*     _M_thread_freelist_array;
    size_t              _M_max_threads;
    __gthread_key_t     _M_key;

    ~__freelist()
    {
      if (_M_thread_freelist_array)
        {
          __gthread_key_delete(_M_key);
          ::operator delete(static_cast<void*>(_M_thread_freelist_array));
          _M_thread_freelist = 0;
        }
    }
  };

  __freelist&
  get_freelist()
  {
    static __freelist freelist;
    return freelist;
  }

  __gnu_cxx::__mutex&
  get_freelist_mutex()
  {
    static __gnu_cxx::__mutex freelist_mutex;
    return freelist_mutex;
  }

  static void
  _M_destroy_thread_key(void* __id)
  {
    // Return this thread id record to the front of thread_freelist.
    __freelist& freelist = get_freelist();
    {
      __gnu_cxx::__scoped_lock sentry(get_freelist_mutex());
      uintptr_t _M_id = reinterpret_cast<uintptr_t>(__id);

      typedef __gnu_cxx::__pool<true>::_Thread_record _Thread_record;
      _Thread_record* __tr = &freelist._M_thread_freelist_array[_M_id - 1];
      __tr->_M_next = freelist._M_thread_freelist;
      freelist._M_thread_freelist = __tr;
    }
  }
#endif
} // anonymous namespace

namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

  void
  __pool<false>::_M_destroy() throw()
  {
    if (_M_init && !_M_options._M_force_new)
      {
        for (size_t __n = 0; __n < _M_bin_size; ++__n)
          {
            _Bin_record& __bin = _M_bin[__n];
            while (__bin._M_address)
              {
                _Block_address* __tmp = __bin._M_address->_M_next;
                ::operator delete(__bin._M_address->_M_initial);
                __bin._M_address = __tmp;
              }
            ::operator delete(__bin._M_first);
          }
        ::operator delete(_M_bin);
        ::operator delete(_M_binmap);
      }
  }

  void
  __pool<false>::_M_reclaim_block(char* __p, size_t __bytes) throw ()
  {
    // Round up to power of 2 and figure out which bin to use.
    const size_t __which = _M_binmap[__bytes];
    _Bin_record& __bin = _M_bin[__which];

    char* __c = __p - _M_get_align();
    _Block_record* __block = reinterpret_cast<_Block_record*>(__c);

    // Single threaded application - return to global pool.
    __block->_M_next = __bin._M_first[0];
    __bin._M_first[0] = __block;
  }

  char*
  __pool<false>::_M_reserve_block(size_t __bytes, const size_t __thread_id)
  {
    // Round up to power of 2 and figure out which bin to use.
    const size_t __which = _M_binmap[__bytes];
    _Bin_record& __bin = _M_bin[__which];
    const _Tune& __options = _M_get_options();
    const size_t __bin_size = (__options._M_min_bin << __which)
                               + __options._M_align;
    size_t __block_count = __options._M_chunk_size - sizeof(_Block_address);
    __block_count /= __bin_size;

    // Get a new block dynamically, set it up for use.
    void* __v = ::operator new(__options._M_chunk_size);
    _Block_address* __address = static_cast<_Block_address*>(__v);
    __address->_M_initial = __v;
    __address->_M_next = __bin._M_address;
    __bin._M_address = __address;

    char* __c = static_cast<char*>(__v) + sizeof(_Block_address);
    _Block_record* __block = reinterpret_cast<_Block_record*>(__c);
    __bin._M_first[__thread_id] = __block;
    while (--__block_count > 0)
      {
        __c += __bin_size;
        __block->_M_next = reinterpret_cast<_Block_record*>(__c);
        __block = __block->_M_next;
      }
    __block->_M_next = 0;

    __block = __bin._M_first[__thread_id];
    __bin._M_first[__thread_id] = __block->_M_next;

    // NB: For alignment reasons, we can't use the first _M_align
    // bytes, even when sizeof(_Block_record) < _M_align.
    return reinterpret_cast<char*>(__block) + __options._M_align;
  }

  void
  __pool<false>::_M_initialize()
  {
    // _M_force_new must not change after the first allocate(), which
    // in turn calls this method, so if it's false, it's false forever
    // and we don't need to return here ever again.
    if (_M_options._M_force_new)
      {
        _M_init = true;
        return;
      }

    // Create the bins.
    // Calculate the number of bins required based on _M_max_bytes.
    // _M_bin_size is statically-initialized to one.
    size_t __bin_size = _M_options._M_min_bin;
    while (_M_options._M_max_bytes > __bin_size)
      {
        __bin_size <<= 1;
        ++_M_bin_size;
      }

    // Setup the bin map for quick lookup of the relevant bin.
    const size_t __j = (_M_options._M_max_bytes + 1) * sizeof(_Binmap_type);
    _M_binmap = static_cast<_Binmap_type*>(::operator new(__j));
    _Binmap_type* __bp = _M_binmap;
    _Binmap_type __bin_max = _M_options._M_min_bin;
    _Binmap_type __bint = 0;
    for (_Binmap_type __ct = 0; __ct <= _M_options._M_max_bytes; ++__ct)
      {
        if (__ct > __bin_max)
          {
            __bin_max <<= 1;
            ++__bint;
          }
        *__bp++ = __bint;
      }

    // Initialize _M_bin and its members.
    void* __v = ::operator new(sizeof(_Bin_record) * _M_bin_size);
    _M_bin = static_cast<_Bin_record*>(__v);
    for (size_t __n = 0; __n < _M_bin_size; ++__n)
      {
        _Bin_record& __bin = _M_bin[__n];
        __v = ::operator new(sizeof(_Block_record*));
        __bin._M_first = static_cast<_Block_record**>(__v);
        __bin._M_first[0] = 0;
        __bin._M_address = 0;
      }
    _M_init = true;
  }


#ifdef __GTHREADS
  void
  __pool<true>::_M_destroy() throw()
  {
    if (_M_init && !_M_options._M_force_new)
      {
        if (__gthread_active_p())
          {
            for (size_t __n = 0; __n < _M_bin_size; ++__n)
              {
                _Bin_record& __bin = _M_bin[__n];
                while (__bin._M_address)
                  {
                    _Block_address* __tmp = __bin._M_address->_M_next;
                    ::operator delete(__bin._M_address->_M_initial);
                    __bin._M_address = __tmp;
                  }
                ::operator delete(__bin._M_first);
                ::operator delete(__bin._M_free);
                ::operator delete(__bin._M_used);
                ::operator delete(__bin._M_mutex);
              }
          }
        else
          {
            for (size_t __n = 0; __n < _M_bin_size; ++__n)
              {
                _Bin_record& __bin = _M_bin[__n];
                while (__bin._M_address)
                  {
                    _Block_address* __tmp = __bin._M_address->_M_next;
                    ::operator delete(__bin._M_address->_M_initial);
                    __bin._M_address = __tmp;
                  }
                ::operator delete(__bin._M_first);
              }
          }
        ::operator delete(_M_bin);
        ::operator delete(_M_binmap);
      }
  }

  void
  __pool<true>::_M_reclaim_block(char* __p, size_t __bytes) throw ()
  {
    // Round up to power of 2 and figure out which bin to use.
    const size_t __which = _M_binmap[__bytes];
    const _Bin_record& __bin = _M_bin[__which];

    // Know __p not null, assume valid block.
    char* __c = __p - _M_get_align();
    _Block_record* __block = reinterpret_cast<_Block_record*>(__c);
    if (__gthread_active_p())
      {
        // Calculate the number of records to remove from our freelist:
        // in order to avoid too much contention we wait until the
        // number of records is "high enough".
        const size_t __thread_id = _M_get_thread_id();
        const _Tune& __options = _M_get_options();
        const size_t __limit = (100 * (_M_bin_size - __which)
                                * __options._M_freelist_headroom);

        size_t __remove = __bin._M_free[__thread_id];
        __remove *= __options._M_freelist_headroom;

        // NB: We assume that reads of _Atomic_words are atomic.
        const size_t __max_threads = __options._M_max_threads + 1;
        _Atomic_word* const __reclaimed_base =
          reinterpret_cast<_Atomic_word*>(__bin._M_used + __max_threads);
        const _Atomic_word __reclaimed = __reclaimed_base[__thread_id];
        const size_t __net_used = __bin._M_used[__thread_id] - __reclaimed;

        // NB: For performance sake we don't resync every time, in order
        // to spare atomic ops.  Note that if __reclaimed increased by,
        // say, 1024, since the last sync, it means that the other
        // threads executed the atomic in the else below at least the
        // same number of times (at least, because _M_reserve_block may
        // have decreased the counter), therefore one more cannot hurt.
        if (__reclaimed > 1024)
          {
            __bin._M_used[__thread_id] -= __reclaimed;
            __atomic_add(&__reclaimed_base[__thread_id], -__reclaimed);
          }

        if (__remove >= __net_used)
          __remove -= __net_used;
        else
          __remove = 0;
        if (__remove > __limit && __remove > __bin._M_free[__thread_id])
          {
            _Block_record* __first = __bin._M_first[__thread_id];
            _Block_record* __tmp = __first;
            __remove /= __options._M_freelist_headroom;
            const size_t __removed = __remove;
            while (--__remove > 0)
              __tmp = __tmp->_M_next;
            __bin._M_first[__thread_id] = __tmp->_M_next;
            __bin._M_free[__thread_id] -= __removed;

            __gthread_mutex_lock(__bin._M_mutex);
            __tmp->_M_next = __bin._M_first[0];
            __bin._M_first[0] = __first;
            __bin._M_free[0] += __removed;
            __gthread_mutex_unlock(__bin._M_mutex);
          }

        // Return this block to our list and update counters and
        // owner id as needed.
        if (__block->_M_thread_id == __thread_id)
          --__bin._M_used[__thread_id];
        else
          __atomic_add(&__reclaimed_base[__block->_M_thread_id], 1);

        __block->_M_next = __bin._M_first[__thread_id];
        __bin._M_first[__thread_id] = __block;

        ++__bin._M_free[__thread_id];
      }
    else
      {
        // Not using threads, so single threaded application - return
        // to global pool.
        __block->_M_next = __bin._M_first[0];
        __bin._M_first[0] = __block;
      }
  }

  char*
  __pool<true>::_M_reserve_block(size_t __bytes, const size_t __thread_id)
  {
    // Round up to power of 2 and figure out which bin to use.
    const size_t __which = _M_binmap[__bytes];
    const _Tune& __options = _M_get_options();
    const size_t __bin_size = ((__options._M_min_bin << __which)
                               + __options._M_align);
    size_t __block_count = __options._M_chunk_size - sizeof(_Block_address);
    __block_count /= __bin_size;

    // Are we using threads?
    // - Yes, check if there are free blocks on the global
    //   list. If so, grab up to __block_count blocks in one
    //   lock and change ownership. If the global list is
    //   empty, we allocate a new chunk and add those blocks
    //   directly to our own freelist (with us as owner).
    // - No, all operations are made directly to global pool 0
    //   no need to lock or change ownership but check for free
    //   blocks on global list (and if not add new ones) and
    //   get the first one.
    _Bin_record& __bin = _M_bin[__which];
    _Block_record* __block = 0;
    if (__gthread_active_p())
      {
        // Resync the _M_used counters.
        const size_t __max_threads = __options._M_max_threads + 1;
        _Atomic_word* const __reclaimed_base =
          reinterpret_cast<_Atomic_word*>(__bin._M_used + __max_threads);
        const _Atomic_word __reclaimed = __reclaimed_base[__thread_id];
        __bin._M_used[__thread_id] -= __reclaimed;
        __atomic_add(&__reclaimed_base[__thread_id], -__reclaimed);

        __gthread_mutex_lock(__bin._M_mutex);
        if (__bin._M_first[0] == 0)
          {
            void* __v = ::operator new(__options._M_chunk_size);
            _Block_address* __address = static_cast<_Block_address*>(__v);
            __address->_M_initial = __v;
            __address->_M_next = __bin._M_address;
            __bin._M_address = __address;
            __gthread_mutex_unlock(__bin._M_mutex);

            // No need to hold the lock when we are adding a whole
            // chunk to our own list.
            char* __c = static_cast<char*>(__v) + sizeof(_Block_address);
            __block = reinterpret_cast<_Block_record*>(__c);
            __bin._M_free[__thread_id] = __block_count;
            __bin._M_first[__thread_id] = __block;
            while (--__block_count > 0)
              {
                __c += __bin_size;
                __block->_M_next = reinterpret_cast<_Block_record*>(__c);
                __block = __block->_M_next;
              }
            __block->_M_next = 0;
          }
        else
          {
            // Is the number of required blocks greater than or equal
            // to the number that can be provided by the global free
            // list?
            __bin._M_first[__thread_id] = __bin._M_first[0];
            if (__block_count >= __bin._M_free[0])
              {
                __bin._M_free[__thread_id] = __bin._M_free[0];
                __bin._M_free[0] = 0;
                __bin._M_first[0] = 0;
              }
            else
              {
                __bin._M_free[__thread_id] = __block_count;
                __bin._M_free[0] -= __block_count;
                __block = __bin._M_first[0];
                while (--__block_count > 0)
                  __block = __block->_M_next;
                __bin._M_first[0] = __block->_M_next;
                __block->_M_next = 0;
              }
            __gthread_mutex_unlock(__bin._M_mutex);
          }
      }
    else
      {
        void* __v = ::operator new(__options._M_chunk_size);
        _Block_address* __address = static_cast<_Block_address*>(__v);
        __address->_M_initial = __v;
        __address->_M_next = __bin._M_address;
        __bin._M_address = __address;

        char* __c = static_cast<char*>(__v) + sizeof(_Block_address);
        __block = reinterpret_cast<_Block_record*>(__c);
        __bin._M_first[0] = __block;
        while (--__block_count > 0)
          {
            __c += __bin_size;
            __block->_M_next = reinterpret_cast<_Block_record*>(__c);
            __block = __block->_M_next;
          }
        __block->_M_next = 0;
      }

    __block = __bin._M_first[__thread_id];
    __bin._M_first[__thread_id] = __block->_M_next;

    if (__gthread_active_p())
      {
        __block->_M_thread_id = __thread_id;
        --__bin._M_free[__thread_id];
        ++__bin._M_used[__thread_id];
      }

    // NB: For alignment reasons, we can't use the first _M_align
    // bytes, even when sizeof(_Block_record) < _M_align.
    return reinterpret_cast<char*>(__block) + __options._M_align;
  }

  void
  __pool<true>::_M_initialize()
  {
    // _M_force_new must not change after the first allocate(),
    // which in turn calls this method, so if it's false, it's false
    // forever and we don't need to return here ever again.
    if (_M_options._M_force_new)
      {
        _M_init = true;
        return;
      }

    // Create the bins.
    // Calculate the number of bins required based on _M_max_bytes.
    // _M_bin_size is statically-initialized to one.
    size_t __bin_size = _M_options._M_min_bin;
    while (_M_options._M_max_bytes > __bin_size)
      {
        __bin_size <<= 1;
        ++_M_bin_size;
      }

    // Setup the bin map for quick lookup of the relevant bin.
    const size_t __j = (_M_options._M_max_bytes + 1) * sizeof(_Binmap_type);
    _M_binmap = static_cast<_Binmap_type*>(::operator new(__j));
    _Binmap_type* __bp = _M_binmap;
    _Binmap_type __bin_max = _M_options._M_min_bin;
    _Binmap_type __bint = 0;
    for (_Binmap_type __ct = 0; __ct <= _M_options._M_max_bytes; ++__ct)
      {
        if (__ct > __bin_max)
          {
            __bin_max <<= 1;
            ++__bint;
          }
        *__bp++ = __bint;
      }

    // Initialize _M_bin and its members.
    void* __v = ::operator new(sizeof(_Bin_record) * _M_bin_size);
    _M_bin = static_cast<_Bin_record*>(__v);

    // If __gthread_active_p() create and initialize the list of
    // free thread ids. Single threaded applications use thread id 0
    // directly and have no need for this.
    if (__gthread_active_p())
      {
        __freelist& freelist = get_freelist();
        {
          __gnu_cxx::__scoped_lock sentry(get_freelist_mutex());

          if (!freelist._M_thread_freelist_array
              || freelist._M_max_threads < _M_options._M_max_threads)
            {
              const size_t __k = sizeof(_Thread_record)
                                 * _M_options._M_max_threads;
              __v = ::operator new(__k);
              _M_thread_freelist = static_cast<_Thread_record*>(__v);

              // NOTE! The first assignable thread id is 1 since the
              // global pool uses id 0
              size_t __i;
              for (__i = 1; __i < _M_options._M_max_threads; ++__i)
                {
                  _Thread_record& __tr = _M_thread_freelist[__i - 1];
                  __tr._M_next = &_M_thread_freelist[__i];
                  __tr._M_id = __i;
                }

              // Set last record.
              _M_thread_freelist[__i - 1]._M_next = 0;
              _M_thread_freelist[__i - 1]._M_id = __i;

              if (!freelist._M_thread_freelist_array)
                {
                  // Initialize per thread key to hold pointer to
                  // _M_thread_freelist.
                  __gthread_key_create(&freelist._M_key,
                                       ::_M_destroy_thread_key);
                  freelist._M_thread_freelist = _M_thread_freelist;
                }
              else
                {
                  _Thread_record* _M_old_freelist
                    = freelist._M_thread_freelist;
                  _Thread_record* _M_old_array
                    = freelist._M_thread_freelist_array;
                  freelist._M_thread_freelist
                    = &_M_thread_freelist[_M_old_freelist - _M_old_array];
                  while (_M_old_freelist)
                    {
                      size_t next_id;
                      if (_M_old_freelist->_M_next)
                        next_id = _M_old_freelist->_M_next - _M_old_array;
                      else
                        next_id = freelist._M_max_threads;
                      _M_thread_freelist[_M_old_freelist->_M_id - 1]._M_next
                        = &_M_thread_freelist[next_id];
                      _M_old_freelist = _M_old_freelist->_M_next;
                    }
                  ::operator delete(static_cast<void*>(_M_old_array));
                }
              freelist._M_thread_freelist_array = _M_thread_freelist;
              freelist._M_max_threads = _M_options._M_max_threads;
            }
        }

        const size_t __max_threads = _M_options._M_max_threads + 1;
        for (size_t __n = 0; __n < _M_bin_size; ++__n)
          {
            _Bin_record& __bin = _M_bin[__n];
            __v = ::operator new(sizeof(_Block_record*) * __max_threads);
            std::memset(__v, 0, sizeof(_Block_record*) * __max_threads);
            __bin._M_first = static_cast<_Block_record**>(__v);

            __bin._M_address = 0;

            __v = ::operator new(sizeof(size_t) * __max_threads);
            std::memset(__v, 0, sizeof(size_t) * __max_threads);

            __bin._M_free = static_cast<size_t*>(__v);

            __v = ::operator new(sizeof(size_t) * __max_threads
                                 + sizeof(_Atomic_word) * __max_threads);
            std::memset(__v, 0, (sizeof(size_t) * __max_threads
                                 + sizeof(_Atomic_word) * __max_threads));
            __bin._M_used = static_cast<size_t*>(__v);

            __v = ::operator new(sizeof(__gthread_mutex_t));
            __bin._M_mutex = static_cast<__gthread_mutex_t*>(__v);

#ifdef __GTHREAD_MUTEX_INIT
            {
              // Do not copy a POSIX/gthr mutex once in use.
              __gthread_mutex_t __tmp = __GTHREAD_MUTEX_INIT;
              *__bin._M_mutex = __tmp;
            }
#else
            { __GTHREAD_MUTEX_INIT_FUNCTION(__bin._M_mutex); }
#endif
          }
      }
    else
      {
        for (size_t __n = 0; __n < _M_bin_size; ++__n)
          {
            _Bin_record& __bin = _M_bin[__n];
            __v = ::operator new(sizeof(_Block_record*));
            __bin._M_first = static_cast<_Block_record**>(__v);
            __bin._M_first[0] = 0;
            __bin._M_address = 0;
          }
      }
    _M_init = true;
  }

  size_t
  __pool<true>::_M_get_thread_id()
  {
    // If we have thread support and it's active we check the thread
    // key value and return its id or if it's not set we take the
    // first record from _M_thread_freelist and sets the key and
    // returns its id.
    if (__gthread_active_p())
      {
        __freelist& freelist = get_freelist();
        void* v = __gthread_getspecific(freelist._M_key);
        uintptr_t _M_id = (uintptr_t)v;
        if (_M_id == 0)
          {
            {
              __gnu_cxx::__scoped_lock sentry(get_freelist_mutex());
              if (freelist._M_thread_freelist)
                {
                  _M_id = freelist._M_thread_freelist->_M_id;
                  freelist._M_thread_freelist
                    = freelist._M_thread_freelist->_M_next;
                }
            }

            __gthread_setspecific(freelist._M_key, (void*)_M_id);
          }
        return _M_id >= _M_options._M_max_threads ? 0 : _M_id;
      }

    // Otherwise (no thread support or inactive) all requests are
    // served from the global pool 0.
    return 0;
  }

  // XXX GLIBCXX_ABI Deprecated
  void
  __pool<true>::_M_destroy_thread_key(void*) throw () { }

  // XXX GLIBCXX_ABI Deprecated
  void
  __pool<true>::_M_initialize(__destroy_handler)
  {
    // _M_force_new must not change after the first allocate(),
    // which in turn calls this method, so if it's false, it's false
    // forever and we don't need to return here ever again.
    if (_M_options._M_force_new)
      {
        _M_init = true;
        return;
      }

    // Create the bins.
    // Calculate the number of bins required based on _M_max_bytes.
    // _M_bin_size is statically-initialized to one.
    size_t __bin_size = _M_options._M_min_bin;
    while (_M_options._M_max_bytes > __bin_size)
      {
        __bin_size <<= 1;
        ++_M_bin_size;
      }

    // Setup the bin map for quick lookup of the relevant bin.
    const size_t __j = (_M_options._M_max_bytes + 1) * sizeof(_Binmap_type);
    _M_binmap = static_cast<_Binmap_type*>(::operator new(__j));
    _Binmap_type* __bp = _M_binmap;
    _Binmap_type __bin_max = _M_options._M_min_bin;
    _Binmap_type __bint = 0;
    for (_Binmap_type __ct = 0; __ct <= _M_options._M_max_bytes; ++__ct)
      {
        if (__ct > __bin_max)
          {
            __bin_max <<= 1;
            ++__bint;
          }
        *__bp++ = __bint;
      }

    // Initialize _M_bin and its members.
    void* __v = ::operator new(sizeof(_Bin_record) * _M_bin_size);
    _M_bin = static_cast<_Bin_record*>(__v);

    // If __gthread_active_p() create and initialize the list of
    // free thread ids. Single threaded applications use thread id 0
    // directly and have no need for this.
    if (__gthread_active_p())
      {
        __freelist& freelist = get_freelist();
        {
          __gnu_cxx::__scoped_lock sentry(get_freelist_mutex());

          if (!freelist._M_thread_freelist_array
              || freelist._M_max_threads < _M_options._M_max_threads)
            {
              const size_t __k = sizeof(_Thread_record)
                                 * _M_options._M_max_threads;
              __v = ::operator new(__k);
              _M_thread_freelist = static_cast<_Thread_record*>(__v);

              // NOTE! The first assignable thread id is 1 since the
              // global pool uses id 0
              size_t __i;
              for (__i = 1; __i < _M_options._M_max_threads; ++__i)
                {
                  _Thread_record& __tr = _M_thread_freelist[__i - 1];
                  __tr._M_next = &_M_thread_freelist[__i];
                  __tr._M_id = __i;
                }

              // Set last record.
              _M_thread_freelist[__i - 1]._M_next = 0;
              _M_thread_freelist[__i - 1]._M_id = __i;

              if (!freelist._M_thread_freelist_array)
                {
                  // Initialize per thread key to hold pointer to
                  // _M_thread_freelist.
                  __gthread_key_create(&freelist._M_key,
                                       ::_M_destroy_thread_key);
                  freelist._M_thread_freelist = _M_thread_freelist;
                }
              else
                {
                  _Thread_record* _M_old_freelist
                    = freelist._M_thread_freelist;
                  _Thread_record* _M_old_array
                    = freelist._M_thread_freelist_array;
                  freelist._M_thread_freelist
                    = &_M_thread_freelist[_M_old_freelist - _M_old_array];
                  while (_M_old_freelist)
                    {
                      size_t next_id;
                      if (_M_old_freelist->_M_next)
                        next_id = _M_old_freelist->_M_next - _M_old_array;
                      else
                        next_id = freelist._M_max_threads;
                      _M_thread_freelist[_M_old_freelist->_M_id - 1]._M_next
                        = &_M_thread_freelist[next_id];
                      _M_old_freelist = _M_old_freelist->_M_next;
                    }
                  ::operator delete(static_cast<void*>(_M_old_array));
                }
              freelist._M_thread_freelist_array = _M_thread_freelist;
              freelist._M_max_threads = _M_options._M_max_threads;
            }
        }

        const size_t __max_threads = _M_options._M_max_threads + 1;
        for (size_t __n = 0; __n < _M_bin_size; ++__n)
          {
            _Bin_record& __bin = _M_bin[__n];
            __v = ::operator new(sizeof(_Block_record*) * __max_threads);
            std::memset(__v, 0, sizeof(_Block_record*) * __max_threads);
            __bin._M_first = static_cast<_Block_record**>(__v);

            __bin._M_address = 0;

            __v = ::operator new(sizeof(size_t) * __max_threads);
            std::memset(__v, 0, sizeof(size_t) * __max_threads);
            __bin._M_free = static_cast<size_t*>(__v);

            __v = ::operator new(sizeof(size_t) * __max_threads +
                                 sizeof(_Atomic_word) * __max_threads);
            std::memset(__v, 0, (sizeof(size_t) * __max_threads
                                 + sizeof(_Atomic_word) * __max_threads));
            __bin._M_used = static_cast<size_t*>(__v);

            __v = ::operator new(sizeof(__gthread_mutex_t));
            __bin._M_mutex = static_cast<__gthread_mutex_t*>(__v);

#ifdef __GTHREAD_MUTEX_INIT
            {
              // Do not copy a POSIX/gthr mutex once in use.
              __gthread_mutex_t __tmp = __GTHREAD_MUTEX_INIT;
              *__bin._M_mutex = __tmp;
            }
#else
            { __GTHREAD_MUTEX_INIT_FUNCTION(__bin._M_mutex); }
#endif
          }
      }
    else
      {
        for (size_t __n = 0; __n < _M_bin_size; ++__n)
          {
            _Bin_record& __bin = _M_bin[__n];
            __v = ::operator new(sizeof(_Block_record*));
            __bin._M_first = static_cast<_Block_record**>(__v);
            __bin._M_first[0] = 0;
            __bin._M_address = 0;
          }
      }
    _M_init = true;
  }
#endif

  // Instantiations.
  template class __mt_alloc<char>;
  template class __mt_alloc<wchar_t>;

_GLIBCXX_END_NAMESPACE_VERSION
} // namespace