libstdc++
mt_allocator.h
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1 // MT-optimized allocator -*- C++ -*-
2 
3 // Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011
4 // Free Software Foundation, Inc.
5 //
6 // This file is part of the GNU ISO C++ Library. This library is free
7 // software; you can redistribute it and/or modify it under the
8 // terms of the GNU General Public License as published by the
9 // Free Software Foundation; either version 3, or (at your option)
10 // any later version.
11 
12 // This library is distributed in the hope that it will be useful,
13 // but WITHOUT ANY WARRANTY; without even the implied warranty of
14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 // GNU General Public License for more details.
16 
17 // Under Section 7 of GPL version 3, you are granted additional
18 // permissions described in the GCC Runtime Library Exception, version
19 // 3.1, as published by the Free Software Foundation.
20 
21 // You should have received a copy of the GNU General Public License and
22 // a copy of the GCC Runtime Library Exception along with this program;
23 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
24 // <http://www.gnu.org/licenses/>.
25 
26 /** @file ext/mt_allocator.h
27  * This file is a GNU extension to the Standard C++ Library.
28  */
29 
30 #ifndef _MT_ALLOCATOR_H
31 #define _MT_ALLOCATOR_H 1
32 
33 #include <new>
34 #include <cstdlib>
35 #include <bits/functexcept.h>
36 #include <ext/atomicity.h>
37 #include <bits/move.h>
38 
39 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
40 {
41 _GLIBCXX_BEGIN_NAMESPACE_VERSION
42 
43  using std::size_t;
44  using std::ptrdiff_t;
45 
46  typedef void (*__destroy_handler)(void*);
47 
48  /// Base class for pool object.
49  struct __pool_base
50  {
51  // Using short int as type for the binmap implies we are never
52  // caching blocks larger than 32768 with this allocator.
53  typedef unsigned short int _Binmap_type;
54 
55  // Variables used to configure the behavior of the allocator,
56  // assigned and explained in detail below.
57  struct _Tune
58  {
59  // Compile time constants for the default _Tune values.
60  enum { _S_align = 8 };
61  enum { _S_max_bytes = 128 };
62  enum { _S_min_bin = 8 };
63  enum { _S_chunk_size = 4096 - 4 * sizeof(void*) };
64  enum { _S_max_threads = 4096 };
65  enum { _S_freelist_headroom = 10 };
66 
67  // Alignment needed.
68  // NB: In any case must be >= sizeof(_Block_record), that
69  // is 4 on 32 bit machines and 8 on 64 bit machines.
70  size_t _M_align;
71 
72  // Allocation requests (after round-up to power of 2) below
73  // this value will be handled by the allocator. A raw new/
74  // call will be used for requests larger than this value.
75  // NB: Must be much smaller than _M_chunk_size and in any
76  // case <= 32768.
77  size_t _M_max_bytes;
78 
79  // Size in bytes of the smallest bin.
80  // NB: Must be a power of 2 and >= _M_align (and of course
81  // much smaller than _M_max_bytes).
82  size_t _M_min_bin;
83 
84  // In order to avoid fragmenting and minimize the number of
85  // new() calls we always request new memory using this
86  // value. Based on previous discussions on the libstdc++
87  // mailing list we have chosen the value below.
88  // See http://gcc.gnu.org/ml/libstdc++/2001-07/msg00077.html
89  // NB: At least one order of magnitude > _M_max_bytes.
90  size_t _M_chunk_size;
91 
92  // The maximum number of supported threads. For
93  // single-threaded operation, use one. Maximum values will
94  // vary depending on details of the underlying system. (For
95  // instance, Linux 2.4.18 reports 4070 in
96  // /proc/sys/kernel/threads-max, while Linux 2.6.6 reports
97  // 65534)
98  size_t _M_max_threads;
99 
100  // Each time a deallocation occurs in a threaded application
101  // we make sure that there are no more than
102  // _M_freelist_headroom % of used memory on the freelist. If
103  // the number of additional records is more than
104  // _M_freelist_headroom % of the freelist, we move these
105  // records back to the global pool.
106  size_t _M_freelist_headroom;
107 
108  // Set to true forces all allocations to use new().
109  bool _M_force_new;
110 
111  explicit
112  _Tune()
113  : _M_align(_S_align), _M_max_bytes(_S_max_bytes), _M_min_bin(_S_min_bin),
114  _M_chunk_size(_S_chunk_size), _M_max_threads(_S_max_threads),
115  _M_freelist_headroom(_S_freelist_headroom),
116  _M_force_new(std::getenv("GLIBCXX_FORCE_NEW") ? true : false)
117  { }
118 
119  explicit
120  _Tune(size_t __align, size_t __maxb, size_t __minbin, size_t __chunk,
121  size_t __maxthreads, size_t __headroom, bool __force)
122  : _M_align(__align), _M_max_bytes(__maxb), _M_min_bin(__minbin),
123  _M_chunk_size(__chunk), _M_max_threads(__maxthreads),
124  _M_freelist_headroom(__headroom), _M_force_new(__force)
125  { }
126  };
127 
128  struct _Block_address
129  {
130  void* _M_initial;
131  _Block_address* _M_next;
132  };
133 
134  const _Tune&
135  _M_get_options() const
136  { return _M_options; }
137 
138  void
139  _M_set_options(_Tune __t)
140  {
141  if (!_M_init)
142  _M_options = __t;
143  }
144 
145  bool
146  _M_check_threshold(size_t __bytes)
147  { return __bytes > _M_options._M_max_bytes || _M_options._M_force_new; }
148 
149  size_t
150  _M_get_binmap(size_t __bytes)
151  { return _M_binmap[__bytes]; }
152 
153  size_t
154  _M_get_align()
155  { return _M_options._M_align; }
156 
157  explicit
158  __pool_base()
159  : _M_options(_Tune()), _M_binmap(0), _M_init(false) { }
160 
161  explicit
162  __pool_base(const _Tune& __options)
163  : _M_options(__options), _M_binmap(0), _M_init(false) { }
164 
165  private:
166  explicit
167  __pool_base(const __pool_base&);
168 
169  __pool_base&
170  operator=(const __pool_base&);
171 
172  protected:
173  // Configuration options.
174  _Tune _M_options;
175 
176  _Binmap_type* _M_binmap;
177 
178  // Configuration of the pool object via _M_options can happen
179  // after construction but before initialization. After
180  // initialization is complete, this variable is set to true.
181  bool _M_init;
182  };
183 
184 
185  /**
186  * @brief Data describing the underlying memory pool, parameterized on
187  * threading support.
188  */
189  template<bool _Thread>
190  class __pool;
191 
192  /// Specialization for single thread.
193  template<>
194  class __pool<false> : public __pool_base
195  {
196  public:
197  union _Block_record
198  {
199  // Points to the block_record of the next free block.
200  _Block_record* _M_next;
201  };
202 
203  struct _Bin_record
204  {
205  // An "array" of pointers to the first free block.
206  _Block_record** _M_first;
207 
208  // A list of the initial addresses of all allocated blocks.
209  _Block_address* _M_address;
210  };
211 
212  void
213  _M_initialize_once()
214  {
215  if (__builtin_expect(_M_init == false, false))
216  _M_initialize();
217  }
218 
219  void
220  _M_destroy() throw();
221 
222  char*
223  _M_reserve_block(size_t __bytes, const size_t __thread_id);
224 
225  void
226  _M_reclaim_block(char* __p, size_t __bytes) throw ();
227 
228  size_t
229  _M_get_thread_id() { return 0; }
230 
231  const _Bin_record&
232  _M_get_bin(size_t __which)
233  { return _M_bin[__which]; }
234 
235  void
236  _M_adjust_freelist(const _Bin_record&, _Block_record*, size_t)
237  { }
238 
239  explicit __pool()
240  : _M_bin(0), _M_bin_size(1) { }
241 
242  explicit __pool(const __pool_base::_Tune& __tune)
243  : __pool_base(__tune), _M_bin(0), _M_bin_size(1) { }
244 
245  private:
246  // An "array" of bin_records each of which represents a specific
247  // power of 2 size. Memory to this "array" is allocated in
248  // _M_initialize().
249  _Bin_record* _M_bin;
250 
251  // Actual value calculated in _M_initialize().
252  size_t _M_bin_size;
253 
254  void
255  _M_initialize();
256  };
257 
258 #ifdef __GTHREADS
259  /// Specialization for thread enabled, via gthreads.h.
260  template<>
261  class __pool<true> : public __pool_base
262  {
263  public:
264  // Each requesting thread is assigned an id ranging from 1 to
265  // _S_max_threads. Thread id 0 is used as a global memory pool.
266  // In order to get constant performance on the thread assignment
267  // routine, we keep a list of free ids. When a thread first
268  // requests memory we remove the first record in this list and
269  // stores the address in a __gthread_key. When initializing the
270  // __gthread_key we specify a destructor. When this destructor
271  // (i.e. the thread dies) is called, we return the thread id to
272  // the front of this list.
273  struct _Thread_record
274  {
275  // Points to next free thread id record. NULL if last record in list.
276  _Thread_record* _M_next;
277 
278  // Thread id ranging from 1 to _S_max_threads.
279  size_t _M_id;
280  };
281 
282  union _Block_record
283  {
284  // Points to the block_record of the next free block.
285  _Block_record* _M_next;
286 
287  // The thread id of the thread which has requested this block.
288  size_t _M_thread_id;
289  };
290 
291  struct _Bin_record
292  {
293  // An "array" of pointers to the first free block for each
294  // thread id. Memory to this "array" is allocated in
295  // _S_initialize() for _S_max_threads + global pool 0.
296  _Block_record** _M_first;
297 
298  // A list of the initial addresses of all allocated blocks.
299  _Block_address* _M_address;
300 
301  // An "array" of counters used to keep track of the amount of
302  // blocks that are on the freelist/used for each thread id.
303  // - Note that the second part of the allocated _M_used "array"
304  // actually hosts (atomic) counters of reclaimed blocks: in
305  // _M_reserve_block and in _M_reclaim_block those numbers are
306  // subtracted from the first ones to obtain the actual size
307  // of the "working set" of the given thread.
308  // - Memory to these "arrays" is allocated in _S_initialize()
309  // for _S_max_threads + global pool 0.
310  size_t* _M_free;
311  size_t* _M_used;
312 
313  // Each bin has its own mutex which is used to ensure data
314  // integrity while changing "ownership" on a block. The mutex
315  // is initialized in _S_initialize().
316  __gthread_mutex_t* _M_mutex;
317  };
318 
319  // XXX GLIBCXX_ABI Deprecated
320  void
321  _M_initialize(__destroy_handler);
322 
323  void
324  _M_initialize_once()
325  {
326  if (__builtin_expect(_M_init == false, false))
327  _M_initialize();
328  }
329 
330  void
331  _M_destroy() throw();
332 
333  char*
334  _M_reserve_block(size_t __bytes, const size_t __thread_id);
335 
336  void
337  _M_reclaim_block(char* __p, size_t __bytes) throw ();
338 
339  const _Bin_record&
340  _M_get_bin(size_t __which)
341  { return _M_bin[__which]; }
342 
343  void
344  _M_adjust_freelist(const _Bin_record& __bin, _Block_record* __block,
345  size_t __thread_id)
346  {
347  if (__gthread_active_p())
348  {
349  __block->_M_thread_id = __thread_id;
350  --__bin._M_free[__thread_id];
351  ++__bin._M_used[__thread_id];
352  }
353  }
354 
355  // XXX GLIBCXX_ABI Deprecated
356  _GLIBCXX_CONST void
357  _M_destroy_thread_key(void*) throw ();
358 
359  size_t
360  _M_get_thread_id();
361 
362  explicit __pool()
363  : _M_bin(0), _M_bin_size(1), _M_thread_freelist(0)
364  { }
365 
366  explicit __pool(const __pool_base::_Tune& __tune)
367  : __pool_base(__tune), _M_bin(0), _M_bin_size(1),
368  _M_thread_freelist(0)
369  { }
370 
371  private:
372  // An "array" of bin_records each of which represents a specific
373  // power of 2 size. Memory to this "array" is allocated in
374  // _M_initialize().
375  _Bin_record* _M_bin;
376 
377  // Actual value calculated in _M_initialize().
378  size_t _M_bin_size;
379 
380  _Thread_record* _M_thread_freelist;
381  void* _M_thread_freelist_initial;
382 
383  void
384  _M_initialize();
385  };
386 #endif
387 
388  template<template <bool> class _PoolTp, bool _Thread>
389  struct __common_pool
390  {
391  typedef _PoolTp<_Thread> pool_type;
392 
393  static pool_type&
394  _S_get_pool()
395  {
396  static pool_type _S_pool;
397  return _S_pool;
398  }
399  };
400 
401  template<template <bool> class _PoolTp, bool _Thread>
402  struct __common_pool_base;
403 
404  template<template <bool> class _PoolTp>
405  struct __common_pool_base<_PoolTp, false>
406  : public __common_pool<_PoolTp, false>
407  {
408  using __common_pool<_PoolTp, false>::_S_get_pool;
409 
410  static void
411  _S_initialize_once()
412  {
413  static bool __init;
414  if (__builtin_expect(__init == false, false))
415  {
416  _S_get_pool()._M_initialize_once();
417  __init = true;
418  }
419  }
420  };
421 
422 #ifdef __GTHREADS
423  template<template <bool> class _PoolTp>
424  struct __common_pool_base<_PoolTp, true>
425  : public __common_pool<_PoolTp, true>
426  {
427  using __common_pool<_PoolTp, true>::_S_get_pool;
428 
429  static void
430  _S_initialize()
431  { _S_get_pool()._M_initialize_once(); }
432 
433  static void
434  _S_initialize_once()
435  {
436  static bool __init;
437  if (__builtin_expect(__init == false, false))
438  {
439  if (__gthread_active_p())
440  {
441  // On some platforms, __gthread_once_t is an aggregate.
442  static __gthread_once_t __once = __GTHREAD_ONCE_INIT;
443  __gthread_once(&__once, _S_initialize);
444  }
445 
446  // Double check initialization. May be necessary on some
447  // systems for proper construction when not compiling with
448  // thread flags.
449  _S_get_pool()._M_initialize_once();
450  __init = true;
451  }
452  }
453  };
454 #endif
455 
456  /// Policy for shared __pool objects.
457  template<template <bool> class _PoolTp, bool _Thread>
458  struct __common_pool_policy : public __common_pool_base<_PoolTp, _Thread>
459  {
460  template<typename _Tp1, template <bool> class _PoolTp1 = _PoolTp,
461  bool _Thread1 = _Thread>
462  struct _M_rebind
463  { typedef __common_pool_policy<_PoolTp1, _Thread1> other; };
464 
465  using __common_pool_base<_PoolTp, _Thread>::_S_get_pool;
466  using __common_pool_base<_PoolTp, _Thread>::_S_initialize_once;
467  };
468 
469 
470  template<typename _Tp, template <bool> class _PoolTp, bool _Thread>
471  struct __per_type_pool
472  {
473  typedef _Tp value_type;
474  typedef _PoolTp<_Thread> pool_type;
475 
476  static pool_type&
477  _S_get_pool()
478  {
479  // Sane defaults for the _PoolTp.
480  typedef typename pool_type::_Block_record _Block_record;
481  const static size_t __a = (__alignof__(_Tp) >= sizeof(_Block_record)
482  ? __alignof__(_Tp) : sizeof(_Block_record));
483 
484  typedef typename __pool_base::_Tune _Tune;
485  static _Tune _S_tune(__a, sizeof(_Tp) * 64,
486  sizeof(_Tp) * 2 >= __a ? sizeof(_Tp) * 2 : __a,
487  sizeof(_Tp) * size_t(_Tune::_S_chunk_size),
488  _Tune::_S_max_threads,
489  _Tune::_S_freelist_headroom,
490  std::getenv("GLIBCXX_FORCE_NEW") ? true : false);
491  static pool_type _S_pool(_S_tune);
492  return _S_pool;
493  }
494  };
495 
496  template<typename _Tp, template <bool> class _PoolTp, bool _Thread>
497  struct __per_type_pool_base;
498 
499  template<typename _Tp, template <bool> class _PoolTp>
500  struct __per_type_pool_base<_Tp, _PoolTp, false>
501  : public __per_type_pool<_Tp, _PoolTp, false>
502  {
503  using __per_type_pool<_Tp, _PoolTp, false>::_S_get_pool;
504 
505  static void
506  _S_initialize_once()
507  {
508  static bool __init;
509  if (__builtin_expect(__init == false, false))
510  {
511  _S_get_pool()._M_initialize_once();
512  __init = true;
513  }
514  }
515  };
516 
517  #ifdef __GTHREADS
518  template<typename _Tp, template <bool> class _PoolTp>
519  struct __per_type_pool_base<_Tp, _PoolTp, true>
520  : public __per_type_pool<_Tp, _PoolTp, true>
521  {
522  using __per_type_pool<_Tp, _PoolTp, true>::_S_get_pool;
523 
524  static void
525  _S_initialize()
526  { _S_get_pool()._M_initialize_once(); }
527 
528  static void
529  _S_initialize_once()
530  {
531  static bool __init;
532  if (__builtin_expect(__init == false, false))
533  {
534  if (__gthread_active_p())
535  {
536  // On some platforms, __gthread_once_t is an aggregate.
537  static __gthread_once_t __once = __GTHREAD_ONCE_INIT;
538  __gthread_once(&__once, _S_initialize);
539  }
540 
541  // Double check initialization. May be necessary on some
542  // systems for proper construction when not compiling with
543  // thread flags.
544  _S_get_pool()._M_initialize_once();
545  __init = true;
546  }
547  }
548  };
549 #endif
550 
551  /// Policy for individual __pool objects.
552  template<typename _Tp, template <bool> class _PoolTp, bool _Thread>
554  : public __per_type_pool_base<_Tp, _PoolTp, _Thread>
555  {
556  template<typename _Tp1, template <bool> class _PoolTp1 = _PoolTp,
557  bool _Thread1 = _Thread>
558  struct _M_rebind
560 
561  using __per_type_pool_base<_Tp, _PoolTp, _Thread>::_S_get_pool;
562  using __per_type_pool_base<_Tp, _PoolTp, _Thread>::_S_initialize_once;
563  };
564 
565 
566  /// Base class for _Tp dependent member functions.
567  template<typename _Tp>
569  {
570  public:
571  typedef size_t size_type;
572  typedef ptrdiff_t difference_type;
573  typedef _Tp* pointer;
574  typedef const _Tp* const_pointer;
575  typedef _Tp& reference;
576  typedef const _Tp& const_reference;
577  typedef _Tp value_type;
578 
579  pointer
580  address(reference __x) const _GLIBCXX_NOEXCEPT
581  { return std::__addressof(__x); }
582 
583  const_pointer
584  address(const_reference __x) const _GLIBCXX_NOEXCEPT
585  { return std::__addressof(__x); }
586 
587  size_type
588  max_size() const _GLIBCXX_USE_NOEXCEPT
589  { return size_t(-1) / sizeof(_Tp); }
590 
591 #ifdef __GXX_EXPERIMENTAL_CXX0X__
592  template<typename _Up, typename... _Args>
593  void
594  construct(_Up* __p, _Args&&... __args)
595  { ::new((void *)__p) _Up(std::forward<_Args>(__args)...); }
596 
597  template<typename _Up>
598  void
599  destroy(_Up* __p) { __p->~_Up(); }
600 #else
601  // _GLIBCXX_RESOLVE_LIB_DEFECTS
602  // 402. wrong new expression in [some_] allocator::construct
603  void
604  construct(pointer __p, const _Tp& __val)
605  { ::new((void *)__p) _Tp(__val); }
606 
607  void
608  destroy(pointer __p) { __p->~_Tp(); }
609 #endif
610  };
611 
612 #ifdef __GTHREADS
613 #define __thread_default true
614 #else
615 #define __thread_default false
616 #endif
617 
618  /**
619  * @brief This is a fixed size (power of 2) allocator which - when
620  * compiled with thread support - will maintain one freelist per
621  * size per thread plus a @a global one. Steps are taken to limit
622  * the per thread freelist sizes (by returning excess back to
623  * the @a global list).
624  * @ingroup allocators
625  *
626  * Further details:
627  * http://gcc.gnu.org/onlinedocs/libstdc++/manual/bk01pt12ch32.html
628  */
629  template<typename _Tp,
631  class __mt_alloc : public __mt_alloc_base<_Tp>
632  {
633  public:
634  typedef size_t size_type;
635  typedef ptrdiff_t difference_type;
636  typedef _Tp* pointer;
637  typedef const _Tp* const_pointer;
638  typedef _Tp& reference;
639  typedef const _Tp& const_reference;
640  typedef _Tp value_type;
641  typedef _Poolp __policy_type;
642  typedef typename _Poolp::pool_type __pool_type;
643 
644  template<typename _Tp1, typename _Poolp1 = _Poolp>
645  struct rebind
646  {
647  typedef typename _Poolp1::template _M_rebind<_Tp1>::other pol_type;
648  typedef __mt_alloc<_Tp1, pol_type> other;
649  };
650 
651  __mt_alloc() _GLIBCXX_USE_NOEXCEPT { }
652 
653  __mt_alloc(const __mt_alloc&) _GLIBCXX_USE_NOEXCEPT { }
654 
655  template<typename _Tp1, typename _Poolp1>
656  __mt_alloc(const __mt_alloc<_Tp1, _Poolp1>&) _GLIBCXX_USE_NOEXCEPT { }
657 
658  ~__mt_alloc() _GLIBCXX_USE_NOEXCEPT { }
659 
660  pointer
661  allocate(size_type __n, const void* = 0);
662 
663  void
664  deallocate(pointer __p, size_type __n);
665 
666  const __pool_base::_Tune
667  _M_get_options()
668  {
669  // Return a copy, not a reference, for external consumption.
670  return __policy_type::_S_get_pool()._M_get_options();
671  }
672 
673  void
674  _M_set_options(__pool_base::_Tune __t)
675  { __policy_type::_S_get_pool()._M_set_options(__t); }
676  };
677 
678  template<typename _Tp, typename _Poolp>
679  typename __mt_alloc<_Tp, _Poolp>::pointer
681  allocate(size_type __n, const void*)
682  {
683  if (__n > this->max_size())
684  std::__throw_bad_alloc();
685 
686  __policy_type::_S_initialize_once();
687 
688  // Requests larger than _M_max_bytes are handled by operator
689  // new/delete directly.
690  __pool_type& __pool = __policy_type::_S_get_pool();
691  const size_t __bytes = __n * sizeof(_Tp);
692  if (__pool._M_check_threshold(__bytes))
693  {
694  void* __ret = ::operator new(__bytes);
695  return static_cast<_Tp*>(__ret);
696  }
697 
698  // Round up to power of 2 and figure out which bin to use.
699  const size_t __which = __pool._M_get_binmap(__bytes);
700  const size_t __thread_id = __pool._M_get_thread_id();
701 
702  // Find out if we have blocks on our freelist. If so, go ahead
703  // and use them directly without having to lock anything.
704  char* __c;
705  typedef typename __pool_type::_Bin_record _Bin_record;
706  const _Bin_record& __bin = __pool._M_get_bin(__which);
707  if (__bin._M_first[__thread_id])
708  {
709  // Already reserved.
710  typedef typename __pool_type::_Block_record _Block_record;
711  _Block_record* __block = __bin._M_first[__thread_id];
712  __bin._M_first[__thread_id] = __block->_M_next;
713 
714  __pool._M_adjust_freelist(__bin, __block, __thread_id);
715  __c = reinterpret_cast<char*>(__block) + __pool._M_get_align();
716  }
717  else
718  {
719  // Null, reserve.
720  __c = __pool._M_reserve_block(__bytes, __thread_id);
721  }
722  return static_cast<_Tp*>(static_cast<void*>(__c));
723  }
724 
725  template<typename _Tp, typename _Poolp>
726  void
727  __mt_alloc<_Tp, _Poolp>::
728  deallocate(pointer __p, size_type __n)
729  {
730  if (__builtin_expect(__p != 0, true))
731  {
732  // Requests larger than _M_max_bytes are handled by
733  // operators new/delete directly.
734  __pool_type& __pool = __policy_type::_S_get_pool();
735  const size_t __bytes = __n * sizeof(_Tp);
736  if (__pool._M_check_threshold(__bytes))
737  ::operator delete(__p);
738  else
739  __pool._M_reclaim_block(reinterpret_cast<char*>(__p), __bytes);
740  }
741  }
742 
743  template<typename _Tp, typename _Poolp>
744  inline bool
745  operator==(const __mt_alloc<_Tp, _Poolp>&, const __mt_alloc<_Tp, _Poolp>&)
746  { return true; }
747 
748  template<typename _Tp, typename _Poolp>
749  inline bool
750  operator!=(const __mt_alloc<_Tp, _Poolp>&, const __mt_alloc<_Tp, _Poolp>&)
751  { return false; }
752 
753 #undef __thread_default
754 
755 _GLIBCXX_END_NAMESPACE_VERSION
756 } // namespace
757 
758 #endif