mt_allocator.h revision 132720
1// MT-optimized allocator -*- C++ -*- 2 3// Copyright (C) 2003, 2004 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 2, 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// You should have received a copy of the GNU General Public License along 17// with this library; see the file COPYING. If not, write to the Free 18// Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, 19// USA. 20 21// As a special exception, you may use this file as part of a free software 22// library without restriction. Specifically, if other files instantiate 23// templates or use macros or inline functions from this file, or you compile 24// this file and link it with other files to produce an executable, this 25// file does not by itself cause the resulting executable to be covered by 26// the GNU General Public License. This exception does not however 27// invalidate any other reasons why the executable file might be covered by 28// the GNU General Public License. 29 30/** @file ext/mt_allocator.h 31 * This file is a GNU extension to the Standard C++ Library. 32 * You should only include this header if you are using GCC 3 or later. 33 */ 34 35#ifndef _MT_ALLOCATOR_H 36#define _MT_ALLOCATOR_H 1 37 38#include <new> 39#include <cstdlib> 40#include <bits/functexcept.h> 41#include <bits/gthr.h> 42#include <bits/atomicity.h> 43 44namespace __gnu_cxx 45{ 46 /** 47 * This is a fixed size (power of 2) allocator which - when 48 * compiled with thread support - will maintain one freelist per 49 * size per thread plus a "global" one. Steps are taken to limit 50 * the per thread freelist sizes (by returning excess back to 51 * "global"). 52 * 53 * Further details: 54 * http://gcc.gnu.org/onlinedocs/libstdc++/ext/mt_allocator.html 55 */ 56 template<typename _Tp> 57 class __mt_alloc 58 { 59 public: 60 typedef size_t size_type; 61 typedef ptrdiff_t difference_type; 62 typedef _Tp* pointer; 63 typedef const _Tp* const_pointer; 64 typedef _Tp& reference; 65 typedef const _Tp& const_reference; 66 typedef _Tp value_type; 67 68 template<typename _Tp1> 69 struct rebind 70 { typedef __mt_alloc<_Tp1> other; }; 71 72 __mt_alloc() throw() 73 { 74 // XXX 75 } 76 77 __mt_alloc(const __mt_alloc&) throw() 78 { 79 // XXX 80 } 81 82 template<typename _Tp1> 83 __mt_alloc(const __mt_alloc<_Tp1>& obj) throw() 84 { 85 // XXX 86 } 87 88 ~__mt_alloc() throw() { } 89 90 pointer 91 address(reference __x) const 92 { return &__x; } 93 94 const_pointer 95 address(const_reference __x) const 96 { return &__x; } 97 98 size_type 99 max_size() const throw() 100 { return size_t(-1) / sizeof(_Tp); } 101 102 // _GLIBCXX_RESOLVE_LIB_DEFECTS 103 // 402. wrong new expression in [some_] allocator::construct 104 void 105 construct(pointer __p, const _Tp& __val) 106 { ::new(__p) _Tp(__val); } 107 108 void 109 destroy(pointer __p) { __p->~_Tp(); } 110 111 pointer 112 allocate(size_type __n, const void* = 0); 113 114 void 115 deallocate(pointer __p, size_type __n); 116 117 // Variables used to configure the behavior of the allocator, 118 // assigned and explained in detail below. 119 struct _Tune 120 { 121 // Alignment needed. 122 // NB: In any case must be >= sizeof(_Block_record), that 123 // is 4 on 32 bit machines and 8 on 64 bit machines. 124 size_t _M_align; 125 126 // Allocation requests (after round-up to power of 2) below 127 // this value will be handled by the allocator. A raw new/ 128 // call will be used for requests larger than this value. 129 size_t _M_max_bytes; 130 131 // Size in bytes of the smallest bin. 132 // NB: Must be a power of 2 and >= _M_align. 133 size_t _M_min_bin; 134 135 // In order to avoid fragmenting and minimize the number of 136 // new() calls we always request new memory using this 137 // value. Based on previous discussions on the libstdc++ 138 // mailing list we have choosen the value below. 139 // See http://gcc.gnu.org/ml/libstdc++/2001-07/msg00077.html 140 size_t _M_chunk_size; 141 142 // The maximum number of supported threads. Our Linux 2.4.18 143 // reports 4070 in /proc/sys/kernel/threads-max 144 size_t _M_max_threads; 145 146 // Each time a deallocation occurs in a threaded application 147 // we make sure that there are no more than 148 // _M_freelist_headroom % of used memory on the freelist. If 149 // the number of additional records is more than 150 // _M_freelist_headroom % of the freelist, we move these 151 // records back to the global pool. 152 size_t _M_freelist_headroom; 153 154 // Set to true forces all allocations to use new(). 155 bool _M_force_new; 156 157 explicit 158 _Tune() 159 : _M_align(8), _M_max_bytes(128), _M_min_bin(8), 160 _M_chunk_size(4096 - 4 * sizeof(void*)), 161 _M_max_threads(4096), _M_freelist_headroom(10), 162 _M_force_new(getenv("GLIBCXX_FORCE_NEW") ? true : false) 163 { } 164 165 explicit 166 _Tune(size_t __align, size_t __maxb, size_t __minbin, 167 size_t __chunk, size_t __maxthreads, size_t __headroom, 168 bool __force) 169 : _M_align(__align), _M_max_bytes(__maxb), _M_min_bin(__minbin), 170 _M_chunk_size(__chunk), _M_max_threads(__maxthreads), 171 _M_freelist_headroom(__headroom), _M_force_new(__force) 172 { } 173 }; 174 175 private: 176 // We need to create the initial lists and set up some variables 177 // before we can answer to the first request for memory. 178#ifdef __GTHREADS 179 static __gthread_once_t _S_once; 180#endif 181 static bool _S_init; 182 183 static void 184 _S_initialize(); 185 186 // Configuration options. 187 static _Tune _S_options; 188 189 static const _Tune 190 _S_get_options() 191 { return _S_options; } 192 193 static void 194 _S_set_options(_Tune __t) 195 { 196 if (!_S_init) 197 _S_options = __t; 198 } 199 200 // Using short int as type for the binmap implies we are never 201 // caching blocks larger than 65535 with this allocator 202 typedef unsigned short int _Binmap_type; 203 static _Binmap_type* _S_binmap; 204 205 // Each requesting thread is assigned an id ranging from 1 to 206 // _S_max_threads. Thread id 0 is used as a global memory pool. 207 // In order to get constant performance on the thread assignment 208 // routine, we keep a list of free ids. When a thread first 209 // requests memory we remove the first record in this list and 210 // stores the address in a __gthread_key. When initializing the 211 // __gthread_key we specify a destructor. When this destructor 212 // (i.e. the thread dies) is called, we return the thread id to 213 // the front of this list. 214#ifdef __GTHREADS 215 struct _Thread_record 216 { 217 // Points to next free thread id record. NULL if last record in list. 218 _Thread_record* volatile _M_next; 219 220 // Thread id ranging from 1 to _S_max_threads. 221 size_t _M_id; 222 }; 223 224 static _Thread_record* volatile _S_thread_freelist_first; 225 static __gthread_mutex_t _S_thread_freelist_mutex; 226 static __gthread_key_t _S_thread_key; 227 228 static void 229 _S_destroy_thread_key(void* __freelist_pos); 230#endif 231 232 static size_t 233 _S_get_thread_id(); 234 235 union _Block_record 236 { 237 // Points to the block_record of the next free block. 238 _Block_record* volatile _M_next; 239 240#ifdef __GTHREADS 241 // The thread id of the thread which has requested this block. 242 size_t _M_thread_id; 243#endif 244 }; 245 246 struct _Bin_record 247 { 248 // An "array" of pointers to the first free block for each 249 // thread id. Memory to this "array" is allocated in _S_initialize() 250 // for _S_max_threads + global pool 0. 251 _Block_record** volatile _M_first; 252 253#ifdef __GTHREADS 254 // An "array" of counters used to keep track of the amount of 255 // blocks that are on the freelist/used for each thread id. 256 // Memory to these "arrays" is allocated in _S_initialize() for 257 // _S_max_threads + global pool 0. 258 size_t* volatile _M_free; 259 size_t* volatile _M_used; 260 261 // Each bin has its own mutex which is used to ensure data 262 // integrity while changing "ownership" on a block. The mutex 263 // is initialized in _S_initialize(). 264 __gthread_mutex_t* _M_mutex; 265#endif 266 }; 267 268 // An "array" of bin_records each of which represents a specific 269 // power of 2 size. Memory to this "array" is allocated in 270 // _S_initialize(). 271 static _Bin_record* volatile _S_bin; 272 273 // Actual value calculated in _S_initialize(). 274 static size_t _S_bin_size; 275 }; 276 277 template<typename _Tp> 278 typename __mt_alloc<_Tp>::pointer 279 __mt_alloc<_Tp>:: 280 allocate(size_type __n, const void*) 281 { 282 // Although the test in __gthread_once() would suffice, we wrap 283 // test of the once condition in our own unlocked check. This 284 // saves one function call to pthread_once() (which itself only 285 // tests for the once value unlocked anyway and immediately 286 // returns if set) 287 if (!_S_init) 288 { 289#ifdef __GTHREADS 290 if (__gthread_active_p()) 291 __gthread_once(&_S_once, _S_initialize); 292#endif 293 if (!_S_init) 294 _S_initialize(); 295 } 296 297 // Requests larger than _M_max_bytes are handled by new/delete 298 // directly. 299 const size_t __bytes = __n * sizeof(_Tp); 300 if (__bytes > _S_options._M_max_bytes || _S_options._M_force_new) 301 { 302 void* __ret = ::operator new(__bytes); 303 return static_cast<_Tp*>(__ret); 304 } 305 306 // Round up to power of 2 and figure out which bin to use. 307 const size_t __which = _S_binmap[__bytes]; 308 const size_t __thread_id = _S_get_thread_id(); 309 310 // Find out if we have blocks on our freelist. If so, go ahead 311 // and use them directly without having to lock anything. 312 const _Bin_record& __bin = _S_bin[__which]; 313 _Block_record* __block = NULL; 314 if (__bin._M_first[__thread_id] == NULL) 315 { 316 // NB: For alignment reasons, we can't use the first _M_align 317 // bytes, even when sizeof(_Block_record) < _M_align. 318 const size_t __bin_size = ((_S_options._M_min_bin << __which) 319 + _S_options._M_align); 320 size_t __block_count = _S_options._M_chunk_size / __bin_size; 321 322 // Are we using threads? 323 // - Yes, check if there are free blocks on the global 324 // list. If so, grab up to __block_count blocks in one 325 // lock and change ownership. If the global list is 326 // empty, we allocate a new chunk and add those blocks 327 // directly to our own freelist (with us as owner). 328 // - No, all operations are made directly to global pool 0 329 // no need to lock or change ownership but check for free 330 // blocks on global list (and if not add new ones) and 331 // get the first one. 332#ifdef __GTHREADS 333 if (__gthread_active_p()) 334 { 335 __gthread_mutex_lock(__bin._M_mutex); 336 if (__bin._M_first[0] == NULL) 337 { 338 // No need to hold the lock when we are adding a 339 // whole chunk to our own list. 340 __gthread_mutex_unlock(__bin._M_mutex); 341 342 void* __v = ::operator new(_S_options._M_chunk_size); 343 __bin._M_first[__thread_id] = static_cast<_Block_record*>(__v); 344 __bin._M_free[__thread_id] = __block_count; 345 346 --__block_count; 347 __block = __bin._M_first[__thread_id]; 348 while (__block_count-- > 0) 349 { 350 char* __c = reinterpret_cast<char*>(__block) + __bin_size; 351 __block->_M_next = reinterpret_cast<_Block_record*>(__c); 352 __block = __block->_M_next; 353 } 354 __block->_M_next = NULL; 355 } 356 else 357 { 358 // Is the number of required blocks greater than or 359 // equal to the number that can be provided by the 360 // global free list? 361 __bin._M_first[__thread_id] = __bin._M_first[0]; 362 if (__block_count >= __bin._M_free[0]) 363 { 364 __bin._M_free[__thread_id] = __bin._M_free[0]; 365 __bin._M_free[0] = 0; 366 __bin._M_first[0] = NULL; 367 } 368 else 369 { 370 __bin._M_free[__thread_id] = __block_count; 371 __bin._M_free[0] -= __block_count; 372 --__block_count; 373 __block = __bin._M_first[0]; 374 while (__block_count-- > 0) 375 __block = __block->_M_next; 376 __bin._M_first[0] = __block->_M_next; 377 __block->_M_next = NULL; 378 } 379 __gthread_mutex_unlock(__bin._M_mutex); 380 } 381 } 382 else 383#endif 384 { 385 void* __v = ::operator new(_S_options._M_chunk_size); 386 __bin._M_first[0] = static_cast<_Block_record*>(__v); 387 388 --__block_count; 389 __block = __bin._M_first[0]; 390 while (__block_count-- > 0) 391 { 392 char* __c = reinterpret_cast<char*>(__block) + __bin_size; 393 __block->_M_next = reinterpret_cast<_Block_record*>(__c); 394 __block = __block->_M_next; 395 } 396 __block->_M_next = NULL; 397 } 398 } 399 400 __block = __bin._M_first[__thread_id]; 401 __bin._M_first[__thread_id] = __bin._M_first[__thread_id]->_M_next; 402#ifdef __GTHREADS 403 if (__gthread_active_p()) 404 { 405 __block->_M_thread_id = __thread_id; 406 --__bin._M_free[__thread_id]; 407 ++__bin._M_used[__thread_id]; 408 } 409#endif 410 411 char* __c = reinterpret_cast<char*>(__block) + _S_options._M_align; 412 return static_cast<_Tp*>(static_cast<void*>(__c)); 413 } 414 415 template<typename _Tp> 416 void 417 __mt_alloc<_Tp>:: 418 deallocate(pointer __p, size_type __n) 419 { 420 // Requests larger than _M_max_bytes are handled by operators 421 // new/delete directly. 422 const size_t __bytes = __n * sizeof(_Tp); 423 if (__bytes > _S_options._M_max_bytes || _S_options._M_force_new) 424 { 425 ::operator delete(__p); 426 return; 427 } 428 429 // Round up to power of 2 and figure out which bin to use. 430 const size_t __which = _S_binmap[__bytes]; 431 const _Bin_record& __bin = _S_bin[__which]; 432 433 char* __c = reinterpret_cast<char*>(__p) - _S_options._M_align; 434 _Block_record* __block = reinterpret_cast<_Block_record*>(__c); 435 436#ifdef __GTHREADS 437 if (__gthread_active_p()) 438 { 439 // Calculate the number of records to remove from our freelist: 440 // in order to avoid too much contention we wait until the 441 // number of records is "high enough". 442 const size_t __thread_id = _S_get_thread_id(); 443 444 long __remove = ((__bin._M_free[__thread_id] 445 * _S_options._M_freelist_headroom) 446 - __bin._M_used[__thread_id]); 447 if (__remove > static_cast<long>(100 * (_S_bin_size - __which) 448 * _S_options._M_freelist_headroom) 449 && __remove > static_cast<long>(__bin._M_free[__thread_id])) 450 { 451 _Block_record* __tmp = __bin._M_first[__thread_id]; 452 _Block_record* __first = __tmp; 453 __remove /= _S_options._M_freelist_headroom; 454 const long __removed = __remove; 455 --__remove; 456 while (__remove-- > 0) 457 __tmp = __tmp->_M_next; 458 __bin._M_first[__thread_id] = __tmp->_M_next; 459 __bin._M_free[__thread_id] -= __removed; 460 461 __gthread_mutex_lock(__bin._M_mutex); 462 __tmp->_M_next = __bin._M_first[0]; 463 __bin._M_first[0] = __first; 464 __bin._M_free[0] += __removed; 465 __gthread_mutex_unlock(__bin._M_mutex); 466 } 467 468 // Return this block to our list and update counters and 469 // owner id as needed. 470 --__bin._M_used[__block->_M_thread_id]; 471 472 __block->_M_next = __bin._M_first[__thread_id]; 473 __bin._M_first[__thread_id] = __block; 474 475 ++__bin._M_free[__thread_id]; 476 } 477 else 478#endif 479 { 480 // Single threaded application - return to global pool. 481 __block->_M_next = __bin._M_first[0]; 482 __bin._M_first[0] = __block; 483 } 484 } 485 486 template<typename _Tp> 487 void 488 __mt_alloc<_Tp>:: 489 _S_initialize() 490 { 491 // This method is called on the first allocation (when _S_init is still 492 // false) to create the bins. 493 494 // Ensure that the static initialization of _S_options has 495 // happened. This depends on (a) _M_align == 0 being an invalid 496 // value that is only present at startup, and (b) the real 497 // static initialization that happens later not actually 498 // changing anything. 499 if (_S_options._M_align == 0) 500 new (&_S_options) _Tune; 501 502 // _M_force_new must not change after the first allocate(), 503 // which in turn calls this method, so if it's false, it's false 504 // forever and we don't need to return here ever again. 505 if (_S_options._M_force_new) 506 { 507 _S_init = true; 508 return; 509 } 510 511 // Calculate the number of bins required based on _M_max_bytes. 512 // _S_bin_size is statically-initialized to one. 513 size_t __bin_size = _S_options._M_min_bin; 514 while (_S_options._M_max_bytes > __bin_size) 515 { 516 __bin_size <<= 1; 517 ++_S_bin_size; 518 } 519 520 // Setup the bin map for quick lookup of the relevant bin. 521 const size_t __j = (_S_options._M_max_bytes + 1) * sizeof(_Binmap_type); 522 _S_binmap = static_cast<_Binmap_type*>(::operator new(__j)); 523 524 _Binmap_type* __bp = _S_binmap; 525 _Binmap_type __bin_max = _S_options._M_min_bin; 526 _Binmap_type __bint = 0; 527 for (_Binmap_type __ct = 0; __ct <= _S_options._M_max_bytes; ++__ct) 528 { 529 if (__ct > __bin_max) 530 { 531 __bin_max <<= 1; 532 ++__bint; 533 } 534 *__bp++ = __bint; 535 } 536 537 // Initialize _S_bin and its members. 538 void* __v = ::operator new(sizeof(_Bin_record) * _S_bin_size); 539 _S_bin = static_cast<_Bin_record*>(__v); 540 541 // If __gthread_active_p() create and initialize the list of 542 // free thread ids. Single threaded applications use thread id 0 543 // directly and have no need for this. 544#ifdef __GTHREADS 545 if (__gthread_active_p()) 546 { 547 const size_t __k = sizeof(_Thread_record) * _S_options._M_max_threads; 548 __v = ::operator new(__k); 549 _S_thread_freelist_first = static_cast<_Thread_record*>(__v); 550 551 // NOTE! The first assignable thread id is 1 since the 552 // global pool uses id 0 553 size_t __i; 554 for (__i = 1; __i < _S_options._M_max_threads; ++__i) 555 { 556 _Thread_record& __tr = _S_thread_freelist_first[__i - 1]; 557 __tr._M_next = &_S_thread_freelist_first[__i]; 558 __tr._M_id = __i; 559 } 560 561 // Set last record. 562 _S_thread_freelist_first[__i - 1]._M_next = NULL; 563 _S_thread_freelist_first[__i - 1]._M_id = __i; 564 565 // Make sure this is initialized. 566#ifndef __GTHREAD_MUTEX_INIT 567 __GTHREAD_MUTEX_INIT_FUNCTION(&_S_thread_freelist_mutex); 568#endif 569 // Initialize per thread key to hold pointer to 570 // _S_thread_freelist. 571 __gthread_key_create(&_S_thread_key, _S_destroy_thread_key); 572 573 const size_t __max_threads = _S_options._M_max_threads + 1; 574 for (size_t __n = 0; __n < _S_bin_size; ++__n) 575 { 576 _Bin_record& __bin = _S_bin[__n]; 577 __v = ::operator new(sizeof(_Block_record*) * __max_threads); 578 __bin._M_first = static_cast<_Block_record**>(__v); 579 580 __v = ::operator new(sizeof(size_t) * __max_threads); 581 __bin._M_free = static_cast<size_t*>(__v); 582 583 __v = ::operator new(sizeof(size_t) * __max_threads); 584 __bin._M_used = static_cast<size_t*>(__v); 585 586 __v = ::operator new(sizeof(__gthread_mutex_t)); 587 __bin._M_mutex = static_cast<__gthread_mutex_t*>(__v); 588 589#ifdef __GTHREAD_MUTEX_INIT 590 { 591 // Do not copy a POSIX/gthr mutex once in use. 592 __gthread_mutex_t __tmp = __GTHREAD_MUTEX_INIT; 593 *__bin._M_mutex = __tmp; 594 } 595#else 596 { __GTHREAD_MUTEX_INIT_FUNCTION(__bin._M_mutex); } 597#endif 598 599 for (size_t __threadn = 0; __threadn < __max_threads; 600 ++__threadn) 601 { 602 __bin._M_first[__threadn] = NULL; 603 __bin._M_free[__threadn] = 0; 604 __bin._M_used[__threadn] = 0; 605 } 606 } 607 } 608 else 609#endif 610 for (size_t __n = 0; __n < _S_bin_size; ++__n) 611 { 612 _Bin_record& __bin = _S_bin[__n]; 613 __v = ::operator new(sizeof(_Block_record*)); 614 __bin._M_first = static_cast<_Block_record**>(__v); 615 __bin._M_first[0] = NULL; 616 } 617 618 _S_init = true; 619 } 620 621 template<typename _Tp> 622 size_t 623 __mt_alloc<_Tp>:: 624 _S_get_thread_id() 625 { 626#ifdef __GTHREADS 627 // If we have thread support and it's active we check the thread 628 // key value and return its id or if it's not set we take the 629 // first record from _S_thread_freelist and sets the key and 630 // returns it's id. 631 if (__gthread_active_p()) 632 { 633 _Thread_record* __freelist_pos = 634 static_cast<_Thread_record*>(__gthread_getspecific(_S_thread_key)); 635 if (__freelist_pos == NULL) 636 { 637 // Since _S_options._M_max_threads must be larger than 638 // the theoretical max number of threads of the OS the 639 // list can never be empty. 640 __gthread_mutex_lock(&_S_thread_freelist_mutex); 641 __freelist_pos = _S_thread_freelist_first; 642 _S_thread_freelist_first = _S_thread_freelist_first->_M_next; 643 __gthread_mutex_unlock(&_S_thread_freelist_mutex); 644 645 __gthread_setspecific(_S_thread_key, 646 static_cast<void*>(__freelist_pos)); 647 } 648 return __freelist_pos->_M_id; 649 } 650#endif 651 // Otherwise (no thread support or inactive) all requests are 652 // served from the global pool 0. 653 return 0; 654 } 655 656#ifdef __GTHREADS 657 template<typename _Tp> 658 void 659 __mt_alloc<_Tp>:: 660 _S_destroy_thread_key(void* __freelist_pos) 661 { 662 // Return this thread id record to front of thread_freelist. 663 __gthread_mutex_lock(&_S_thread_freelist_mutex); 664 _Thread_record* __tr = static_cast<_Thread_record*>(__freelist_pos); 665 __tr->_M_next = _S_thread_freelist_first; 666 _S_thread_freelist_first = __tr; 667 __gthread_mutex_unlock(&_S_thread_freelist_mutex); 668 } 669#endif 670 671 template<typename _Tp> 672 inline bool 673 operator==(const __mt_alloc<_Tp>&, const __mt_alloc<_Tp>&) 674 { return true; } 675 676 template<typename _Tp> 677 inline bool 678 operator!=(const __mt_alloc<_Tp>&, const __mt_alloc<_Tp>&) 679 { return false; } 680 681 template<typename _Tp> 682 bool __mt_alloc<_Tp>::_S_init = false; 683 684 template<typename _Tp> 685 typename __mt_alloc<_Tp>::_Tune __mt_alloc<_Tp>::_S_options; 686 687 template<typename _Tp> 688 typename __mt_alloc<_Tp>::_Binmap_type* __mt_alloc<_Tp>::_S_binmap; 689 690 template<typename _Tp> 691 typename __mt_alloc<_Tp>::_Bin_record* volatile __mt_alloc<_Tp>::_S_bin; 692 693 template<typename _Tp> 694 size_t __mt_alloc<_Tp>::_S_bin_size = 1; 695 696 // Actual initialization in _S_initialize(). 697#ifdef __GTHREADS 698 template<typename _Tp> 699 __gthread_once_t __mt_alloc<_Tp>::_S_once = __GTHREAD_ONCE_INIT; 700 701 template<typename _Tp> 702 typename __mt_alloc<_Tp>::_Thread_record* 703 volatile __mt_alloc<_Tp>::_S_thread_freelist_first = NULL; 704 705 template<typename _Tp> 706 __gthread_key_t __mt_alloc<_Tp>::_S_thread_key; 707 708 template<typename _Tp> 709 __gthread_mutex_t 710#ifdef __GTHREAD_MUTEX_INIT 711 __mt_alloc<_Tp>::_S_thread_freelist_mutex = __GTHREAD_MUTEX_INIT; 712#else 713 __mt_alloc<_Tp>::_S_thread_freelist_mutex; 714#endif 715#endif 716} // namespace __gnu_cxx 717 718#endif 719