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The C and C++ Include Header Files
/usr/include/c++/13/ext/mt_allocator.h
$ cat -n /usr/include/c++/13/ext/mt_allocator.h 1 // MT-optimized allocator -*- C++ -*- 2 3 // Copyright (C) 2003-2023 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 /** @file ext/mt_allocator.h 26 * This file is a GNU extension to the Standard C++ Library. 27 */ 28 29 #ifndef _MT_ALLOCATOR_H 30 #define _MT_ALLOCATOR_H 1 31 32 #include <bits/requires_hosted.h> // getenv 33 34 #include <new> 35 #include <cstdlib> 36 #include <bits/functexcept.h> 37 #include <ext/atomicity.h> 38 #include <bits/move.h> 39 #if __cplusplus >= 201103L 40 #include <type_traits> 41 #endif 42 43 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default) 44 { 45 _GLIBCXX_BEGIN_NAMESPACE_VERSION 46 47 48 typedef void (*__destroy_handler)(void*); 49 50 /// Base class for pool object. 51 struct __pool_base 52 { 53 // Using short int as type for the binmap implies we are never 54 // caching blocks larger than 32768 with this allocator. 55 typedef unsigned short int _Binmap_type; 56 typedef std::size_t size_t; 57 58 // Variables used to configure the behavior of the allocator, 59 // assigned and explained in detail below. 60 struct _Tune 61 { 62 // Compile time constants for the default _Tune values. 63 enum { _S_align = 8 }; 64 enum { _S_max_bytes = 128 }; 65 enum { _S_min_bin = 8 }; 66 enum { _S_chunk_size = 4096 - 4 * sizeof(void*) }; 67 enum { _S_max_threads = 4096 }; 68 enum { _S_freelist_headroom = 10 }; 69 70 // Alignment needed. 71 // NB: In any case must be >= sizeof(_Block_record), that 72 // is 4 on 32 bit machines and 8 on 64 bit machines. 73 size_t _M_align; 74 75 // Allocation requests (after round-up to power of 2) below 76 // this value will be handled by the allocator. A raw new/ 77 // call will be used for requests larger than this value. 78 // NB: Must be much smaller than _M_chunk_size and in any 79 // case <= 32768. 80 size_t _M_max_bytes; 81 82 // Size in bytes of the smallest bin. 83 // NB: Must be a power of 2 and >= _M_align (and of course 84 // much smaller than _M_max_bytes). 85 size_t _M_min_bin; 86 87 // In order to avoid fragmenting and minimize the number of 88 // new() calls we always request new memory using this 89 // value. Based on previous discussions on the libstdc++ 90 // mailing list we have chosen the value below. 91 // See http://gcc.gnu.org/ml/libstdc++/2001-07/msg00077.html 92 // NB: At least one order of magnitude > _M_max_bytes. 93 size_t _M_chunk_size; 94 95 // The maximum number of supported threads. For 96 // single-threaded operation, use one. Maximum values will 97 // vary depending on details of the underlying system. (For 98 // instance, Linux 2.4.18 reports 4070 in 99 // /proc/sys/kernel/threads-max, while Linux 2.6.6 reports 100 // 65534) 101 size_t _M_max_threads; 102 103 // Each time a deallocation occurs in a threaded application 104 // we make sure that there are no more than 105 // _M_freelist_headroom % of used memory on the freelist. If 106 // the number of additional records is more than 107 // _M_freelist_headroom % of the freelist, we move these 108 // records back to the global pool. 109 size_t _M_freelist_headroom; 110 111 // Set to true forces all allocations to use new(). 112 bool _M_force_new; 113 114 explicit 115 _Tune() 116 : _M_align(_S_align), _M_max_bytes(_S_max_bytes), _M_min_bin(_S_min_bin), 117 _M_chunk_size(_S_chunk_size), _M_max_threads(_S_max_threads), 118 _M_freelist_headroom(_S_freelist_headroom), 119 _M_force_new(std::getenv("GLIBCXX_FORCE_NEW") ? true : false) 120 { } 121 122 explicit 123 _Tune(size_t __align, size_t __maxb, size_t __minbin, size_t __chunk, 124 size_t __maxthreads, size_t __headroom, bool __force) 125 : _M_align(__align), _M_max_bytes(__maxb), _M_min_bin(__minbin), 126 _M_chunk_size(__chunk), _M_max_threads(__maxthreads), 127 _M_freelist_headroom(__headroom), _M_force_new(__force) 128 { } 129 }; 130 131 struct _Block_address 132 { 133 void* _M_initial; 134 _Block_address* _M_next; 135 }; 136 137 const _Tune& 138 _M_get_options() const 139 { return _M_options; } 140 141 void 142 _M_set_options(_Tune __t) 143 { 144 if (!_M_init) 145 _M_options = __t; 146 } 147 148 bool 149 _M_check_threshold(size_t __bytes) 150 { return __bytes > _M_options._M_max_bytes || _M_options._M_force_new; } 151 152 size_t 153 _M_get_binmap(size_t __bytes) 154 { return _M_binmap[__bytes]; } 155 156 size_t 157 _M_get_align() 158 { return _M_options._M_align; } 159 160 explicit 161 __pool_base() 162 : _M_options(_Tune()), _M_binmap(0), _M_init(false) { } 163 164 explicit 165 __pool_base(const _Tune& __options) 166 : _M_options(__options), _M_binmap(0), _M_init(false) { } 167 168 private: 169 explicit 170 __pool_base(const __pool_base&); 171 172 __pool_base& 173 operator=(const __pool_base&); 174 175 protected: 176 // Configuration options. 177 _Tune _M_options; 178 179 _Binmap_type* _M_binmap; 180 181 // Configuration of the pool object via _M_options can happen 182 // after construction but before initialization. After 183 // initialization is complete, this variable is set to true. 184 bool _M_init; 185 }; 186 187 188 /** 189 * @brief Data describing the underlying memory pool, parameterized on 190 * threading support. 191 */ 192 template<bool _Thread> 193 class __pool; 194 195 /// Specialization for single thread. 196 template<> 197 class __pool<false> : public __pool_base 198 { 199 public: 200 union _Block_record 201 { 202 // Points to the block_record of the next free block. 203 _Block_record* _M_next; 204 }; 205 206 struct _Bin_record 207 { 208 // An "array" of pointers to the first free block. 209 _Block_record** _M_first; 210 211 // A list of the initial addresses of all allocated blocks. 212 _Block_address* _M_address; 213 }; 214 215 void 216 _M_initialize_once() 217 { 218 if (__builtin_expect(_M_init == false, false)) 219 _M_initialize(); 220 } 221 222 void 223 _M_destroy() throw(); 224 225 char* 226 _M_reserve_block(size_t __bytes, const size_t __thread_id); 227 228 void 229 _M_reclaim_block(char* __p, size_t __bytes) throw (); 230 231 size_t 232 _M_get_thread_id() { return 0; } 233 234 const _Bin_record& 235 _M_get_bin(size_t __which) 236 { return _M_bin[__which]; } 237 238 void 239 _M_adjust_freelist(const _Bin_record&, _Block_record*, size_t) 240 { } 241 242 explicit __pool() 243 : _M_bin(0), _M_bin_size(1) { } 244 245 explicit __pool(const __pool_base::_Tune& __tune) 246 : __pool_base(__tune), _M_bin(0), _M_bin_size(1) { } 247 248 private: 249 // An "array" of bin_records each of which represents a specific 250 // power of 2 size. Memory to this "array" is allocated in 251 // _M_initialize(). 252 _Bin_record* _M_bin; 253 254 // Actual value calculated in _M_initialize(). 255 size_t _M_bin_size; 256 257 void 258 _M_initialize(); 259 }; 260 261 #ifdef __GTHREADS 262 /// Specialization for thread enabled, via gthreads.h. 263 template<> 264 class __pool<true> : public __pool_base 265 { 266 public: 267 // Each requesting thread is assigned an id ranging from 1 to 268 // _S_max_threads. Thread id 0 is used as a global memory pool. 269 // In order to get constant performance on the thread assignment 270 // routine, we keep a list of free ids. When a thread first 271 // requests memory we remove the first record in this list and 272 // stores the address in a __gthread_key. When initializing the 273 // __gthread_key we specify a destructor. When this destructor 274 // (i.e. the thread dies) is called, we return the thread id to 275 // the front of this list. 276 struct _Thread_record 277 { 278 // Points to next free thread id record. NULL if last record in list. 279 _Thread_record* _M_next; 280 281 // Thread id ranging from 1 to _S_max_threads. 282 size_t _M_id; 283 }; 284 285 union _Block_record 286 { 287 // Points to the block_record of the next free block. 288 _Block_record* _M_next; 289 290 // The thread id of the thread which has requested this block. 291 size_t _M_thread_id; 292 }; 293 294 struct _Bin_record 295 { 296 // An "array" of pointers to the first free block for each 297 // thread id. Memory to this "array" is allocated in 298 // _S_initialize() for _S_max_threads + global pool 0. 299 _Block_record** _M_first; 300 301 // A list of the initial addresses of all allocated blocks. 302 _Block_address* _M_address; 303 304 // An "array" of counters used to keep track of the amount of 305 // blocks that are on the freelist/used for each thread id. 306 // - Note that the second part of the allocated _M_used "array" 307 // actually hosts (atomic) counters of reclaimed blocks: in 308 // _M_reserve_block and in _M_reclaim_block those numbers are 309 // subtracted from the first ones to obtain the actual size 310 // of the "working set" of the given thread. 311 // - Memory to these "arrays" is allocated in _S_initialize() 312 // for _S_max_threads + global pool 0. 313 size_t* _M_free; 314 size_t* _M_used; 315 316 // Each bin has its own mutex which is used to ensure data 317 // integrity while changing "ownership" on a block. The mutex 318 // is initialized in _S_initialize(). 319 __gthread_mutex_t* _M_mutex; 320 }; 321 322 // XXX GLIBCXX_ABI Deprecated 323 void 324 _M_initialize(__destroy_handler); 325 326 void 327 _M_initialize_once() 328 { 329 if (__builtin_expect(_M_init == false, false)) 330 _M_initialize(); 331 } 332 333 void 334 _M_destroy() throw(); 335 336 char* 337 _M_reserve_block(size_t __bytes, const size_t __thread_id); 338 339 void 340 _M_reclaim_block(char* __p, size_t __bytes) throw (); 341 342 const _Bin_record& 343 _M_get_bin(size_t __which) 344 { return _M_bin[__which]; } 345 346 void 347 _M_adjust_freelist(const _Bin_record& __bin, _Block_record* __block, 348 size_t __thread_id) 349 { 350 if (__gthread_active_p()) 351 { 352 __block->_M_thread_id = __thread_id; 353 --__bin._M_free[__thread_id]; 354 ++__bin._M_used[__thread_id]; 355 } 356 } 357 358 // XXX GLIBCXX_ABI Deprecated 359 void 360 _M_destroy_thread_key(void*) throw (); 361 362 size_t 363 _M_get_thread_id(); 364 365 explicit __pool() 366 : _M_bin(0), _M_bin_size(1), _M_thread_freelist(0) 367 { } 368 369 explicit __pool(const __pool_base::_Tune& __tune) 370 : __pool_base(__tune), _M_bin(0), _M_bin_size(1), 371 _M_thread_freelist(0) 372 { } 373 374 private: 375 // An "array" of bin_records each of which represents a specific 376 // power of 2 size. Memory to this "array" is allocated in 377 // _M_initialize(). 378 _Bin_record* _M_bin; 379 380 // Actual value calculated in _M_initialize(). 381 size_t _M_bin_size; 382 383 _Thread_record* _M_thread_freelist; 384 void* _M_thread_freelist_initial; 385 386 void 387 _M_initialize(); 388 }; 389 #endif 390 391 template<template <bool> class _PoolTp, bool _Thread> 392 struct __common_pool 393 { 394 typedef _PoolTp<_Thread> pool_type; 395 396 static pool_type& 397 _S_get_pool() 398 { 399 static pool_type _S_pool; 400 return _S_pool; 401 } 402 }; 403 404 template<template <bool> class _PoolTp, bool _Thread> 405 struct __common_pool_base; 406 407 template<template <bool> class _PoolTp> 408 struct __common_pool_base<_PoolTp, false> 409 : public __common_pool<_PoolTp, false> 410 { 411 using __common_pool<_PoolTp, false>::_S_get_pool; 412 413 static void 414 _S_initialize_once() 415 { 416 static bool __init; 417 if (__builtin_expect(__init == false, false)) 418 { 419 _S_get_pool()._M_initialize_once(); 420 __init = true; 421 } 422 } 423 }; 424 425 #ifdef __GTHREADS 426 template<template <bool> class _PoolTp> 427 struct __common_pool_base<_PoolTp, true> 428 : public __common_pool<_PoolTp, true> 429 { 430 using __common_pool<_PoolTp, true>::_S_get_pool; 431 432 static void 433 _S_initialize() 434 { _S_get_pool()._M_initialize_once(); } 435 436 static void 437 _S_initialize_once() 438 { 439 static bool __init; 440 if (__builtin_expect(__init == false, false)) 441 { 442 if (__gthread_active_p()) 443 { 444 // On some platforms, __gthread_once_t is an aggregate. 445 static __gthread_once_t __once = __GTHREAD_ONCE_INIT; 446 __gthread_once(&__once, _S_initialize); 447 } 448 449 // Double check initialization. May be necessary on some 450 // systems for proper construction when not compiling with 451 // thread flags. 452 _S_get_pool()._M_initialize_once(); 453 __init = true; 454 } 455 } 456 }; 457 #endif 458 459 /// Policy for shared __pool objects. 460 template<template <bool> class _PoolTp, bool _Thread> 461 struct __common_pool_policy : public __common_pool_base<_PoolTp, _Thread> 462 { 463 template<typename _Tp1, template <bool> class _PoolTp1 = _PoolTp, 464 bool _Thread1 = _Thread> 465 struct _M_rebind 466 { typedef __common_pool_policy<_PoolTp1, _Thread1> other; }; 467 468 using __common_pool_base<_PoolTp, _Thread>::_S_get_pool; 469 using __common_pool_base<_PoolTp, _Thread>::_S_initialize_once; 470 }; 471 472 473 template<typename _Tp, template <bool> class _PoolTp, bool _Thread> 474 struct __per_type_pool 475 { 476 typedef _Tp value_type; 477 typedef _PoolTp<_Thread> pool_type; 478 479 static pool_type& 480 _S_get_pool() 481 { 482 using std::size_t; 483 // Sane defaults for the _PoolTp. 484 typedef typename pool_type::_Block_record _Block_record; 485 const static size_t __a = (__alignof__(_Tp) >= sizeof(_Block_record) 486 ? __alignof__(_Tp) : sizeof(_Block_record)); 487 488 typedef typename __pool_base::_Tune _Tune; 489 static _Tune _S_tune(__a, sizeof(_Tp) * 64, 490 sizeof(_Tp) * 2 >= __a ? sizeof(_Tp) * 2 : __a, 491 sizeof(_Tp) * size_t(_Tune::_S_chunk_size), 492 _Tune::_S_max_threads, 493 _Tune::_S_freelist_headroom, 494 std::getenv("GLIBCXX_FORCE_NEW") ? true : false); 495 static pool_type _S_pool(_S_tune); 496 return _S_pool; 497 } 498 }; 499 500 template<typename _Tp, template <bool> class _PoolTp, bool _Thread> 501 struct __per_type_pool_base; 502 503 template<typename _Tp, template <bool> class _PoolTp> 504 struct __per_type_pool_base<_Tp, _PoolTp, false> 505 : public __per_type_pool<_Tp, _PoolTp, false> 506 { 507 using __per_type_pool<_Tp, _PoolTp, false>::_S_get_pool; 508 509 static void 510 _S_initialize_once() 511 { 512 static bool __init; 513 if (__builtin_expect(__init == false, false)) 514 { 515 _S_get_pool()._M_initialize_once(); 516 __init = true; 517 } 518 } 519 }; 520 521 #ifdef __GTHREADS 522 template<typename _Tp, template <bool> class _PoolTp> 523 struct __per_type_pool_base<_Tp, _PoolTp, true> 524 : public __per_type_pool<_Tp, _PoolTp, true> 525 { 526 using __per_type_pool<_Tp, _PoolTp, true>::_S_get_pool; 527 528 static void 529 _S_initialize() 530 { _S_get_pool()._M_initialize_once(); } 531 532 static void 533 _S_initialize_once() 534 { 535 static bool __init; 536 if (__builtin_expect(__init == false, false)) 537 { 538 if (__gthread_active_p()) 539 { 540 // On some platforms, __gthread_once_t is an aggregate. 541 static __gthread_once_t __once = __GTHREAD_ONCE_INIT; 542 __gthread_once(&__once, _S_initialize); 543 } 544 545 // Double check initialization. May be necessary on some 546 // systems for proper construction when not compiling with 547 // thread flags. 548 _S_get_pool()._M_initialize_once(); 549 __init = true; 550 } 551 } 552 }; 553 #endif 554 555 /// Policy for individual __pool objects. 556 template<typename _Tp, template <bool> class _PoolTp, bool _Thread> 557 struct __per_type_pool_policy 558 : public __per_type_pool_base<_Tp, _PoolTp, _Thread> 559 { 560 template<typename _Tp1, template <bool> class _PoolTp1 = _PoolTp, 561 bool _Thread1 = _Thread> 562 struct _M_rebind 563 { typedef __per_type_pool_policy<_Tp1, _PoolTp1, _Thread1> other; }; 564 565 using __per_type_pool_base<_Tp, _PoolTp, _Thread>::_S_get_pool; 566 using __per_type_pool_base<_Tp, _PoolTp, _Thread>::_S_initialize_once; 567 }; 568 569 570 /// Base class for _Tp dependent member functions. 571 template<typename _Tp> 572 class __mt_alloc_base 573 { 574 public: 575 typedef std::size_t size_type; 576 typedef std::ptrdiff_t difference_type; 577 typedef _Tp* pointer; 578 typedef const _Tp* const_pointer; 579 typedef _Tp& reference; 580 typedef const _Tp& const_reference; 581 typedef _Tp value_type; 582 583 #if __cplusplus >= 201103L 584 // _GLIBCXX_RESOLVE_LIB_DEFECTS 585 // 2103. propagate_on_container_move_assignment 586 typedef std::true_type propagate_on_container_move_assignment; 587 #endif 588 589 pointer 590 address(reference __x) const _GLIBCXX_NOEXCEPT 591 { return std::__addressof(__x); } 592 593 const_pointer 594 address(const_reference __x) const _GLIBCXX_NOEXCEPT 595 { return std::__addressof(__x); } 596 597 size_type 598 max_size() const _GLIBCXX_USE_NOEXCEPT 599 { return size_type(-1) / sizeof(_Tp); } 600 601 #if __cplusplus >= 201103L 602 template<typename _Up, typename... _Args> 603 void 604 construct(_Up* __p, _Args&&... __args) 605 { ::new((void *)__p) _Up(std::forward<_Args>(__args)...); } 606 607 template<typename _Up> 608 void 609 destroy(_Up* __p) { __p->~_Up(); } 610 #else 611 // _GLIBCXX_RESOLVE_LIB_DEFECTS 612 // 402. wrong new expression in [some_] allocator::construct 613 void 614 construct(pointer __p, const _Tp& __val) 615 { ::new((void *)__p) _Tp(__val); } 616 617 void 618 destroy(pointer __p) { __p->~_Tp(); } 619 #endif 620 }; 621 622 #ifdef __GTHREADS 623 #define __thread_default true 624 #else 625 #define __thread_default false 626 #endif 627 628 /** 629 * @brief This is a fixed size (power of 2) allocator which - when 630 * compiled with thread support - will maintain one freelist per 631 * size per thread plus a @a global one. Steps are taken to limit 632 * the per thread freelist sizes (by returning excess back to 633 * the @a global list). 634 * @ingroup allocators 635 * 636 * Further details: 637 * https://gcc.gnu.org/onlinedocs/libstdc++/manual/mt_allocator.html 638 */ 639 template<typename _Tp, 640 typename _Poolp = __common_pool_policy<__pool, __thread_default> > 641 class __mt_alloc : public __mt_alloc_base<_Tp> 642 { 643 public: 644 typedef std::size_t size_type; 645 typedef std::ptrdiff_t difference_type; 646 typedef _Tp* pointer; 647 typedef const _Tp* const_pointer; 648 typedef _Tp& reference; 649 typedef const _Tp& const_reference; 650 typedef _Tp value_type; 651 typedef _Poolp __policy_type; 652 typedef typename _Poolp::pool_type __pool_type; 653 654 template<typename _Tp1, typename _Poolp1 = _Poolp> 655 struct rebind 656 { 657 typedef typename _Poolp1::template _M_rebind<_Tp1>::other pol_type; 658 typedef __mt_alloc<_Tp1, pol_type> other; 659 }; 660 661 __mt_alloc() _GLIBCXX_USE_NOEXCEPT { } 662 663 __mt_alloc(const __mt_alloc&) _GLIBCXX_USE_NOEXCEPT { } 664 665 template<typename _Tp1, typename _Poolp1> 666 __mt_alloc(const __mt_alloc<_Tp1, _Poolp1>&) _GLIBCXX_USE_NOEXCEPT { } 667 668 ~__mt_alloc() _GLIBCXX_USE_NOEXCEPT { } 669 670 _GLIBCXX_NODISCARD pointer 671 allocate(size_type __n, const void* = 0); 672 673 void 674 deallocate(pointer __p, size_type __n); 675 676 const __pool_base::_Tune 677 _M_get_options() 678 { 679 // Return a copy, not a reference, for external consumption. 680 return __policy_type::_S_get_pool()._M_get_options(); 681 } 682 683 void 684 _M_set_options(__pool_base::_Tune __t) 685 { __policy_type::_S_get_pool()._M_set_options(__t); } 686 }; 687 688 template<typename _Tp, typename _Poolp> 689 _GLIBCXX_NODISCARD typename __mt_alloc<_Tp, _Poolp>::pointer 690 __mt_alloc<_Tp, _Poolp>:: 691 allocate(size_type __n, const void*) 692 { 693 if (__n > this->max_size()) 694 std::__throw_bad_alloc(); 695 696 #if __cpp_aligned_new 697 // Types with extended alignment are handled by operator new/delete. 698 if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__) 699 { 700 std::align_val_t __al = std::align_val_t(alignof(_Tp)); 701 return static_cast<_Tp*>(::operator new(__n * sizeof(_Tp), __al)); 702 } 703 #endif 704 705 __policy_type::_S_initialize_once(); 706 707 // Requests larger than _M_max_bytes are handled by operator 708 // new/delete directly. 709 __pool_type& __pool = __policy_type::_S_get_pool(); 710 const size_type __bytes = __n * sizeof(_Tp); 711 if (__pool._M_check_threshold(__bytes)) 712 { 713 void* __ret = ::operator new(__bytes); 714 return static_cast<_Tp*>(__ret); 715 } 716 717 // Round up to power of 2 and figure out which bin to use. 718 const size_type __which = __pool._M_get_binmap(__bytes); 719 const size_type __thread_id = __pool._M_get_thread_id(); 720 721 // Find out if we have blocks on our freelist. If so, go ahead 722 // and use them directly without having to lock anything. 723 char* __c; 724 typedef typename __pool_type::_Bin_record _Bin_record; 725 const _Bin_record& __bin = __pool._M_get_bin(__which); 726 if (__bin._M_first[__thread_id]) 727 { 728 // Already reserved. 729 typedef typename __pool_type::_Block_record _Block_record; 730 _Block_record* __block = __bin._M_first[__thread_id]; 731 __bin._M_first[__thread_id] = __block->_M_next; 732 733 __pool._M_adjust_freelist(__bin, __block, __thread_id); 734 __c = reinterpret_cast<char*>(__block) + __pool._M_get_align(); 735 } 736 else 737 { 738 // Null, reserve. 739 __c = __pool._M_reserve_block(__bytes, __thread_id); 740 } 741 return static_cast<_Tp*>(static_cast<void*>(__c)); 742 } 743 744 template<typename _Tp, typename _Poolp> 745 void 746 __mt_alloc<_Tp, _Poolp>:: 747 deallocate(pointer __p, size_type __n) 748 { 749 if (__builtin_expect(__p != 0, true)) 750 { 751 #if __cpp_aligned_new 752 // Types with extended alignment are handled by operator new/delete. 753 if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__) 754 { 755 ::operator delete(__p, std::align_val_t(alignof(_Tp))); 756 return; 757 } 758 #endif 759 760 // Requests larger than _M_max_bytes are handled by 761 // operators new/delete directly. 762 __pool_type& __pool = __policy_type::_S_get_pool(); 763 const size_type __bytes = __n * sizeof(_Tp); 764 if (__pool._M_check_threshold(__bytes)) 765 ::operator delete(__p); 766 else 767 __pool._M_reclaim_block(reinterpret_cast<char*>(__p), __bytes); 768 } 769 } 770 771 template<typename _Tp, typename _Poolp> 772 inline bool 773 operator==(const __mt_alloc<_Tp, _Poolp>&, const __mt_alloc<_Tp, _Poolp>&) 774 { return true; } 775 776 #if __cpp_impl_three_way_comparison < 201907L 777 template<typename _Tp, typename _Poolp> 778 inline bool 779 operator!=(const __mt_alloc<_Tp, _Poolp>&, const __mt_alloc<_Tp, _Poolp>&) 780 { return false; } 781 #endif 782 783 #undef __thread_default 784 785 _GLIBCXX_END_NAMESPACE_VERSION 786 } // namespace 787 788 #endif
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