281 lines
8.2 KiB
C++
281 lines
8.2 KiB
C++
// Allocators -*- C++ -*-
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// Copyright (C) 2001-2016 Free Software Foundation, Inc.
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//
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// This file is part of the GNU ISO C++ Library. This library is free
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// software; you can redistribute it and/or modify it under the
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// terms of the GNU General Public License as published by the
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// Free Software Foundation; either version 3, or (at your option)
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// any later version.
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// Under Section 7 of GPL version 3, you are granted additional
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// permissions described in the GCC Runtime Library Exception, version
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// 3.1, as published by the Free Software Foundation.
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// You should have received a copy of the GNU General Public License and
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// a copy of the GCC Runtime Library Exception along with this program;
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// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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// <http://www.gnu.org/licenses/>.
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/*
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* Copyright (c) 1996-1997
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* Silicon Graphics Computer Systems, Inc.
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*
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* Permission to use, copy, modify, distribute and sell this software
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* and its documentation for any purpose is hereby granted without fee,
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* provided that the above copyright notice appear in all copies and
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* that both that copyright notice and this permission notice appear
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* in supporting documentation. Silicon Graphics makes no
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* representations about the suitability of this software for any
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* purpose. It is provided "as is" without express or implied warranty.
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*/
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/** @file ext/pool_allocator.h
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* This file is a GNU extension to the Standard C++ Library.
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*/
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#ifndef _POOL_ALLOCATOR_H
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#define _POOL_ALLOCATOR_H 1
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#include <bits/c++config.h>
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#include <cstdlib>
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#include <new>
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#include <bits/functexcept.h>
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#include <ext/atomicity.h>
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#include <ext/concurrence.h>
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#include <bits/move.h>
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#if __cplusplus >= 201103L
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#include <type_traits>
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#endif
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namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
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{
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_GLIBCXX_BEGIN_NAMESPACE_VERSION
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using std::size_t;
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using std::ptrdiff_t;
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/**
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* @brief Base class for __pool_alloc.
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*
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* Uses various allocators to fulfill underlying requests (and makes as
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* few requests as possible when in default high-speed pool mode).
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*
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* Important implementation properties:
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* 0. If globally mandated, then allocate objects from new
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* 1. If the clients request an object of size > _S_max_bytes, the resulting
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* object will be obtained directly from new
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* 2. In all other cases, we allocate an object of size exactly
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* _S_round_up(requested_size). Thus the client has enough size
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* information that we can return the object to the proper free list
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* without permanently losing part of the object.
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*/
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class __pool_alloc_base
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{
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protected:
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enum { _S_align = 8 };
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enum { _S_max_bytes = 128 };
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enum { _S_free_list_size = (size_t)_S_max_bytes / (size_t)_S_align };
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union _Obj
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{
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union _Obj* _M_free_list_link;
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char _M_client_data[1]; // The client sees this.
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};
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static _Obj* volatile _S_free_list[_S_free_list_size];
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// Chunk allocation state.
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static char* _S_start_free;
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static char* _S_end_free;
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static size_t _S_heap_size;
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size_t
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_M_round_up(size_t __bytes)
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{ return ((__bytes + (size_t)_S_align - 1) & ~((size_t)_S_align - 1)); }
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_GLIBCXX_CONST _Obj* volatile*
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_M_get_free_list(size_t __bytes) throw ();
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__mutex&
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_M_get_mutex() throw ();
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// Returns an object of size __n, and optionally adds to size __n
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// free list.
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void*
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_M_refill(size_t __n);
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// Allocates a chunk for nobjs of size size. nobjs may be reduced
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// if it is inconvenient to allocate the requested number.
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char*
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_M_allocate_chunk(size_t __n, int& __nobjs);
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};
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/**
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* @brief Allocator using a memory pool with a single lock.
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* @ingroup allocators
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*/
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template<typename _Tp>
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class __pool_alloc : private __pool_alloc_base
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{
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private:
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static _Atomic_word _S_force_new;
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public:
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typedef size_t size_type;
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typedef ptrdiff_t difference_type;
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typedef _Tp* pointer;
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typedef const _Tp* const_pointer;
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typedef _Tp& reference;
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typedef const _Tp& const_reference;
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typedef _Tp value_type;
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template<typename _Tp1>
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struct rebind
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{ typedef __pool_alloc<_Tp1> other; };
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#if __cplusplus >= 201103L
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// _GLIBCXX_RESOLVE_LIB_DEFECTS
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// 2103. propagate_on_container_move_assignment
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typedef std::true_type propagate_on_container_move_assignment;
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#endif
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__pool_alloc() _GLIBCXX_USE_NOEXCEPT { }
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__pool_alloc(const __pool_alloc&) _GLIBCXX_USE_NOEXCEPT { }
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template<typename _Tp1>
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__pool_alloc(const __pool_alloc<_Tp1>&) _GLIBCXX_USE_NOEXCEPT { }
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~__pool_alloc() _GLIBCXX_USE_NOEXCEPT { }
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pointer
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address(reference __x) const _GLIBCXX_NOEXCEPT
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{ return std::__addressof(__x); }
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const_pointer
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address(const_reference __x) const _GLIBCXX_NOEXCEPT
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{ return std::__addressof(__x); }
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size_type
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max_size() const _GLIBCXX_USE_NOEXCEPT
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{ return size_t(-1) / sizeof(_Tp); }
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#if __cplusplus >= 201103L
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template<typename _Up, typename... _Args>
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void
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construct(_Up* __p, _Args&&... __args)
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{ ::new((void *)__p) _Up(std::forward<_Args>(__args)...); }
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template<typename _Up>
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void
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destroy(_Up* __p) { __p->~_Up(); }
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#else
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// _GLIBCXX_RESOLVE_LIB_DEFECTS
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// 402. wrong new expression in [some_] allocator::construct
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void
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construct(pointer __p, const _Tp& __val)
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{ ::new((void *)__p) _Tp(__val); }
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void
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destroy(pointer __p) { __p->~_Tp(); }
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#endif
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pointer
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allocate(size_type __n, const void* = 0);
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void
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deallocate(pointer __p, size_type __n);
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};
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template<typename _Tp>
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inline bool
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operator==(const __pool_alloc<_Tp>&, const __pool_alloc<_Tp>&)
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{ return true; }
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template<typename _Tp>
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inline bool
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operator!=(const __pool_alloc<_Tp>&, const __pool_alloc<_Tp>&)
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{ return false; }
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template<typename _Tp>
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_Atomic_word
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__pool_alloc<_Tp>::_S_force_new;
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template<typename _Tp>
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_Tp*
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__pool_alloc<_Tp>::allocate(size_type __n, const void*)
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{
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pointer __ret = 0;
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if (__builtin_expect(__n != 0, true))
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{
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if (__n > this->max_size())
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std::__throw_bad_alloc();
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// If there is a race through here, assume answer from getenv
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// will resolve in same direction. Inspired by techniques
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// to efficiently support threading found in basic_string.h.
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if (_S_force_new == 0)
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{
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if (std::getenv("GLIBCXX_FORCE_NEW"))
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__atomic_add_dispatch(&_S_force_new, 1);
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else
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__atomic_add_dispatch(&_S_force_new, -1);
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}
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const size_t __bytes = __n * sizeof(_Tp);
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if (__bytes > size_t(_S_max_bytes) || _S_force_new > 0)
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__ret = static_cast<_Tp*>(::operator new(__bytes));
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else
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{
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_Obj* volatile* __free_list = _M_get_free_list(__bytes);
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__scoped_lock sentry(_M_get_mutex());
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_Obj* __restrict__ __result = *__free_list;
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if (__builtin_expect(__result == 0, 0))
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__ret = static_cast<_Tp*>(_M_refill(_M_round_up(__bytes)));
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else
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{
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*__free_list = __result->_M_free_list_link;
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__ret = reinterpret_cast<_Tp*>(__result);
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}
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if (__ret == 0)
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std::__throw_bad_alloc();
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}
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}
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return __ret;
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}
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template<typename _Tp>
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void
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__pool_alloc<_Tp>::deallocate(pointer __p, size_type __n)
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{
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if (__builtin_expect(__n != 0 && __p != 0, true))
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{
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const size_t __bytes = __n * sizeof(_Tp);
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if (__bytes > static_cast<size_t>(_S_max_bytes) || _S_force_new > 0)
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::operator delete(__p);
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else
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{
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_Obj* volatile* __free_list = _M_get_free_list(__bytes);
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_Obj* __q = reinterpret_cast<_Obj*>(__p);
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__scoped_lock sentry(_M_get_mutex());
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__q ->_M_free_list_link = *__free_list;
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*__free_list = __q;
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}
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}
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}
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_GLIBCXX_END_NAMESPACE_VERSION
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} // namespace
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#endif
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