debug_allocator.h

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00001 // Allocators -*- C++ -*-
00002 
00003 // Copyright (C) 2001, 2002, 2003, 2004, 2005, 2009 Free Software Foundation, Inc.
00004 //
00005 // This file is part of the GNU ISO C++ Library.  This library is free
00006 // software; you can redistribute it and/or modify it under the
00007 // terms of the GNU General Public License as published by the
00008 // Free Software Foundation; either version 3, or (at your option)
00009 // any later version.
00010 
00011 // This library is distributed in the hope that it will be useful,
00012 // but WITHOUT ANY WARRANTY; without even the implied warranty of
00013 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00014 // GNU General Public License for more details.
00015 
00016 // Under Section 7 of GPL version 3, you are granted additional
00017 // permissions described in the GCC Runtime Library Exception, version
00018 // 3.1, as published by the Free Software Foundation.
00019 
00020 // You should have received a copy of the GNU General Public License and
00021 // a copy of the GCC Runtime Library Exception along with this program;
00022 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
00023 // <http://www.gnu.org/licenses/>.
00024 
00025 /*
00026  * Copyright (c) 1996-1997
00027  * Silicon Graphics Computer Systems, Inc.
00028  *
00029  * Permission to use, copy, modify, distribute and sell this software
00030  * and its documentation for any purpose is hereby granted without fee,
00031  * provided that the above copyright notice appear in all copies and
00032  * that both that copyright notice and this permission notice appear
00033  * in supporting documentation.  Silicon Graphics makes no
00034  * representations about the suitability of this software for any
00035  * purpose.  It is provided "as is" without express or implied warranty.
00036  */
00037 
00038 /** @file ext/debug_allocator.h
00039  *  This file is a GNU extension to the Standard C++ Library.
00040  *  You should only include this header if you are using GCC 3 or later.
00041  */
00042 
00043 #ifndef _DEBUG_ALLOCATOR_H
00044 #define _DEBUG_ALLOCATOR_H 1
00045 
00046 #include <stdexcept>
00047 
00048 _GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx)
00049 
00050   using std::size_t;
00051 
00052   /**
00053    *  @brief  A meta-allocator with debugging bits, as per [20.4].
00054    *  @ingroup allocators
00055    *
00056    *  This is precisely the allocator defined in the C++ Standard. 
00057    *    - all allocation calls operator new
00058    *    - all deallocation calls operator delete
00059    */
00060   template<typename _Alloc>
00061     class debug_allocator
00062     {
00063     public:
00064       typedef typename _Alloc::size_type        size_type;
00065       typedef typename _Alloc::difference_type  difference_type;
00066       typedef typename _Alloc::pointer          pointer;
00067       typedef typename _Alloc::const_pointer    const_pointer;
00068       typedef typename _Alloc::reference        reference;
00069       typedef typename _Alloc::const_reference  const_reference;
00070       typedef typename _Alloc::value_type       value_type;
00071 
00072     private:
00073       // _M_extra is the number of objects that correspond to the
00074       // extra space where debug information is stored.
00075       size_type         _M_extra;
00076       
00077       _Alloc            _M_allocator;
00078 
00079     public:
00080       debug_allocator()
00081       {
00082     const size_t __obj_size = sizeof(value_type);
00083     _M_extra = (sizeof(size_type) + __obj_size - 1) / __obj_size; 
00084       }
00085       
00086       pointer
00087       allocate(size_type __n)
00088       {
00089         pointer __res = _M_allocator.allocate(__n + _M_extra);      
00090     size_type* __ps = reinterpret_cast<size_type*>(__res);
00091     *__ps = __n;
00092         return __res + _M_extra;
00093       }
00094 
00095       pointer
00096       allocate(size_type __n, const void* __hint)
00097       {
00098         pointer __res = _M_allocator.allocate(__n + _M_extra, __hint);
00099     size_type* __ps = reinterpret_cast<size_type*>(__res);
00100     *__ps = __n;
00101         return __res + _M_extra;
00102       }
00103 
00104       void
00105       deallocate(pointer __p, size_type __n)
00106       {
00107     if (__p)
00108       {
00109         pointer __real_p = __p - _M_extra;
00110         if (*reinterpret_cast<size_type*>(__real_p) != __n)
00111           {
00112         throw std::runtime_error("debug_allocator::deallocate"
00113                      " wrong size");
00114           }
00115         _M_allocator.deallocate(__real_p, __n + _M_extra);
00116       }
00117     else
00118       throw std::runtime_error("debug_allocator::deallocate null pointer");
00119       }
00120     };
00121 
00122 _GLIBCXX_END_NAMESPACE
00123 
00124 #endif

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