libstdc++
debug_allocator.h
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00001 // Allocators -*- C++ -*-
00002 
00003 // Copyright (C) 2001, 2002, 2003, 2004, 2005, 2009, 2010
00004 // Free Software Foundation, Inc.
00005 //
00006 // This file is part of the GNU ISO C++ Library.  This library is free
00007 // software; you can redistribute it and/or modify it under the
00008 // terms of the GNU General Public License as published by the
00009 // Free Software Foundation; either version 3, or (at your option)
00010 // any later version.
00011 
00012 // This library is distributed in the hope that it will be useful,
00013 // but WITHOUT ANY WARRANTY; without even the implied warranty of
00014 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00015 // GNU General Public License for more details.
00016 
00017 // Under Section 7 of GPL version 3, you are granted additional
00018 // permissions described in the GCC Runtime Library Exception, version
00019 // 3.1, as published by the Free Software Foundation.
00020 
00021 // You should have received a copy of the GNU General Public License and
00022 // a copy of the GCC Runtime Library Exception along with this program;
00023 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
00024 // <http://www.gnu.org/licenses/>.
00025 
00026 /*
00027  * Copyright (c) 1996-1997
00028  * Silicon Graphics Computer Systems, Inc.
00029  *
00030  * Permission to use, copy, modify, distribute and sell this software
00031  * and its documentation for any purpose is hereby granted without fee,
00032  * provided that the above copyright notice appear in all copies and
00033  * that both that copyright notice and this permission notice appear
00034  * in supporting documentation.  Silicon Graphics makes no
00035  * representations about the suitability of this software for any
00036  * purpose.  It is provided "as is" without express or implied warranty.
00037  */
00038 
00039 /** @file ext/debug_allocator.h
00040  *  This file is a GNU extension to the Standard C++ Library.
00041  */
00042 
00043 #ifndef _DEBUG_ALLOCATOR_H
00044 #define _DEBUG_ALLOCATOR_H 1
00045 
00046 #include <stdexcept>
00047 
00048 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
00049 {
00050 _GLIBCXX_BEGIN_NAMESPACE_VERSION
00051 
00052   using std::size_t;
00053 
00054   /**
00055    *  @brief  A meta-allocator with debugging bits, as per [20.4].
00056    *  @ingroup allocators
00057    *
00058    *  This is precisely the allocator defined in the C++ Standard. 
00059    *    - all allocation calls operator new
00060    *    - all deallocation calls operator delete
00061    */
00062   template<typename _Alloc>
00063     class debug_allocator
00064     {
00065     public:
00066       typedef typename _Alloc::size_type        size_type;
00067       typedef typename _Alloc::difference_type  difference_type;
00068       typedef typename _Alloc::pointer          pointer;
00069       typedef typename _Alloc::const_pointer    const_pointer;
00070       typedef typename _Alloc::reference        reference;
00071       typedef typename _Alloc::const_reference  const_reference;
00072       typedef typename _Alloc::value_type       value_type;
00073 
00074     private:
00075       // _M_extra is the number of objects that correspond to the
00076       // extra space where debug information is stored.
00077       size_type         _M_extra;
00078       
00079       _Alloc            _M_allocator;
00080 
00081     public:
00082       debug_allocator()
00083       {
00084     const size_t __obj_size = sizeof(value_type);
00085     _M_extra = (sizeof(size_type) + __obj_size - 1) / __obj_size; 
00086       }
00087       
00088       pointer
00089       allocate(size_type __n)
00090       {
00091         pointer __res = _M_allocator.allocate(__n + _M_extra);      
00092     size_type* __ps = reinterpret_cast<size_type*>(__res);
00093     *__ps = __n;
00094         return __res + _M_extra;
00095       }
00096 
00097       pointer
00098       allocate(size_type __n, const void* __hint)
00099       {
00100         pointer __res = _M_allocator.allocate(__n + _M_extra, __hint);
00101     size_type* __ps = reinterpret_cast<size_type*>(__res);
00102     *__ps = __n;
00103         return __res + _M_extra;
00104       }
00105 
00106       void
00107       deallocate(pointer __p, size_type __n)
00108       {
00109     if (__p)
00110       {
00111         pointer __real_p = __p - _M_extra;
00112         if (*reinterpret_cast<size_type*>(__real_p) != __n)
00113           {
00114         throw std::runtime_error("debug_allocator::deallocate"
00115                      " wrong size");
00116           }
00117         _M_allocator.deallocate(__real_p, __n + _M_extra);
00118       }
00119     else
00120       throw std::runtime_error("debug_allocator::deallocate null pointer");
00121       }
00122     };
00123 
00124 _GLIBCXX_END_NAMESPACE_VERSION
00125 } // namespace
00126 
00127 #endif