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gcc/libstdc++-v3/include/bits/stl_alloc.h

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// Allocators -*- C++ -*-
// Copyright (C) 2001, 2002 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 2, or (at your option)
// any later version.
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING. If not, write to the Free
// Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
// USA.
// As a special exception, you may use this file as part of a free software
// library without restriction. Specifically, if other files instantiate
// templates or use macros or inline functions from this file, or you compile
// this file and link it with other files to produce an executable, this
// file does not by itself cause the resulting executable to be covered by
// the GNU General Public License. This exception does not however
// invalidate any other reasons why the executable file might be covered by
// the GNU General Public License.
/*
* Copyright (c) 1996-1997
* Silicon Graphics Computer Systems, Inc.
*
* Permission to use, copy, modify, distribute and sell this software
* and its documentation for any purpose is hereby granted without fee,
* provided that the above copyright notice appear in all copies and
* that both that copyright notice and this permission notice appear
* in supporting documentation. Silicon Graphics makes no
* representations about the suitability of this software for any
* purpose. It is provided "as is" without express or implied warranty.
*/
/** @file stl_alloc.h
* This is an internal header file, included by other library headers.
* You should not attempt to use it directly.
*/
#ifndef __GLIBCPP_INTERNAL_ALLOC_H
#define __GLIBCPP_INTERNAL_ALLOC_H
/**
* @defgroup Allocators Memory Allocators
* @if maint
* stl_alloc.h implements some node allocators. These are NOT the same as
* allocators in the C++ standard, nor in the original H-P STL. They do not
* encapsulate different pointer types; we assume that there is only one
* pointer type. The C++ standard allocators are intended to allocate
* individual objects, not pools or arenas.
*
* In this file allocators are of two different styles: "standard" and
* "SGI" (quotes included). "Standard" allocators conform to 20.4. "SGI"
* allocators differ in AT LEAST the following ways (add to this list as you
* discover them):
*
* - "Standard" allocate() takes two parameters (n_count,hint=0) but "SGI"
* allocate() takes one paramter (n_size).
* - Likewise, "standard" deallocate()'s argument is a count, but in "SGI"
* is a byte size.
* - max_size(), construct(), and destroy() are missing in "SGI" allocators.
* - reallocate(p,oldsz,newsz) is added in "SGI", and behaves as
* if p=realloc(p,newsz).
*
* "SGI" allocators may be wrapped in __allocator to convert the interface
* into a "standard" one.
* @endif
*
* @note The @c reallocate member functions have been deprecated for 3.2
* and will be removed in 3.4. You must define @c _GLIBCPP_DEPRECATED
* to make this visible in 3.2; see c++config.h.
*
* The canonical description of these classes is in docs/html/ext/howto.html
* or online at http://gcc.gnu.org/onlinedocs/libstdc++/ext/howto.html#3
*/
#include <cstddef>
#include <cstdlib>
#include <cstring>
#include <cassert>
#include <bits/functexcept.h> // For __throw_bad_alloc
#include <bits/stl_threads.h>
#include <bits/atomicity.h>
namespace std
{
/**
* @if maint
* A new-based allocator, as required by the standard. Allocation and
* deallocation forward to global new and delete. "SGI" style, minus
* reallocate().
* @endif
* (See @link Allocators allocators info @endlink for more.)
*/
class __new_alloc
{
public:
static void*
allocate(size_t __n)
{ return ::operator new(__n); }
static void
deallocate(void* __p, size_t)
{ ::operator delete(__p); }
};
/**
* @if maint
* A malloc-based allocator. Typically slower than the
* __default_alloc_template (below). Typically thread-safe and more
* storage efficient. The template argument is unused and is only present
* to permit multiple instantiations (but see __default_alloc_template
* for caveats). "SGI" style, plus __set_malloc_handler for OOM conditions.
* @endif
* (See @link Allocators allocators info @endlink for more.)
*/
template<int __inst>
class __malloc_alloc_template
{
private:
static void* _S_oom_malloc(size_t);
#ifdef _GLIBCPP_DEPRECATED
static void* _S_oom_realloc(void*, size_t);
#endif
static void (* __malloc_alloc_oom_handler)();
public:
static void*
allocate(size_t __n)
{
void* __result = malloc(__n);
if (0 == __result) __result = _S_oom_malloc(__n);
return __result;
}
static void
deallocate(void* __p, size_t /* __n */)
{ free(__p); }
#ifdef _GLIBCPP_DEPRECATED
static void*
reallocate(void* __p, size_t /* old_sz */, size_t __new_sz)
{
void* __result = realloc(__p, __new_sz);
if (0 == __result)
__result = _S_oom_realloc(__p, __new_sz);
return __result;
}
#endif
static void (* __set_malloc_handler(void (*__f)()))()
{
void (* __old)() = __malloc_alloc_oom_handler;
__malloc_alloc_oom_handler = __f;
return __old;
}
};
// malloc_alloc out-of-memory handling
template<int __inst>
void (* __malloc_alloc_template<__inst>::__malloc_alloc_oom_handler)() = 0;
template<int __inst>
void*
__malloc_alloc_template<__inst>::
_S_oom_malloc(size_t __n)
{
void (* __my_malloc_handler)();
void* __result;
for (;;)
{
__my_malloc_handler = __malloc_alloc_oom_handler;
if (0 == __my_malloc_handler)
std::__throw_bad_alloc();
(*__my_malloc_handler)();
__result = malloc(__n);
if (__result)
return __result;
}
}
#ifdef _GLIBCPP_DEPRECATED
template<int __inst>
void*
__malloc_alloc_template<__inst>::
_S_oom_realloc(void* __p, size_t __n)
{
void (* __my_malloc_handler)();
void* __result;
for (;;)
{
__my_malloc_handler = __malloc_alloc_oom_handler;
if (0 == __my_malloc_handler)
std::__throw_bad_alloc();
(*__my_malloc_handler)();
__result = realloc(__p, __n);
if (__result)
return __result;
}
}
#endif
// Should not be referenced within the library anymore.
typedef __new_alloc __mem_interface;
/**
* @if maint
* This is used primarily (only?) in _Alloc_traits and other places to
* help provide the _Alloc_type typedef. All it does is forward the
* requests after some minimal checking.
*
* This is neither "standard"-conforming nor "SGI". The _Alloc parameter
* must be "SGI" style.
* @endif
* (See @link Allocators allocators info @endlink for more.)
*/
template<typename _Tp, typename _Alloc>
class __simple_alloc
{
public:
static _Tp*
allocate(size_t __n)
{ return 0 == __n ? 0 : (_Tp*) _Alloc::allocate(__n * sizeof (_Tp)); }
static _Tp*
allocate()
{ return (_Tp*) _Alloc::allocate(sizeof (_Tp)); }
static void
deallocate(_Tp* __p, size_t __n)
{ if (0 != __n) _Alloc::deallocate(__p, __n * sizeof (_Tp)); }
static void
deallocate(_Tp* __p)
{ _Alloc::deallocate(__p, sizeof (_Tp)); }
};
/**
* @if maint
* An adaptor for an underlying allocator (_Alloc) to check the size
* arguments for debugging. Errors are reported using assert; these
* checks can be disabled via NDEBUG, but the space penalty is still
* paid, therefore it is far better to just use the underlying allocator
* by itelf when no checking is desired.
*
* "There is some evidence that this can confuse Purify." - SGI comment
*
* This adaptor is "SGI" style. The _Alloc parameter must also be "SGI".
* @endif
* (See @link Allocators allocators info @endlink for more.)
*/
template<typename _Alloc>
class __debug_alloc
{
private:
// Size of space used to store size. Note that this must be
// large enough to preserve alignment.
enum {_S_extra = 8};
public:
static void*
allocate(size_t __n)
{
char* __result = (char*)_Alloc::allocate(__n + (int) _S_extra);
*(size_t*)__result = __n;
return __result + (int) _S_extra;
}
static void
deallocate(void* __p, size_t __n)
{
char* __real_p = (char*)__p - (int) _S_extra;
assert(*(size_t*)__real_p == __n);
_Alloc::deallocate(__real_p, __n + (int) _S_extra);
}
#ifdef _GLIBCPP_DEPRECATED
static void*
reallocate(void* __p, size_t __old_sz, size_t __new_sz)
{
char* __real_p = (char*)__p - (int) _S_extra;
assert(*(size_t*)__real_p == __old_sz);
char* __result = (char*)
_Alloc::reallocate(__real_p, __old_sz + (int) _S_extra,
__new_sz + (int) _S_extra);
*(size_t*)__result = __new_sz;
return __result + (int) _S_extra;
}
#endif
};
/**
* @if maint
* Default node allocator. "SGI" style. Uses various allocators to
* fulfill underlying requests (and makes as few requests as possible
* when in default high-speed pool mode).
*
* Important implementation properties:
* 0. If globally mandated, then allocate objects from __new_alloc
* 1. If the clients request an object of size > _MAX_BYTES, the resulting
* object will be obtained directly from __new_alloc
* 2. In all other cases, we allocate an object of size exactly
* _S_round_up(requested_size). Thus the client has enough size
* information that we can return the object to the proper free list
* without permanently losing part of the object.
*
* The first template parameter specifies whether more than one thread may
* use this allocator. It is safe to allocate an object from one instance
* of a default_alloc and deallocate it with another one. This effectively
* transfers its ownership to the second one. This may have undesirable
* effects on reference locality.
*
* The second parameter is unused and serves only to allow the creation of
* multiple default_alloc instances. Note that containers built on different
* allocator instances have different types, limiting the utility of this
* approach. If you do not wish to share the free lists with the main
* default_alloc instance, instantiate this with a non-zero __inst.
*
* @endif
* (See @link Allocators allocators info @endlink for more.)
*/
template<bool __threads, int __inst>
class __default_alloc_template
{
private:
enum {_ALIGN = 8};
enum {_MAX_BYTES = 128};
enum {_NFREELISTS = _MAX_BYTES / _ALIGN};
union _Obj
{
union _Obj* _M_free_list_link;
char _M_client_data[1]; // The client sees this.
};
static _Obj* volatile _S_free_list[_NFREELISTS];
// Chunk allocation state.
static char* _S_start_free;
static char* _S_end_free;
static size_t _S_heap_size;
static _STL_mutex_lock _S_node_allocator_lock;
static size_t
_S_round_up(size_t __bytes)
{ return (((__bytes) + (size_t) _ALIGN-1) & ~((size_t) _ALIGN - 1)); }
static size_t
_S_freelist_index(size_t __bytes)
{ return (((__bytes) + (size_t)_ALIGN-1)/(size_t)_ALIGN - 1); }
// Returns an object of size __n, and optionally adds to size __n
// free list.
static void*
_S_refill(size_t __n);
// Allocates a chunk for nobjs of size size. nobjs may be reduced
// if it is inconvenient to allocate the requested number.
static char*
_S_chunk_alloc(size_t __size, int& __nobjs);
// It would be nice to use _STL_auto_lock here. But we need a
// test whether threads are in use.
struct _Lock
{
_Lock() { if (__threads) _S_node_allocator_lock._M_acquire_lock(); }
~_Lock() { if (__threads) _S_node_allocator_lock._M_release_lock(); }
} __attribute__ ((__unused__));
friend struct _Lock;
static _Atomic_word _S_force_new;
public:
// __n must be > 0
static void*
allocate(size_t __n)
{
void* __ret = 0;
// If there is a race through here, assume answer from getenv
// will resolve in same direction. Inspired by techniques
// to efficiently support threading found in basic_string.h.
if (_S_force_new == 0)
{
if (getenv("GLIBCPP_FORCE_NEW"))
__atomic_add(&_S_force_new, 1);
else
__atomic_add(&_S_force_new, -1);
// Trust but verify...
assert (_S_force_new != 0);
}
if ((__n > (size_t) _MAX_BYTES) || (_S_force_new > 0))
__ret = __new_alloc::allocate(__n);
else
{
_Obj* volatile* __my_free_list = _S_free_list
+ _S_freelist_index(__n);
// Acquire the lock here with a constructor call. This
// ensures that it is released in exit or during stack
// unwinding.
_Lock __lock_instance;
_Obj* __restrict__ __result = *__my_free_list;
if (__result == 0)
__ret = _S_refill(_S_round_up(__n));
else
{
*__my_free_list = __result -> _M_free_list_link;
__ret = __result;
}
}
return __ret;
}
// __p may not be 0
static void
deallocate(void* __p, size_t __n)
{
if ((__n > (size_t) _MAX_BYTES) || (_S_force_new > 0))
__new_alloc::deallocate(__p, __n);
else
{
_Obj* volatile* __my_free_list = _S_free_list
+ _S_freelist_index(__n);
_Obj* __q = (_Obj*)__p;
// Acquire the lock here with a constructor call. This
// ensures that it is released in exit or during stack
// unwinding.
_Lock __lock_instance;
__q -> _M_free_list_link = *__my_free_list;
*__my_free_list = __q;
}
}
#ifdef _GLIBCPP_DEPRECATED
static void*
reallocate(void* __p, size_t __old_sz, size_t __new_sz);
#endif
};
template<bool __threads, int __inst> _Atomic_word
__default_alloc_template<__threads, __inst>::_S_force_new = 0;
template<bool __threads, int __inst>
inline bool
operator==(const __default_alloc_template<__threads,__inst>&,
const __default_alloc_template<__threads,__inst>&)
{ return true; }
template<bool __threads, int __inst>
inline bool
operator!=(const __default_alloc_template<__threads,__inst>&,
const __default_alloc_template<__threads,__inst>&)
{ return false; }
// We allocate memory in large chunks in order to avoid fragmenting the
// heap too much. We assume that __size is properly aligned. We hold
// the allocation lock.
template<bool __threads, int __inst>
char*
__default_alloc_template<__threads, __inst>::
_S_chunk_alloc(size_t __size, int& __nobjs)
{
char* __result;
size_t __total_bytes = __size * __nobjs;
size_t __bytes_left = _S_end_free - _S_start_free;
if (__bytes_left >= __total_bytes)
{
__result = _S_start_free;
_S_start_free += __total_bytes;
return __result ;
}
else if (__bytes_left >= __size)
{
__nobjs = (int)(__bytes_left/__size);
__total_bytes = __size * __nobjs;
__result = _S_start_free;
_S_start_free += __total_bytes;
return __result;
}
else
{
size_t __bytes_to_get =
2 * __total_bytes + _S_round_up(_S_heap_size >> 4);
// Try to make use of the left-over piece.
if (__bytes_left > 0)
{
_Obj* volatile* __my_free_list =
_S_free_list + _S_freelist_index(__bytes_left);
((_Obj*)_S_start_free) -> _M_free_list_link = *__my_free_list;
*__my_free_list = (_Obj*)_S_start_free;
}
_S_start_free = (char*) __new_alloc::allocate(__bytes_to_get);
if (0 == _S_start_free)
{
size_t __i;
_Obj* volatile* __my_free_list;
_Obj* __p;
// Try to make do with what we have. That can't hurt. We
// do not try smaller requests, since that tends to result
// in disaster on multi-process machines.
__i = __size;
for (; __i <= (size_t) _MAX_BYTES; __i += (size_t) _ALIGN)
{
__my_free_list = _S_free_list + _S_freelist_index(__i);
__p = *__my_free_list;
if (0 != __p)
{
*__my_free_list = __p -> _M_free_list_link;
_S_start_free = (char*)__p;
_S_end_free = _S_start_free + __i;
return _S_chunk_alloc(__size, __nobjs);
// Any leftover piece will eventually make it to the
// right free list.
}
}
_S_end_free = 0; // In case of exception.
_S_start_free = (char*)__new_alloc::allocate(__bytes_to_get);
// This should either throw an exception or remedy the situation.
// Thus we assume it succeeded.
}
_S_heap_size += __bytes_to_get;
_S_end_free = _S_start_free + __bytes_to_get;
return _S_chunk_alloc(__size, __nobjs);
}
}
// Returns an object of size __n, and optionally adds to "size
// __n"'s free list. We assume that __n is properly aligned. We
// hold the allocation lock.
template<bool __threads, int __inst>
void*
__default_alloc_template<__threads, __inst>::_S_refill(size_t __n)
{
int __nobjs = 20;
char* __chunk = _S_chunk_alloc(__n, __nobjs);
_Obj* volatile* __my_free_list;
_Obj* __result;
_Obj* __current_obj;
_Obj* __next_obj;
int __i;
if (1 == __nobjs)
return __chunk;
__my_free_list = _S_free_list + _S_freelist_index(__n);
// Build free list in chunk.
__result = (_Obj*)__chunk;
*__my_free_list = __next_obj = (_Obj*)(__chunk + __n);
for (__i = 1; ; __i++)
{
__current_obj = __next_obj;
__next_obj = (_Obj*)((char*)__next_obj + __n);
if (__nobjs - 1 == __i)
{
__current_obj -> _M_free_list_link = 0;
break;
}
else
__current_obj -> _M_free_list_link = __next_obj;
}
return(__result);
}
#ifdef _GLIBCPP_DEPRECATED
template<bool threads, int inst>
void*
__default_alloc_template<threads, inst>::
reallocate(void* __p, size_t __old_sz, size_t __new_sz)
{
void* __result;
size_t __copy_sz;
if (__old_sz > (size_t) _MAX_BYTES && __new_sz > (size_t) _MAX_BYTES)
return(realloc(__p, __new_sz));
if (_S_round_up(__old_sz) == _S_round_up(__new_sz))
return(__p);
__result = allocate(__new_sz);
__copy_sz = __new_sz > __old_sz? __old_sz : __new_sz;
memcpy(__result, __p, __copy_sz);
deallocate(__p, __old_sz);
return(__result);
}
#endif
template<bool __threads, int __inst>
_STL_mutex_lock
__default_alloc_template<__threads,__inst>::_S_node_allocator_lock
__STL_MUTEX_INITIALIZER;
template<bool __threads, int __inst>
char* __default_alloc_template<__threads,__inst>::_S_start_free = 0;
template<bool __threads, int __inst>
char* __default_alloc_template<__threads,__inst>::_S_end_free = 0;
template<bool __threads, int __inst>
size_t __default_alloc_template<__threads,__inst>::_S_heap_size = 0;
template<bool __threads, int __inst>
typename __default_alloc_template<__threads,__inst>::_Obj* volatile
__default_alloc_template<__threads,__inst>::_S_free_list[_NFREELISTS];
typedef __default_alloc_template<true,0> __alloc;
typedef __default_alloc_template<false,0> __single_client_alloc;
/**
* @brief The "standard" allocator, as per [20.4].
*
* The private _Alloc is "SGI" style. (See comments at the top
* of stl_alloc.h.)
*
* The underlying allocator behaves as follows.
* - __default_alloc_template is used via two typedefs
* - "__single_client_alloc" typedef does no locking for threads
* - "__alloc" typedef is threadsafe via the locks
* - __new_alloc is used for memory requests
*
* (See @link Allocators allocators info @endlink for more.)
*/
template<typename _Tp>
class allocator
{
typedef __alloc _Alloc; // The underlying allocator.
public:
typedef size_t size_type;
typedef ptrdiff_t difference_type;
typedef _Tp* pointer;
typedef const _Tp* const_pointer;
typedef _Tp& reference;
typedef const _Tp& const_reference;
typedef _Tp value_type;
template<typename _Tp1>
struct rebind
{ typedef allocator<_Tp1> other; };
allocator() throw() {}
allocator(const allocator&) throw() {}
template<typename _Tp1>
allocator(const allocator<_Tp1>&) throw() {}
~allocator() throw() {}
pointer
address(reference __x) const { return &__x; }
const_pointer
address(const_reference __x) const { return &__x; }
// __n is permitted to be 0. The C++ standard says nothing about what
// the return value is when __n == 0.
_Tp*
allocate(size_type __n, const void* = 0)
{
return __n != 0
? static_cast<_Tp*>(_Alloc::allocate(__n * sizeof(_Tp))) : 0;
}
// __p is not permitted to be a null pointer.
void
deallocate(pointer __p, size_type __n)
{ _Alloc::deallocate(__p, __n * sizeof(_Tp)); }
size_type
max_size() const throw() { return size_t(-1) / sizeof(_Tp); }
void construct(pointer __p, const _Tp& __val) { new(__p) _Tp(__val); }
void destroy(pointer __p) { __p->~_Tp(); }
};
template<>
class allocator<void>
{
public:
typedef size_t size_type;
typedef ptrdiff_t difference_type;
typedef void* pointer;
typedef const void* const_pointer;
typedef void value_type;
template<typename _Tp1>
struct rebind
{ typedef allocator<_Tp1> other; };
};
template<typename _T1, typename _T2>
inline bool
operator==(const allocator<_T1>&, const allocator<_T2>&)
{ return true; }
template<typename _T1, typename _T2>
inline bool
operator!=(const allocator<_T1>&, const allocator<_T2>&)
{ return false; }
/**
* @if maint
* Allocator adaptor to turn an "SGI" style allocator (e.g., __alloc,
* __malloc_alloc_template) into a "standard" conforming allocator. Note
* that this adaptor does *not* assume that all objects of the underlying
* alloc class are identical, nor does it assume that all of the underlying
* alloc's member functions are static member functions. Note, also, that
* __allocator<_Tp, __alloc> is essentially the same thing as allocator<_Tp>.
* @endif
* (See @link Allocators allocators info @endlink for more.)
*/
template<typename _Tp, typename _Alloc>
struct __allocator
{
_Alloc __underlying_alloc;
typedef size_t size_type;
typedef ptrdiff_t difference_type;
typedef _Tp* pointer;
typedef const _Tp* const_pointer;
typedef _Tp& reference;
typedef const _Tp& const_reference;
typedef _Tp value_type;
template<typename _Tp1>
struct rebind
{ typedef __allocator<_Tp1, _Alloc> other; };
__allocator() throw() {}
__allocator(const __allocator& __a) throw()
: __underlying_alloc(__a.__underlying_alloc) {}
template<typename _Tp1>
__allocator(const __allocator<_Tp1, _Alloc>& __a) throw()
: __underlying_alloc(__a.__underlying_alloc) {}
~__allocator() throw() {}
pointer
address(reference __x) const { return &__x; }
const_pointer
address(const_reference __x) const { return &__x; }
// __n is permitted to be 0.
_Tp*
allocate(size_type __n, const void* = 0)
{
return __n != 0
? static_cast<_Tp*>(__underlying_alloc.allocate(__n * sizeof(_Tp)))
: 0;
}
// __p is not permitted to be a null pointer.
void
deallocate(pointer __p, size_type __n)
{ __underlying_alloc.deallocate(__p, __n * sizeof(_Tp)); }
size_type
max_size() const throw() { return size_t(-1) / sizeof(_Tp); }
void
construct(pointer __p, const _Tp& __val) { new(__p) _Tp(__val); }
void
destroy(pointer __p) { __p->~_Tp(); }
};
template<typename _Alloc>
struct __allocator<void, _Alloc>
{
typedef size_t size_type;
typedef ptrdiff_t difference_type;
typedef void* pointer;
typedef const void* const_pointer;
typedef void value_type;
template<typename _Tp1>
struct rebind
{ typedef __allocator<_Tp1, _Alloc> other; };
};
template<typename _Tp, typename _Alloc>
inline bool
operator==(const __allocator<_Tp,_Alloc>& __a1,
const __allocator<_Tp,_Alloc>& __a2)
{ return __a1.__underlying_alloc == __a2.__underlying_alloc; }
template<typename _Tp, typename _Alloc>
inline bool
operator!=(const __allocator<_Tp, _Alloc>& __a1,
const __allocator<_Tp, _Alloc>& __a2)
{ return __a1.__underlying_alloc != __a2.__underlying_alloc; }
//@{
/** Comparison operators for all of the predifined SGI-style allocators.
* This ensures that __allocator<malloc_alloc> (for example) will work
* correctly. As required, all allocators compare equal.
*/
template<int inst>
inline bool
operator==(const __malloc_alloc_template<inst>&,
const __malloc_alloc_template<inst>&)
{ return true; }
template<int __inst>
inline bool
operator!=(const __malloc_alloc_template<__inst>&,
const __malloc_alloc_template<__inst>&)
{ return false; }
template<typename _Alloc>
inline bool
operator==(const __debug_alloc<_Alloc>&, const __debug_alloc<_Alloc>&)
{ return true; }
template<typename _Alloc>
inline bool
operator!=(const __debug_alloc<_Alloc>&, const __debug_alloc<_Alloc>&)
{ return false; }
//@}
/**
* @if maint
* Another allocator adaptor: _Alloc_traits. This serves two purposes.
* First, make it possible to write containers that can use either "SGI"
* style allocators or "standard" allocators. Second, provide a mechanism
* so that containers can query whether or not the allocator has distinct
* instances. If not, the container can avoid wasting a word of memory to
* store an empty object. For examples of use, see stl_vector.h, etc, or
* any of the other classes derived from this one.
*
* This adaptor uses partial specialization. The general case of
* _Alloc_traits<_Tp, _Alloc> assumes that _Alloc is a
* standard-conforming allocator, possibly with non-equal instances and
* non-static members. (It still behaves correctly even if _Alloc has
* static member and if all instances are equal. Refinements affect
* performance, not correctness.)
*
* There are always two members: allocator_type, which is a standard-
* conforming allocator type for allocating objects of type _Tp, and
* _S_instanceless, a static const member of type bool. If
* _S_instanceless is true, this means that there is no difference
* between any two instances of type allocator_type. Furthermore, if
* _S_instanceless is true, then _Alloc_traits has one additional
* member: _Alloc_type. This type encapsulates allocation and
* deallocation of objects of type _Tp through a static interface; it
* has two member functions, whose signatures are
*
* - static _Tp* allocate(size_t)
* - static void deallocate(_Tp*, size_t)
*
* The size_t parameters are "standard" style (see top of stl_alloc.h) in
* that they take counts, not sizes.
*
* @endif
* (See @link Allocators allocators info @endlink for more.)
*/
//@{
// The fully general version.
template<typename _Tp, typename _Allocator>
struct _Alloc_traits
{
static const bool _S_instanceless = false;
typedef typename _Allocator::template rebind<_Tp>::other allocator_type;
};
template<typename _Tp, typename _Allocator>
const bool _Alloc_traits<_Tp, _Allocator>::_S_instanceless;
/// The version for the default allocator.
template<typename _Tp, typename _Tp1>
struct _Alloc_traits<_Tp, allocator<_Tp1> >
{
static const bool _S_instanceless = true;
typedef __simple_alloc<_Tp, __alloc> _Alloc_type;
typedef allocator<_Tp> allocator_type;
};
//@}
//@{
/// Versions for the predefined "SGI" style allocators.
template<typename _Tp, int __inst>
struct _Alloc_traits<_Tp, __malloc_alloc_template<__inst> >
{
static const bool _S_instanceless = true;
typedef __simple_alloc<_Tp, __malloc_alloc_template<__inst> > _Alloc_type;
typedef __allocator<_Tp, __malloc_alloc_template<__inst> > allocator_type;
};
template<typename _Tp, bool __threads, int __inst>
struct _Alloc_traits<_Tp, __default_alloc_template<__threads, __inst> >
{
static const bool _S_instanceless = true;
typedef __simple_alloc<_Tp, __default_alloc_template<__threads, __inst> >
_Alloc_type;
typedef __allocator<_Tp, __default_alloc_template<__threads, __inst> >
allocator_type;
};
template<typename _Tp, typename _Alloc>
struct _Alloc_traits<_Tp, __debug_alloc<_Alloc> >
{
static const bool _S_instanceless = true;
typedef __simple_alloc<_Tp, __debug_alloc<_Alloc> > _Alloc_type;
typedef __allocator<_Tp, __debug_alloc<_Alloc> > allocator_type;
};
//@}
//@{
/// Versions for the __allocator adaptor used with the predefined
/// "SGI" style allocators.
template<typename _Tp, typename _Tp1, int __inst>
struct _Alloc_traits<_Tp,
__allocator<_Tp1, __malloc_alloc_template<__inst> > >
{
static const bool _S_instanceless = true;
typedef __simple_alloc<_Tp, __malloc_alloc_template<__inst> > _Alloc_type;
typedef __allocator<_Tp, __malloc_alloc_template<__inst> > allocator_type;
};
template<typename _Tp, typename _Tp1, bool __thr, int __inst>
struct _Alloc_traits<_Tp, __allocator<_Tp1, __default_alloc_template<__thr, __inst> > >
{
static const bool _S_instanceless = true;
typedef __simple_alloc<_Tp, __default_alloc_template<__thr,__inst> >
_Alloc_type;
typedef __allocator<_Tp, __default_alloc_template<__thr,__inst> >
allocator_type;
};
template<typename _Tp, typename _Tp1, typename _Alloc>
struct _Alloc_traits<_Tp, __allocator<_Tp1, __debug_alloc<_Alloc> > >
{
static const bool _S_instanceless = true;
typedef __simple_alloc<_Tp, __debug_alloc<_Alloc> > _Alloc_type;
typedef __allocator<_Tp, __debug_alloc<_Alloc> > allocator_type;
};
//@}
// Inhibit implicit instantiations for required instantiations,
// which are defined via explicit instantiations elsewhere.
// NB: This syntax is a GNU extension.
extern template class allocator<char>;
extern template class allocator<wchar_t>;
extern template class __default_alloc_template<true,0>;
} // namespace std
#endif
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