1. 概述
STL Allocator是STL的內(nèi)存管理器，也是最低調(diào)的部分之一，你可能使用了3年stl，但卻不知其為何物。

STL標準如下介紹Allocator
the STL includes some low-level mechanisms for allocating and deallocating memory. Allocators are very specialized, and you can safely ignore them for almost all purposes. Allocators encapsulate allocation and deallocation of memory. They provide a low-level interface that permits efficient allocation of many small objects; different allocator types represent different schemes for memory management.
<STL 源碼剖析>將其描述為空間配置器，理由是allocator可以將其它存儲介質(zhì)（例如硬盤）做為stl 容器的存儲空間。由于內(nèi)存是allocator管理的主要部分，因此，本文以STL內(nèi)存管理為出發(fā)點介紹allocator。

Allocator就在我們身邊，通常使用STL的方式：
#include <vector>
std::vector<int> Array(100);

本質(zhì)上，調(diào)用的是：

#include <vector>
std::vector<int, std::allocator> Array(100);
std::allocator就是一個簡單的Allocator

2. 使用
針對不同的應用場合，STL中實現(xiàn)了不同的Allocator，如下（gcc-3.4：http://www.cs.huji.ac.il/~etsman/Docs/gcc-3.4-base/libstdc++/html/20_util/allocator.html）:

__gnu_cxx::new_allocator<T> Simply wraps ::operator new and ::operator delete.
__gnu_cxx::malloc_allocator<T> Simply wraps malloc and free. There is also a hook for an out-of-memory handler
__gnu_cxx::debug_allocator<T> A wrapper around an arbitrary allocator A. It passes on slightly increased size requests to A, and uses the extra memory to store size information.
__gnu_cxx::__pool_alloc<bool, int> A high-performance, single pool allocator. The reusable memory is shared among identical instantiations of this type.
__gnu_cxx::__mt_alloc<T> A high-performance fixed-size allocatorthat was initially developed specifically to suit the needs of multi threaded applications
__gnu_cxx::bitmap_allocato A high-performance allocator that uses a bit-map to keep track of the used and unused memory locations

例如，在多線程環(huán)境下，可以使用：