单例模式模板

在平常的开发工作中，单例是我们经常使用的模式，经常我们需要写无数个单例类，现在提供一种单例模板：

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#pragma once   // common include #include <stdio.h> #include <stdlib.h> #include <assert.h>   // windows include  #if defined _WIN32 #else // linux include #include <errno.h> #endif       template <typename T> class Singleton { protected:     static T* singleton_; public:     Singleton(void)     {         assert(!singleton_); #if defined(_MSC_VER) && _MSC_VER < 1200          int offset = (int)(T*)1 - (int)(Singleton <T>*)(T*)1;         singleton_ = (T*)((int)this + offset); #else         singleton_ = static_cast< T* >(this); #endif     }                 ~Singleton(void){  assert(singleton_);  singleton_ = 0; }     static T& getSingleton(void) { assert(singleton_);  return (*singleton_); }     static T* getSingletonPtr(void){ return singleton_; } };   #define _SINGLETON_INIT( TYPE )                 template <>    TYPE * Singleton< TYPE >::singleton_ = 0;

用法: 
class A:public Singleton<A> 
{ 
}; 
在cpp文件中:

template<> A* Singleton<A>::singleton_ = 0;

_SINGLETON_INIT(A)