EffectiveC++3enewdelete(八)条款51：编写new和delete时需固守常规

#includevoid *operator new(std::size_t size) throw(std::bad_alloc)//你的operator new可能接受额外的参数
{using namespace std;if (0 &＃61;&＃61; size)//处理0-byte申请&＃xff0c;将它视为1-byte申请size &＃61; 1;while (true){尝试分配size byteif (分配成功)return &＃xff08;一个指针&＃xff0c;指向分配得来的内存&＃xff09;;//分配失败&＃xff0c;找出目前new-handling函数&＃xff08;见下&＃xff09;new_handler globalHandler &＃61; set_new_handler(0);set_new_handler(globalHandler);if (globalHandler)(*globalHandler)();elsethrow std::bad_alloc();}
}

class Base{
public:static void *operator new(std::size_t size) throw(std::bad_alloc);//...
};class Derived :public Base{//假设Derived未声明operator new//...
};Derived *p &＃61; new Derived;//这里调用的是Base::operator new

void *Base::operator new(std::size_t size) throw(std::bad_alloc)
{if (size !&＃61; sizeof(Base))//如果大小错误return ::operator new(size);//令标准的operator new起而处理...//否则&＃xff0c;在这里处理
}

void operator delete(void *rawMemory) throw()
{if (0 &＃61;&＃61; rawMemory)//如果将被删除的是个null指针&＃xff0c;那就什么都不用做return;现在&＃xff0c;归还rawMemory所指的内存;
}

class Base{//一如以往&＃xff0c;但此刻重点在operator delete
public:static void *operator new(std::size_t size) throw(std::bad_alloc);static void operator delete(void *rawMemory, std::size_t size) throw();...
};void Base::operator delete(void *rawMemory, std::size_t size) throw()
{if (rawMemory &＃61;&＃61; 0) return;//检查null指针if (size !&＃61; sizeof(Base))//如果大小错误&＃xff0c;并标准版operator delete处理此处申请{::operator delete(rawMemory);return;}现在&＃xff0c;归还rawMemory所指的内存;return;
}