C++: undefined reference to vtable

单件模式如果按方法一写，所有用到单件模式的类声明中不允许再次定义构造和析构函数，但是类实现中必须实现构造和析构函数。如果不实现析构函数，就会报“undefined reference to 'vtable for classname'”错误。

单件模式一：

#define PATTERN_SINGLETON_DECLARE(classname) \

private: \

classname(); \

public: \

static classname * instance(); \

virtual ~classname();

#define PATTERN_SINGLETON_IMPLEMENT(classname) \

classname * classname::instance() \

{ \

static classname * _instance = NULL; \

if( NULL == _instance) \

{ \

_instance = new classname; \

} \

return _instance; \

}

单件模式二：

#define PATTERN_SINGLETON_DECLARE(classname) \

static classname * instance();

#define PATTERN_SINGLETON_IMPLEMENT(classname) \

classname * classname::instance() \

{ \

static classname * _instance = NULL; \

if( NULL == _instance) \

{ \

_instance = new classname; \

} \

return _instance; \

}

其他出现这个错误原因类似，虚函数的问题 http://hi.baidu.com/wind_stay/item/6c1e540a20812e163b53ee13