标签：pre typename weak public type tom point struct typedef
shared_ptr定义如下：
template<typename _Tp> class shared_ptr {private: _Tp* _M_ptr; // contained pointer shared_count _M_refcount; // reference counter };
shared_count定义如下：
class shared_count { public: template<typename _Ptr, typename _Deleter> shared_count(_Ptr __p, _Deleter __d) : _M_pi(0) { _M_pi = new _Sp_counted_base_impl<_Ptr, _Deleter>(__p, __d); } private: _Sp_counted_base* _M_pi; };
_Sp_counted_base定义如下：
class _Sp_counted_base { private: _Atomic_word _M_use_count; // #shared _Atomic_word _M_weak_count; // #weak + (#shared != 0) __gnu_cxx::mutex_type _M_mutex; }; template<typename _Ptr, typename _Deleter> class _Sp_counted_base_impl : public _Sp_counted_base { private: _Ptr _M_ptr; // copy constructor must not throw _Deleter _M_del; // copy constructor must not throw };
sizeof(_Sp_counted_base) = 48，在_Sp_counted_base_Impl中，_Ptr是对象指针，而_M_del结构如下：
template<typename _Tp> struct _Sp_deleter { typedef void result_type; typedef _Tp* argument_type; void operator()(_Tp* p) const { delete p; } };
因此shared_ptr对象的体积为72：
标签：pre typename weak public type tom point struct typedef
原文地址：http://www.cnblogs.com/lvzhiqiang/p/6832306.html
