C++构造顺序

C++构造执行顺序：

一、先执行静态成员的构造函数，如果静态成员只是在类定义中声明了，而没有实现，是不用构造的。必须初始化后才执行其构造函数。

二、任何抽象基类的构造函数按照它们被继承的顺序构造（不是初始化列表中的顺序）
三、任何虚拟基类的构造函数按照它们被继承的顺序构造（不是初始化列表中的顺序）
四、任何非虚拟基类的构造函数按照它们被继承的顺序构造（不是初始化列表中的顺序）
五、任何成员对象的构造函数按照它们声明的顺序构造

六、类自己的构造函数 

注意：构造函数的执行顺序与初始化列表中的申明顺序无关，因为构造函数有多个，析构函数只有一个，析构顺序与构造顺序相反，析构的唯一性就限制了构造顺序的唯一性，故只能和继承顺序或申明的顺序来构造。

测试代码：

#include <iostream>#include "../Common/Common.h"using namespace std;class CBase{public:CBase(U32 id = 0) : m_base_id(id){cout << "CBase Create, id = " << m_base_id << endl;}~CBase(){cout << "CBase Destroy, id = " << m_base_id << endl;}U32 m_base_id;};class CBaseA : virtual public CBase{public:CBaseA(U32 a, U32 b = 0) : CBase(b) , m_baseA_id(a){cout << "CBaseA create, A id = " << m_baseA_id << endl;}~CBaseA(){cout << "CBaseA destroy, A id = " << m_baseA_id << endl;}U32 m_baseA_id;};class CBaseB : virtual public CBase{public:CBaseB(U32 a, U32 b = 0) : CBase(b), m_baseB_id(a){cout << "CBaseB create, B id = " << m_baseB_id << endl;}~CBaseB(){cout << "CBaseB destroy, B id = " << m_baseB_id << endl;}U32 m_baseB_id;};class CDerived : public CBaseA, public CBaseB/*, public CBase*/ /* 若采用虚继承，则不能再重复继承CBase，否则编译报错*/{public:CDerived(U32 a, U32 b, U32 c) : CBaseA(a), CBaseB(b), m_derived_id(a) /*, CBase(c)*/{cout << "CDerived create, Derived id = " << m_derived_id << endl;}~CDerived(){cout << "CDerived destroy, Derived id = " << m_derived_id << endl;}U32 m_derived_id;};int main(int argc, char* argv[]){CDerived obj(1, 2, 3);cout <<">>>>>>>>>>>>>>>> "<< obj.m_derived_id << endl;return 0;}

测试结果：

CBase Create, id = 0
CBaseA create, A id = 1
CBaseB create, B id = 2
CDerived create, Derived id = 1
>>>>>>>>>>>>>>>> 1
CDerived destroy, Derived id = 1
CBaseB destroy, B id = 2
CBaseA destroy, A id = 1
CBase Destroy, id = 0

测试结果说明，若采用虚继承，只会构造一次CBase。