C++系统自己主动生成默认构造函数的情况

(1) 基类存在默认构造函数

class CBaseClass
{
public:

CBaseClass()
{
m_i = 0;
}

private:

int m_i;
};


class CDriveClass: public CBaseClass
{
public:

void func()
{
}

private:

};

(2) 成员变量存在默认构造函数

class CTestClass
{
public:

CTestClass()
{
m_i = 1;
}

private:

int m_i;
};

class CDriveClass
{
public:
 void func()
{
}

private:

CTestClass mTestClass;
};

(3) 存在虚函数：初始化虚函数指针

class CDriveClass: virtual public CBaseClass  //: public CBaseClass
{
public:

 void func()
{
}

};

(4) 存在虚基类：初始化虚基类指针

class CBaseClass
{
};


class CDriveClass: virtual public CBaseClass
{
public:

void func()
{
}
};

详细能够查看反汇编代码：Visual Stdio 2010编译器中：Debug->windows->Disassembly

--汇编代码

CDriveClass d;
002613DE  push        1  
002613E0  lea         ecx,[d]  
002613E3  call        CDriveClass::CDriveClass (261136h)