C++系統本身主動生成默認構造函數的狀況

(1) 基類存在默認構造函數

class CBaseClass
{
public:

CBaseClass()
{
m_i = 0;
}

private:

int m_i;
};


class CDriveClass: public CBaseClass
{
public:

void func()
{
}

private:

};

(2) 成員變量存在默認構造函數

class CTestClass
{
public:

CTestClass()
{
m_i = 1;
}

private:

int m_i;
};

class CDriveClass
{
public:
 void func()
{
}

private:

CTestClass mTestClass;
};

(3) 存在虛函數：初始化虛函數指針

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

 void func()
{
}

};

(4) 存在虛基類：初始化虛基類指針

class CBaseClass
{
};


class CDriveClass: virtual public CBaseClass
{
public:

void func()
{
}
};

詳細可以查看反彙編代碼：Visual Stdio 2010編譯器中：Debug->windows->Disassembly

--彙編代碼

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