C++默认构造函数

//正确
class Second : public QObject
{
    Q_OBJECT
public:
    Second();
    explicit Second(QObject *parent,int num);

    bool testFucntion(void);
signals:

public slots:

//错误，原因-声明中，参数都是带默认值的，那样编译器无法和默认构造函数区分开 
class Second : public QObject
{
    Q_OBJECT
public:
    Second();
    explicit Second(QObject *parent=0,int num);

    bool testFucntion(void);
signals:

public slots:

//正确
class Second : public QObject
{
    Q_OBJECT
public:
    Second();
    explicit Second(QObject *parent，int num=0);

    bool testFucntion(void);
signals:

public slots:

参看链接：

http://bbs.csdn.net/topics/360187259