构造函数与重载构造函数

发现slam程序里有个这种写法,在mappoint.h中写的如下

    MapPoint() {}
    // XXX:重载构造函数,一个默认(new的时候用),一个含参
    MapPoint(long id, Vec3 position);

在mappoint.cpp中有含参构造函数的定义:

MapPoint::MapPoint(long id, Vec3 position) : id_(id), pos_(position) {}

 这个涉及到new关键字的默认构造函数与构造函数的重载,具体看链接:

https://www.cnblogs.com/lykkk/p/10626335.html#:~:text=%20%E6%9E%84%E9%80%A0%E5%87%BD%E6%95%B0%E6%98%AF%E5%8F%AF%E4%BB%A5%E9%87%8D%E8%BD%BD%E7%9A%84%EF%BC%8C%E5%8D%B3%E5%86%99%E5%A4%9A%E4%B8%AA%E6%9E%84%E9%80%A0%E5%87%BD%E6%95%B0%EF%BC%8C%E5%AE%83%E4%BB%AC%E5%85%B7%E6%9C%89%E4%B8%8D%E5%90%8C%E7%9A%84%E5%8F%82%E6%95%B0%E8%A1%A8%E5%92%8C%E7%9B%B8%E5%90%8C%E7%9A%84%E5%90%8D%E7%A7%B0%EF%BC%8C%E5%A6%82%E6%9E%9C%E6%B2%A1%E6%9C%89%E5%8F%82%E6%95%B0%E4%BF%A1%E6%81%AF%EF%BC%8C%E7%BC%96%E8%AF%91%E5%99%A8%E5%B0%B1%E8%AE%A4%E4%B8%BA%E8%B0%83%E7%94%A8%E9%BB%98%E8%AE%A4%E6%9E%84%E9%80%A0%E5%87%BD%E6%95%B0%E3%80%82%20%E7%89%B9%E7%82%B9,%E9%87%8D%E8%BD%BD%E6%9E%84%E9%80%A0%E5%87%BD%E6%95%B0%E5%85%B7%E6%9C%89%E4%B8%8D%E5%90%8C%E7%9A%84%E5%8F%82%E6%95%B0%E8%A1%A8%E5%92%8C%E7%9B%B8%E5%90%8C%E7%9A%84%E5%90%8D%E7%A7%B0%20%E6%A0%B9%E6%8D%AE%E4%BC%A0%E5%8F%82%E4%B8%AA%E6%95%B0%E5%86%B3%E5%AE%9A%E8%B0%83%E7%94%A8%E5%93%AA%E4%B8%AA%E6%9E%84%E9%80%A0%E5%87%BD%E6%95%B0%20%E5%88%9B%E5%BB%BA%E5%AF%B9%E8%B1%A1%E6%97%B6%E8%A6%81%E4%BC%A0%E5%8F%82%E6%95%B0%E8%AE%A9%E7%BC%96%E8%AF%91%E5%99%A8%E7%9F%A5%E9%81%93%E8%B0%83%E7%94%A8%E5%93%AA%E4%B8%AA%E6%9E%84%E9%80%A0%E5%87%BD%E6%95%B0