带有 QWidget 的分段错误构造函数。 Qt/C++

Question

I have this problem. Sometimes (but very rarely) my program crash on starting. The QDebugger points to the segmentation fault originating from this code:

view_add_bagagli::view_add_bagagli(QWidget*parent):QWidget(parent),setBagWid(new QWidget_add_lug(this)),
setPropWid(new QWidget_add_owner(this)),
setViaWid(new QWidget_add_travel(this)){} // segm fault at this line

And this is the code of QWidget_add_travel 's constructor:

QWidget_add_travel::QWidget_add_travel(QWidget *parent) : Qwidget(parent),via_l(new QVBoxLayout()){
    setLayout(via_l);
    build();
}

But QDebugger did NOT indicate segmentation faults in this code. The strangest thing is the segmentation fault happens sometimes (very rarely) and NOT every time! Maybe this is not a good question, but I am very confused about this error.

Answer 1

You are not calling the QWidget constructor in your constructor (I'm assuming QWidget is the superclass of QWidget_add_travel ). Because the superclass's constructor is not called, the data allocated on the heap for your widget is in an undefined state , ie sooner or later something breaks.

Here's a fixed version:

QWidget_add_travel::QWidget_add_travel(QWidget *parent) 
        : QWidget(parent), via_l(new QVBoxLayout(this))
{
    build();
}

I also took the liberty of simplifying your layout construction by passing this to the layout constructor.