qt - c++ program crashes when adding new QGraphicsItem to scene -

my c++ program crashes when add new qgraphicslineitem qlist of qgraphicspixmapitem. below function.

void mainwindow::linkcomputernodes(qlist<node*> routers) {      for(int i=0;i<routers.length();i++)     {        scene->additem(new link(routers.at(i),routers.at(i+1)));     }  } 

your loop:

for(int i=0;i<routers.length();i++) 

goes through every single router in list, add link each router router directly after it. means last router, trying add link 1 doesn't exist. try changing loop to:

for(int i=0;i<routers.length() - 1;i++) 

so add links between existing routers.