Like he said or better known as Stress Crack. You can do the ballpoint pen test at home prior to going to dealer. If the ballpoint stops, it means that's where the impact happened. If you get a smooth ballpen flow from one end of the crack to the other, then you should have a stress crack and covered under warranty. Happened to me with my 2008 CRV.Reply to kevmelbel :-
The dealer will probably produce a ballpoint pen and roll it along the windshield crack to see if he can find the impact spot from road debris. If there is no chip on the outside and it looks like the crack maybe from bad install, I'd be looking for a replacement under warranty.