The windshield installer would use urethene to seal the windshield and moldings.
If the windshield is leaking, it is not the moldings they are just there to finish the installation cosmetically. The windshield is glued in around the perimeter with urethene adheasive. If there is a leak, you mght try removing the inside A-pillar moldings and re-sealing from the inside (or take it to a windshield installer, it is probably well worth the money to have it sealed).