As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AT CRUISE, FL400, AT MAXIMUM DIFFERENCE A BANG WAS HEARD AND THE CAPTAIN'S WINDSHIELD CRACKED ALL OVER . IT APPEARS TO BE THE OUTER PANEL. ECAM MSG 'A ICE L WSHLD HEAT'. MAINTENANCE REPLACED THE WINDOW HEAT COMPUTER AND THE CAPTAIN'S WINDSHIELD.