We are not aware of any particular "code" in Alabama regarding a cracked windshield so if you are looking to see if there are specific laws pertaining to a cracked or broken windshield we would advise you to contact the Alabama Department of Public Safety (DPS).
Alabama Code Title 32, Ch. 5, Article 9 does give information on requirements regarding the equipment of a motor vehicle. Under section 32-5-215 is titled Windshields must be unobstructed and states the following:
(a) No person shall drive any motor vehicle with any sign, poster or other nontransparent material upon the front windshield, sidewings or side or rear windows of such vehicle which obstructs the driver's clear view of the highway or any intersecting highway.
(b) The windshield on every motor vehicle shall be equipped with a device for cleaning rain, snow or other moisture from the windshield, which device shall be so constructed as to be controlled or operated by the driver of the vehicle.
(c) Every windshield wiper upon a motor vehicle shall be maintained in good working order.
(d) No person shall operate a motor vehicle which has a windshield, sidewing or rear window which has tinting to the extent or manufactured in such a way that occupants of the vehicle cannot be easily identified or recognized through the sidewing or rear windows from outside the motor vehicle.
(e) The provisions of this section shall not apply to the manufactured tinting of windshields of motor vehicles or to certificates of identification, decals or other papers required by law to be displayed on such windshield or windows.
It does not appear this section of Alabama law mentions cracks being an issue with windshield. Since we are not lawyers we are not familiar with every aspect of AL laws so would advise you to check with the AL DPS, Motor Vehicle Division or a lawyer that works with this type of law in Alabama.
If your windshield has a crack in it that is impairing your vision as a driver you should get it repaired so it does not harm your ability to drive. If you have comprehensive coverage on your vehicle you can make a claim for the windshield repair or replacement. The deductible associated with this portion of your auto insurance's physical damage coverage would be due to have the windshield repair (or replacement) done.