Depends on the location. "Star" cracks are damage from rocks/stones flying off of the tires from underneath the fenderwell. Mostly only occur on the tops of the fenders, but can also be seen on the sides. The best defense against that is a good undercoating....which is the main reason GM did it to begin with. To fix this, it needs to be sanded down to the glass, epoxied/resined, gelcoated, and painted.
Stress cracks in the 'glass are common. The only real "fix" is a sanding down to the bare glass, a gel coat, and paint.
Cracks in the paint can only be fixed by sanding the cracks out, and repainting.
Sometimes, a small paint crack can be lightly sanded, and buffed out, but it's NOT a "fix"...just a band-aid.
______________
Joel Adams
C3VR Lifetime Member #56
My Link
(click for Texas-sized view!) NCRS
"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"