If you read the Glock literature, Gaston claims 3 safeties. I don't know that I can completely agree with that, but I have a couple Glocks, and have made the transition from 1911A1 pattern sidearms. The key is to, as one poster on here put it, "Keep your booger hook out of the fire house"
The gun WILL NOT go off unless the trigger is pressed. I have fussed and putzed with mine in every conceivable way to see if it might drop the hammer without my "permission"
I have not found a way for that to happen.
I now carry one of my Glocks either OC or CC with confidence that if I do my part, it will do its part.
There are aftermarket devices you can buy if you want a "safety". It blocks the trigger so it won't go backward.
Ask around, try one. Once you get used to a 1/2" trigger pull, it's a good gun.