Trump campaign backtracks claim that he bought a Glock handgun in South Carolina after it became clear that would be illegal

They actually have three internal safeties: There's the one on the trigger which prevents the trigger from moving backward unless something is inside the trigger guard, is physically on the trigger shoe, and pulling it backward. There's a sort of little shelf on the trigger sear which part of the cruciform slots into which prevents downward movement of the cruciform and keeps it from slipping off the striker and allowing the gun to fire if dropped. Then there's the firing pin safety plunger, which prevents the firing pin/striker from moving forward until the plunger is depressed by a protrusion on the trigger bar when the trigger is in the pulled position. Which means you have to do something monumentally stupid and reckless to shoot yourself in the foot.