The mag safety on the High-Power in the British army was a common cause of accidents, since the unload drill involved inserting the magazine and pulling the trigger. Guess what the problem was. Two guys were playing the fire a pencil game in a sangar one night, one recocked the hammer, the other racked the slide and put a pencil straight through his colleague, killing him.
All firearms, except maybe the Sten sputter gun have a mechanical device to stop the gun firing by itself, but it is a stretch to call this a "safety" when it is really a sear. I do have a Glock, but I would not want to carry it IWB, even if I could.
I had an antique revolver with a slot in the hammer, and a safety that moved into the slot, a very nice design.