Running in debug mode (F8) in DevC++ is different than just running the program. It looks like debug mode actually catches errors, because it found one that crashed the program after new tileset was made (in Stile). And gdb knew where the problem was. Way! I really need to run in debug mode more often, even gdb output can be cryptic. It's now complaining something about st_copy, I don't know why. Nothing special going on with st_copy.