The f$CHECKPOINTERg directive turns heap pointer checking on (value ON) or o (value OFF). When heap pointer checking is on and the code is compiled with the -gh (heaptrace) option on, then a check is inserted when dereferencing a pointer. The check will verify that the pointer contains a valid value, i.e. points to a location that is reachable by the program: the stack or a location in the heap. If not, a run-time error 216 or 204 is raised.
If the code is compiled without -gl switch, then this directive has no e ect. Note that this considerably slows down the code.