I think there are essentially two problems possible with pointers: (a) Uninitialized pointer (i.e. neither NULL nor associated) (b) Using an unassociated pointer
I think checking (a) is not easily doable as one would need to pass this status (has been initialized? yes/no) on to subroutines. (NAG f95 does so, but one needs to compile all parts of the program with this option as the variable status is passed on to the subroutines. This -C=uninitialized options is still great to find uninitialized variables, esp. those (e.g. integer) which can not be pre-autoinitialized by NaN.) Thus this is a request for enhancement for the second type. Example: program pointtest implicit none real, pointer :: r nullify(r) call foo(r) ! Error one r = 5.0 ! Error two contains subroutine foo(bar) real, target, intent(in) :: bar ! The error occures already here and not in the next line! print *, bar end subroutine foo end program pointtest Both are caught by NAG f95 with -C=pointer and by ifort with -check pointer: Reference to disassociated POINTER R and forrtl: severe (408): fort: (7): Attempt to use pointer R when it is not associated with a target However, the error analysis could be improved for both: Ifort gives a trace, but even with "-g" it does not show where. NAG at least coredumps and thus one can find out where it crashes: gdb -> bt ... #3 0x00002af4962e5e1a in __NAGf90_badptr1 () from /opt/nag/lib/libf98.so.1 #4 0x0000000000403338 in main (argc=1, argv=0x7fff14a00578) at pointest.f90:6 We should try to find something, which is easily debuggable (e.g. spitting out the file and line number?). If we say that the user should use gdb himself [as we used to with boundary check], then we should at least tell, were to set the break point [unless we coredump, the one can use "bt"]. At least I didn't found it obvious to set a break point at "exit__" (or something like that), which was also in a library not loaded when loading the program in gdb. Well, fortunally -fbounds-check now prints file and line :-) (The two pointer tests of Polyhedron's diagnotic check, by the way, only the first type.) -- Summary: Run-time check using nullified pointers Product: gcc Version: 4.3.0 Status: UNCONFIRMED Severity: enhancement Priority: P3 Component: fortran AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: tobias dot burnus at physik dot fu-berlin dot de http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29616