Example: Locate an exception (print address) and abort:
demo% cat LocExcHan.F #include "floatingpoint.h" EXTERNAL Exhandler INTEGER Exhandler, i, ieee_handler REAL:: r = 14.2 , s = 0.0 , t C Detect division by zero i = ieee_handler( ’set’, ’division’, Exhandler ) t = r/s END INTEGER FUNCTION Exhandler( sig, sip, uap) INTEGER sig STRUCTURE /fault/ INTEGER address END STRUCTURE STRUCTURE /siginfo/ INTEGER si_signo INTEGER si_code INTEGER si_errno RECORD /fault/ fault END STRUCTURE RECORD /siginfo/ sip WRITE (*,10) sip.si_signo, sip.si_code, sip.fault.address 10 FORMAT(’Signal ’,i4,’ code ’,i4,’ at hex address ’, Z8 ) Exhandler=1 CALL abort() END demo% f95 -g LocExcHan.F demo% a.out Signal 8 code 3 at hex address 11230 Abort demo% |
In 64–bit SPARC environments, replace the INTEGER declarations within each STRUCTURE with INTEGER*8, and the i4 formats with i8. (Note that this example relies on extensions to the f95 compiler to accept VAX Fortran STRUCTURE statements.)
In most cases, knowing the actual address of the exception is of little use, except with dbx:
demo% dbx a.out (dbx) stopi at 0x11230 Set breakpoint at address (2) stopi at &MAIN+0x68 (dbx) run Run program Running: a.out (process id 18803) stopped in MAIN at 0x11230 MAIN+0x68: fdivs %f3, %f2, %f2 (dbx) where Shows the line number of the exception =>[1] MAIN(), line 7 in "LocExcHan.F" (dbx) list 7 Displays the source code line 7 t = r/s (dbx) cont Continue after breakpoint, enter handler routine Signal 8 code 3 at hex address 11230 abort: called signal ABRT (Abort) in _kill at 0xef6e18a4 _kill+0x8: bgeu _kill+0x30 Current function is exhandler 24 CALL abort() (dbx) quit demo% |
Of course, there are easier ways to determine the source line that caused the error. However, this example does serve to show the basics of exception handling.