Installing an exception handler

By default, programs on AIX do not trap on floating-point exceptions unless a signal handler is installed. To produce a core file, you can use the xl__trcedump signal handler described below. If you want to install a SIGTRAP or SIGFPE signal handler, use the -qsigtrap option. It allows you to specify an Open XL Fortran handler that produces a traceback or to specify a handler you have written:

xlf95 -qflttrap=ov:und:en pi.f                             # Dump core on an exception
xlf95 -qflttrap=ov:und:en -qsigtrap pi.f                   # Uses the xl__trce handler
xlf95 -qflttrap=ov:und:en -qsigtrap=return_22_over_7 pi.f  # Uses any other handler

You can also install an alternative exception handler, either one supplied by Open XL Fortran or one you have written yourself, by calling the SIGNAL subroutine (defined in /usr/include/fexcp.h):

  INCLUDE 'fexcp.h'
  CALL SIGNAL(SIGTRAP,handler_name)
  CALL SIGNAL(SIGFPE,handler_name)

The Open XL Fortran exception handlers and related routines are:

xl__ieee

Produces a traceback and an explanation of the signal and continues execution by supplying the default IEEE result for the failed computation. This handler allows the program to produce the same results as if exception detection was not turned on.

xl__trce

Produces a traceback and stops the program.

xl__trcedump

Produces a traceback and a core file and stops the program.

xl__sigdump

Provides a traceback that starts from the point at which it is called and provides information about the signal. You can only call it from inside a user-written signal handler. It does not stop the program. To successfully continue, the signal handler must perform some cleanup after calling this subprogram.

xl__trbk

Provides a traceback that starts from the point at which it is called. You call it as a subroutine from your code, rather than specifying it with the -qsigtrap option. It requires no parameters. It does not stop the program.