Using dbx to Locate Floating-Point Exceptions

You need to do two things. First, to stop the process whenever an FP exception occurs, type:

(dbx) catch FPE

Next, add the following to your Fortran application:

integer ieeer, ieee_handler, myhandler
ieeer = ieee_handler('set', 'all', myhandler)
...
        
integer function myhandler(sig, code, context)
integer sig, code(5)
call abort()
end

This is necessary because the ieee software typically sets all errors to be silent (not raising signals). This causes all ieee exceptions to generate a SIGFPE as appropriate, which is probably too much.

You can further tailor which exceptions you see by adjusting the parameters of ieee_handler() or by using an alternative to the dbx catch command:

stop sig FPE

which acts just like catch FPE, or

stop sig FPE subcode

For finer control, subcode can be one of the following:

Note that stop and catch are independent and that if you use stop FPE you should also ignore FPE.