Initialize floating–point hardware to non–standard preferences.
This option is a macro for the combination of the following option flags:
–fns -ftrap=common
Specifying -fnonstd is approximately equivalent to the following two calls at the beginning of a Fortran main program.
i=ieee_handler("set", "common", SIGFPE_ABORT)
call nonstandard_arithmetic()
The nonstandard_arithmetic() routine replaces the obsolete abrupt_underflow() routine of earlier releases.
To be effective, the main program must be compiled with this option.
Using this option initializes the floating-point hardware to:
Abort (trap) on floating-point exceptions.
Flush underflow results to zero if it will improve speed, rather than produce a subnormal number as the IEEE standard requires.
See -fns for more information about gradual underflow and subnormal numbers.
The -fnonstd option allows hardware traps to be enabled for floating–point overflow, division by zero, and invalid operation exceptions. These are converted into SIGFPE signals, and if the program has no SIGFPE handler, it terminates with a dump of memory.
For more information, see the ieee_handler(3m) and ieee_functions(3m) man pages, the Numerical Computation Guide, and the Fortran Programming Guide.