GNU Scientific Library – Reference Manual: Handling floating point exceptions

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### A.3 Handling floating point exceptions

It is possible to stop the program whenever a `SIGFPE` floating point exception occurs. This can be useful for finding the cause of an unexpected infinity or `NaN`. The current handler settings can be shown with the command `info signal SIGFPE`.

    (gdb) info signal SIGFPE
    Signal  Stop  Print  Pass to program Description
    SIGFPE  Yes   Yes    Yes             Arithmetic exception

Unless the program uses a signal handler the default setting should be changed so that SIGFPE is not passed to the program, as this would cause it to exit. The command `handle SIGFPE stop nopass` prevents this.

    (gdb) handle SIGFPE stop nopass
    Signal  Stop  Print  Pass to program Description
    SIGFPE  Yes   Yes    No              Arithmetic exception

Depending on the platform it may be necessary to instruct the kernel to generate signals for floating point exceptions. For programs using GSL this can be achieved using the `GSL_IEEE_MODE` environment variable in conjunction with the function `gsl_ieee_env_setup` as described in see IEEE floating-point arithmetic.

    (gdb) set env GSL_IEEE_MODE=double-precision