### _fpreset -- Reset Floating-Point Unit

Format

>     #include <float.h>
>     void _fpreset(void);

Language Level: Extension
_fpreset resets the floating-point unit to the default state that the math library requires to function correctly. The value of this default state may change between releases of this product. You can determine the default state by calling _fpreset and then calling _control87 with 0 as the parameter.

This function is often used within signal handlers. If a program traps floating-point error signals (SIGFPE) with signal, the program can safely recover from floating-point errors by calling longjmp.

_fpreset resets the floating-point unit of the current thread only. It does not affect any other threads that may be processing.

Return Value
There is no return value.

Example
This example establishes the function fphandler as a floating-point error handler. The main program produces a floating-point error, which causes control to be passed to fphandler. The fphandler function calls _fpreset to reset the floating-point unit, and then returns to main.

    #include <stdio.h>
    #include <stdlib.h>
    #include <signal.h>
    #include <setjmp.h>
    #include <float.h>

    jmp_buf mark;

    void fphandler(int sig)
    {
       printf("Floating point signal = %d\n", sig);
       _fpreset();                /* Reinitialize floating-point package */
       longjmp(mark, -1);
    }

    int main(void)
    {
       double a = 1.0,b = 0.0,c;

       if (SIG_ERR == signal(SIGFPE, (_SigFunc)fphandler))
          return EXIT_FAILURE;
       if (0 == setjmp(mark)) {
          c = a/b;                      /* generate floating-point error */
          printf("Should never get here\n");
       }
       printf("Recovered from floating-point error\n");
       return 0;

       /*******************************************************************
          The output should be:

          Floating point signal = 3
          Recovered from floating-point error
       *******************************************************************/
    }

_clear87 -- Clear Floating-Point Status Word
_control87 -- Set Floating-Point Control Word
longjump -- Restore Stack Environment
signal -- Handle Interrupt Signals
_status87 -- Get Floating-Point Status Word
<float.h>
Exception Handling for Floating-Point Exceptions