FPGETROUND(3)          FreeBSD Library Functions Manual          FPGETROUND(3)

NAME
     fpgetround, fpsetround, fpsetprec, fpgetprec, fpgetmask, fpsetmask,
     fpgetsticky, fpresetsticky - IEEE floating point interface

SYNOPSIS
     #include <ieeefp.h>

     typedef enum {
             FP_RN,          /* round to nearest */
             FP_RM,          /* round down to minus infinity */
             FP_RP,          /* round up to plus infinity */
             FP_RZ           /* truncate */
     } fp_rnd_t;
     fp_rnd_t
     fpgetround(void);

     fp_rnd_t
     fpsetround(fp_rnd_t direction);

     typedef enum {
             FP_PS,          /* 24 bit (single-precision) */
             FP_PRS,         /* reserved */
             FP_PD,          /* 53 bit (double-precision) */
             FP_PE           /* 64 bit (extended-precision) */
     } fp_prec_t;
     fp_prec_t
     fpgetprec(void);

     fp_prec_t
     fpsetprec(fp_prec_t precision);

     #define fp_except_t     int
     #define FP_X_INV        0x01    /* invalid operation */
     #define FP_X_DNML       0x02    /* denormal */
     #define FP_X_DZ         0x04    /* zero divide */
     #define FP_X_OFL        0x08    /* overflow */
     #define FP_X_UFL        0x10    /* underflow */
     #define FP_X_IMP        0x20    /* (im)precision */
     #define FP_X_STK        0x40    /* stack fault */
     fp_except_t
     fpgetmask(void);

     fp_except_t
     fpsetmask(fp_except_t mask);

     fp_except_t
     fpgetsticky(void);

     fp_except_t
     fpresetsticky(fp_except_t sticky);

DESCRIPTION
     The routines described herein are deprecated.  New code should use the
     functionality provided by fenv(3).

     When a floating point exception is detected, the exception sticky flag is
     set and the exception mask is tested.  If the mask is set, then a trap
     occurs.  These routines allow both setting the floating point exception
     masks, and resetting the exception sticky flags after an exception is
     detected.  In addition, they allow setting the floating point rounding
     mode and precision.

     The fpgetround() function returns the current floating point rounding
     mode.

     The fpsetround() function sets the floating point rounding mode and
     returns the previous mode.

     The fpgetprec() function returns the current floating point precision.

     The fpsetprec() function sets the floating point precision and returns
     the previous precision.

     The fpgetmask() function returns the current floating point exception
     masks.

     The fpsetmask() function sets the floating point exception masks and
     returns the previous masks.

     The fpgetsticky() function returns the current floating point sticky
     flags.

     The fpresetsticky() function clears the floating point sticky flags and
     returns the previous flags.

     Sample code which prevents a trap on divide-by-zero:

           fpsetmask(~FP_X_DZ);
           a = 1.0;
           b = 0;
           c = a / b;
           fpresetsticky(FP_X_DZ);
           fpsetmask(FP_X_DZ);

IMPLEMENTATION NOTES
     The fpgetprec() and fpsetprec() functions provide functionality
     unavailable on many platforms.  At present, they are implemented only on
     the i386 and amd64 platforms.  Changing precision is not a supported
     feature: it may be ineffective when code is compiled to take advantage of
     SSE, and many library functions and compiler optimizations depend upon
     the default precision for correct behavior.

SEE ALSO
     fenv(3), isnan(3)

HISTORY
     These routines are based on SysV/386 routines of the same name.

CAVEATS
     After a floating point exception and before a mask is set, the sticky
     flags must be reset.  If another exception occurs before the sticky flags
     are reset, then a wrong exception type may be signaled.

FreeBSD 13.1-RELEASE-p6        December 3, 2010        FreeBSD 13.1-RELEASE-p6