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 ex

ception 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 function

ality unavailable on many platforms. At present, they are implemented

only on the
i386 and amd64 platforms.

SEE ALSO

fenv(3), isnan(3)

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.

HISTORY

These routines are based on SysV/386 routines of the same

name.

BSD August 23, 1993

BSD