FPGETMASK(3)

FPGETMASK(3) | NetBSD Library Functions Manual | FPGETMASK(3)

# NAME

fpgetmask, fpgetprec, fpgetround, fpgetsticky, fpsetmask, fpsetprec, fpsetround, fpsetsticky — IEEE FP mode control

# LIBRARY

Standard C Library (libc, -lc)

# SYNOPSIS

#include <ieeefp.h>

fp_except_t
fpgetmask(void);

fp_prec_t
fpgetprec(void);

fp_rnd_t
fpgetround(void);

fp_except_t
fpgetsticky(void);

fp_except_t
fpsetmask(fp_except_t mask);

fp_prec_t
fpsetprec(fp_prec_t prec);

fp_rnd_t
fpsetround(fp_rnd_t rnd_dir);

fp_except_t
fpsetsticky(fp_except_t sticky);

# DESCRIPTION

A rounding mode fp_rnd_t is one of:

FP_RZ | rounding towards zero
FP_RM | rounding down to (Minus infinity)
FP_RN | rounding to nearest
FP_RP | rounding down to (Plus infinity)

The default mode is FP_RN.

An fp_except_t value is a bitmask specifying an exception type and containing any of the values listed below.

FP_X_INV | Invalid Operation
FP_X_DZ | Division by zero
FP_X_OFL | Overflow
FP_X_UFL | Underflow
FP_X_IMP | Imprecision (inexact)
FP_X_IOV | Integer Overflow

An fp_prec_t specifies the precision of the floating point operations listed below.

FP_PS | 24 bit (single-precision)
FP_PRS | reserved
FP_PD | 53 bit (double-precision)
FP_PE | 64 bit (extended-precision)

The fpsetmask() function will set the current exception mask, i.e., it will cause future operations with the specified result status to raise the SIGFPE exception. The fpgetmask() function will return the current exception mask.

The fpgetprec() function will return the current floating point precision. The fpsetprec() function will set the floating point precision and will return the previous precision.

The fpsetround() function will cause future operations to use the specified dynamic rounding mode. The fpgetround() function will return the current rounding mode.

Note:
  On some architectures, instructions can optionally specify static rounding modes and exception enables that will supersede the specified dynamic mode. On other architectures, these features may not be fully supported.

A “sticky” status word may be maintained in which a bit is set every time an exceptional floating point condition is encountered, whether or not a SIGFPE is generated. The fpsetsticky() function will set or clear the specified exception history bits. The fpgetsticky() function will return the exception history bits.

# RETURN VALUES

The fpgetround() and fpsetround() functions return the (previous) rounding mode. The fpgetmask(), fpsetmask(), fpgetsticky(), and fpsetsticky() functions return the (previous) exception mask and exception history bits.

# SEE ALSO

sigaction(2), fenv(3)

# BUGS

There is no way to return an unsupported value. Not all processors support all the modes. These interfaces are deprecated and the ones in fenv(3) should be used, although the interfaces in fenv(3) don't support getting or setting the precision.

March 26, 2011 | NetBSD 5.99