FPGETMASK(3) BSD 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 con‐
taining 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 preci‐
sion. 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 speci‐
fied 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) round‐
ing mode. The fpgetmask(), fpsetmask(), fpgetsticky(), and fpsetsticky()
functions return the (previous) exception mask and exception history
bits.
SEE ALSOsigaction(2), fenv(3)BUGS
There is no way to return an unsupported value. Not all processors sup‐
port 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.
BSD March 26, 2011 BSD
