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Dd March 26, 2011
Dt FPGETMASK 3
Os
Sh NAME
Nm fpgetmask ,
Nm fpgetprec ,
Nm fpgetround ,
Nm fpgetsticky ,
Nm fpsetmask ,
Nm fpsetprec ,
Nm fpsetround ,
Nm fpsetsticky
Nd IEEE FP mode control
Sh LIBRARY
Lb libc
Sh SYNOPSIS
In ieeefp.h
Ft fp_except_t
Fn fpgetmask void
Ft fp_prec_t
Fn fpgetprec void
Ft fp_rnd_t
Fn fpgetround void
Ft fp_except_t
Fn fpgetsticky void
Ft fp_except_t
Fn fpsetmask "fp_except_t mask"
Ft fp_prec_t
Fn fpsetprec "fp_prec_t prec"
Ft fp_rnd_t
Fn fpsetround "fp_rnd_t rnd_dir"
Ft fp_except_t
Fn fpsetsticky "fp_except_t sticky"
Sh DESCRIPTION
A rounding mode
Ft fp_rnd_t
is one of:
Bl -column -offset indent FP_RZ
It Dv FP_RZ Ta rounding towards Em zero
It Dv FP_RM Ta rounding down to Pq Em Minus infinity
It Dv FP_RN Ta rounding to Em nearest
It Dv FP_RP Ta rounding down to Pq Em Plus infinity
El
The default mode is
Dv FP_RN .
Pp
An
Ft fp_except_t
value is a bitmask specifying an exception type and containing any of
the values listed below.
Bl -column -offset indent FP_X_UFLxx
It Dv FP_X_INV Ta Invalid\ Operation
It Dv FP_X_DZ Ta Division\ by\ zero
It Dv FP_X_OFL Ta Overflow
It Dv FP_X_UFL Ta Underflow
It Dv FP_X_IMP Ta Imprecision (inexact)
It Dv FP_X_IOV Ta Integer\ Overflow
El
Pp
An
Ft fp_prec_t
specifies the precision of the floating point operations listed below.
Bl -column -offset indent FP_RPS
It Dv FP_PS Ta Dv 24 bit (single-precision)
It Dv FP_PRS Ta reserved
It Dv FP_PD Ta Dv 53 bit (double-precision)
It Dv FP_PE Ta Dv 64 bit (extended-precision)
El
Pp
The
Fn fpsetmask
function will set the current exception mask, i.e., it will cause
future operations with the specified result status to raise the
Dv SIGFPE
exception.
The
Fn fpgetmask
function will return the current exception mask.
Pp
The
Fn fpgetprec
function will return the current floating point precision.
The
Fn fpsetprec
function will set the floating point precision and will return
the previous precision.
Pp
The
Fn fpsetround
function will cause future operations to use the specified dynamic
rounding mode.
The
Fn fpgetround
function will return the current rounding mode.
Bl -tag -width Note:x
It Em 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.
El
Pp
A
Dq 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
Dv SIGFPE
is generated.
The
Fn fpsetsticky
function will set or clear the specified exception history bits.
The
Fn fpgetsticky
function will return the exception history bits.
Sh RETURN VALUES
The
Fn fpgetround
and
Fn fpsetround
functions return the
Pq previous
rounding mode.
The
Fn fpgetmask ,
Fn fpsetmask ,
Fn fpgetsticky ,
and
Fn fpsetsticky
functions return the
Pq previous
exception mask and exception history bits.
Sh SEE ALSO
Xr sigaction 2 ,
Xr fenv 3
Sh 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
Xr fenv 3
should be used, although the interfaces in
Xr fenv 3
don't support getting or setting the precision.

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