1.\" Copyright (c) 1993 Andrew Moore, Talke Studio 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)fpgetround.3 1.0 (Berkeley) 9/23/93 33.\" $FreeBSD$ 34.\" 35.Dd August 23, 1993 36.Dt FPGETROUND 3 37.Os 38.Sh NAME 39.Nm fpgetround , 40.Nm fpsetround , 41.Nm fpsetprec , 42.Nm fpgetprec , 43.Nm fpgetmask , 44.Nm fpsetmask , 45.Nm fpgetsticky , 46.Nm fpresetsticky 47.Nd IEEE floating point interface 48.Sh SYNOPSIS 49.Fd #include <ieeefp.h> 50.Ft typedef enum { 51.br 52.Fa FP_RN, 53.Li /* round to nearest */ 54.br 55.Fa FP_RM, 56.Li /* round to minus infinity */ 57.br 58.Fa FP_RP, 59.Li /* round to plus infinity */ 60.br 61.Fa FP_RZ, 62.Li /* truncate */ 63.br 64.Ft } fp_rnd_t; 65.Pp 66.Ft fp_rnd_t 67.Fn fpgetround void 68.Ft fp_rnd_t 69.Fn fpsetround "fp_rnd_t direction" 70.Pp 71.nr fZ 0 72.Ft typedef enum { 73.br 74.Fa FP_PS, 75.Li /* 24 bit (single-precision) */ 76.br 77.Fa FP_PRS, 78.Li /* reserved */ 79.br 80.Fa FP_PD, 81.Li /* 53 bit (double-precision) */ 82.br 83.Fa FP_PE, 84.Li /* 64 bit (extended-precision) */ 85.br 86.Ft } fp_prec_t; 87.Pp 88.Ft fp_prec_t 89.Fn fpgetprec void 90.Ft fp_prec_t 91.Fn fpsetprec "fp_prec_t precision" 92.Pp 93.Fd #define fp_except_t int 94.Fd #define FP_X_INV 0x01 /* invalid */ 95.Fd #define FP_X_OFL 0x08 /* overflow */ 96.Fd #define FP_X_UFL 0x10 /* underflow */ 97.Fd #define FP_X_DZ 0x04 /* divide-by-zero */ 98.Fd #define FP_X_IMP 0x20 /* loss of precision */ 99.Fd #define FP_X_DNML 0x02 /* denormal */ 100.Ft fp_except_t 101.Fn fpgetmask void 102.Ft fp_except_t 103.Fn fpsetmask "fp_except_t mask" 104.Ft fp_except_t 105.Fn fpgetsticky void 106.Ft fp_except_t 107.Fn fpresetsticky "fp_except_t sticky" 108.Sh DESCRIPTION 109When a floating point exception is detected, the exception sticky flag is 110set and the exception mask is tested. 111If the mask is set, then a trap 112occurs. These routines allow both setting the floating point exception 113masks, and resetting the exception sticky flags after an exception is 114detected. In addition, they allow setting the floating point rounding mode 115and precision. 116.Pp 117The 118.Fn fpgetround 119function 120returns the current floating point rounding mode. 121.Pp 122The 123.Fn fpsetround 124function 125sets the floating point rounding mode and returns 126the previous mode. 127.Pp 128The 129.Fn fpgetprec 130function 131returns the current floating point precision. 132.Pp 133The 134.Fn fpsetprec 135function 136sets the floating point precision and returns 137the previous precision. 138.Pp 139The 140.Fn fpgetmask 141function 142returns the current floating point exception masks. 143.Pp 144The 145.Fn fpsetmask 146function 147sets the floating point exception masks and returns the 148previous masks. 149.Pp 150The 151.Fn fpgetsticky 152function 153returns the current floating point sticky flags. 154.Pp 155The 156.Fn fpresetsticky 157function 158clears the floating point sticky flags and returns 159the previous flags. 160.Pp 161Sample code which prevents a trap on divide-by-zero: 162.Bd -literal -offset indent 163fpsetmask(~FP_X_DZ); 164a = 1.0; 165b = 0; 166c = a / b; 167fpresetsticky(FP_X_DZ); 168fpsetmask(FP_X_DZ); 169.Ed 170.Sh SEE ALSO 171.Xr isnan 3 172.Sh CAVEAT 173After a floating point exception and before a mask is set, the sticky 174flags must be reset. If another exception occurs before the sticky 175flags are reset, then a wrong exception type may be signaled. 176.Sh HISTORY 177These routines are based on SysV/386 routines of the same name. 178