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 December 3, 2010 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.In ieeefp.h 50.Bd -literal 51typedef enum { 52 FP_RN, /* round to nearest */ 53 FP_RM, /* round down to minus infinity */ 54 FP_RP, /* round up to plus infinity */ 55 FP_RZ /* truncate */ 56} fp_rnd_t; 57.Ed 58.Ft fp_rnd_t 59.Fn fpgetround void 60.Ft fp_rnd_t 61.Fn fpsetround "fp_rnd_t direction" 62.Bd -literal 63typedef enum { 64 FP_PS, /* 24 bit (single-precision) */ 65 FP_PRS, /* reserved */ 66 FP_PD, /* 53 bit (double-precision) */ 67 FP_PE /* 64 bit (extended-precision) */ 68} fp_prec_t; 69.Ed 70.Ft fp_prec_t 71.Fn fpgetprec void 72.Ft fp_prec_t 73.Fn fpsetprec "fp_prec_t precision" 74.Bd -literal 75#define fp_except_t int 76#define FP_X_INV 0x01 /* invalid operation */ 77#define FP_X_DNML 0x02 /* denormal */ 78#define FP_X_DZ 0x04 /* zero divide */ 79#define FP_X_OFL 0x08 /* overflow */ 80#define FP_X_UFL 0x10 /* underflow */ 81#define FP_X_IMP 0x20 /* (im)precision */ 82#define FP_X_STK 0x40 /* stack fault */ 83.Ed 84.Ft fp_except_t 85.Fn fpgetmask void 86.Ft fp_except_t 87.Fn fpsetmask "fp_except_t mask" 88.Ft fp_except_t 89.Fn fpgetsticky void 90.Ft fp_except_t 91.Fn fpresetsticky "fp_except_t sticky" 92.Sh DESCRIPTION 93The routines described herein are deprecated. 94New code should use the functionality provided by 95.Xr fenv 3 . 96.Pp 97When a floating point exception is detected, the exception sticky flag is 98set and the exception mask is tested. 99If the mask is set, then a trap 100occurs. 101These routines allow both setting the floating point exception 102masks, and resetting the exception sticky flags after an exception is 103detected. 104In addition, they allow setting the floating point rounding mode 105and precision. 106.Pp 107The 108.Fn fpgetround 109function 110returns the current floating point rounding mode. 111.Pp 112The 113.Fn fpsetround 114function 115sets the floating point rounding mode and returns 116the previous mode. 117.Pp 118The 119.Fn fpgetprec 120function 121returns the current floating point precision. 122.Pp 123The 124.Fn fpsetprec 125function 126sets the floating point precision and returns 127the previous precision. 128.Pp 129The 130.Fn fpgetmask 131function 132returns the current floating point exception masks. 133.Pp 134The 135.Fn fpsetmask 136function 137sets the floating point exception masks and returns the 138previous masks. 139.Pp 140The 141.Fn fpgetsticky 142function 143returns the current floating point sticky flags. 144.Pp 145The 146.Fn fpresetsticky 147function 148clears the floating point sticky flags and returns 149the previous flags. 150.Pp 151Sample code which prevents a trap on divide-by-zero: 152.Bd -literal -offset indent 153fpsetmask(~FP_X_DZ); 154a = 1.0; 155b = 0; 156c = a / b; 157fpresetsticky(FP_X_DZ); 158fpsetmask(FP_X_DZ); 159.Ed 160.Sh IMPLEMENTATION NOTES 161The 162.Fn fpgetprec 163and 164.Fn fpsetprec 165functions provide functionality unavailable on many platforms. 166At present, they are implemented only on the i386 and amd64 platforms. 167Changing precision is not a supported feature: 168it may be ineffective when code is compiled to take advantage of SSE, 169and many library functions and compiler optimizations depend upon the 170default precision for correct behavior. 171.Sh SEE ALSO 172.Xr fenv 3 , 173.Xr isnan 3 174.Sh HISTORY 175These routines are based on SysV/386 routines of the same name. 176.Sh CAVEATS 177After a floating point exception and before a mask is set, the sticky 178flags must be reset. 179If another exception occurs before the sticky 180flags are reset, then a wrong exception type may be signaled. 181