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. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)fpgetround.3 1.0 (Berkeley) 9/23/93 29.\" $FreeBSD: src/share/man/man3/fpgetround.3,v 1.20 2013/04/12 00:37:30 svnexp Exp $ 30.\" 31.Dd July 14, 2013 32.Dt FPGETROUND 3 33.Os 34.Sh NAME 35.Nm fpgetround , 36.Nm fpsetround , 37.Nm fpsetprec , 38.Nm fpgetprec , 39.Nm fpgetmask , 40.Nm fpsetmask , 41.Nm fpgetsticky , 42.Nm fpresetsticky 43.Nd IEEE floating point interface 44.Sh LIBRARY 45.Lb libc 46.Sh SYNOPSIS 47.In ieeefp.h 48.Bd -literal 49typedef enum { 50 FP_RN, /* round to nearest */ 51 FP_RM, /* round down to minus infinity */ 52 FP_RP, /* round up to plus infinity */ 53 FP_RZ /* truncate */ 54} fp_rnd_t; 55.Ed 56.Ft fp_rnd_t 57.Fn fpgetround void 58.Ft fp_rnd_t 59.Fn fpsetround "fp_rnd_t direction" 60.Bd -literal 61typedef enum { 62 FP_PS, /* 24 bit (single-precision) */ 63 FP_PRS, /* reserved */ 64 FP_PD, /* 53 bit (double-precision) */ 65 FP_PE /* 64 bit (extended-precision) */ 66} fp_prec_t; 67.Ed 68.Ft fp_prec_t 69.Fn fpgetprec void 70.Ft fp_prec_t 71.Fn fpsetprec "fp_prec_t precision" 72.Bd -literal 73#define fp_except_t int 74#define FP_X_INV 0x01 /* invalid operation */ 75#define FP_X_DNML 0x02 /* denormal */ 76#define FP_X_DZ 0x04 /* zero divide */ 77#define FP_X_OFL 0x08 /* overflow */ 78#define FP_X_UFL 0x10 /* underflow */ 79#define FP_X_IMP 0x20 /* (im)precision */ 80#define FP_X_STK 0x40 /* stack fault */ 81.Ed 82.Ft fp_except_t 83.Fn fpgetmask void 84.Ft fp_except_t 85.Fn fpsetmask "fp_except_t mask" 86.Ft fp_except_t 87.Fn fpgetsticky void 88.Ft fp_except_t 89.Fn fpresetsticky "fp_except_t sticky" 90.Sh DESCRIPTION 91The routines described herein are deprecated. 92New code should use the functionality provided by 93.Xr fenv 3 . 94.Pp 95When a floating point exception is detected, the exception sticky flag is 96set and the exception mask is tested. 97If the mask is set, then a trap occurs. 98These routines allow both setting the floating point exception 99masks, and resetting the exception sticky flags after an exception is 100detected. 101In addition, they allow setting the floating point rounding mode 102and precision. 103.Pp 104The 105.Fn fpgetround 106function 107returns the current floating point rounding mode. 108.Pp 109The 110.Fn fpsetround 111function 112sets the floating point rounding mode and returns 113the previous mode. 114.Pp 115The 116.Fn fpgetprec 117function 118returns the current floating point precision. 119.Pp 120The 121.Fn fpsetprec 122function 123sets the floating point precision and returns 124the previous precision. 125.Pp 126The 127.Fn fpgetmask 128function 129returns the current floating point exception masks. 130.Pp 131The 132.Fn fpsetmask 133function 134sets the floating point exception masks and returns the 135previous masks. 136.Pp 137The 138.Fn fpgetsticky 139function 140returns the current floating point sticky flags. 141.Pp 142The 143.Fn fpresetsticky 144function 145clears the floating point sticky flags and returns 146the previous flags. 147.Pp 148Sample code which prevents a trap on divide-by-zero: 149.Bd -literal -offset indent 150fpsetmask(~FP_X_DZ); 151a = 1.0; 152b = 0; 153c = a / b; 154fpresetsticky(FP_X_DZ); 155fpsetmask(FP_X_DZ); 156.Ed 157.Sh IMPLEMENTATION NOTES 158The 159.Fn fpgetprec 160and 161.Fn fpsetprec 162functions provide functionality unavailable on many platforms. 163At present, they are implemented only on the i386 and x86_64 platforms. 164Changing precision is not a supported feature: 165it may be ineffective when code is compiled to take advantage of SSE, 166and many library functions and compiler optimizations depend upon the 167default precision for correct behavior. 168.Sh SEE ALSO 169.Xr fenv 3 , 170.Xr isnan 3 171.Sh HISTORY 172These routines are based on SysV/386 routines of the same name. 173.Sh CAVEATS 174After a floating point exception and before a mask is set, the sticky 175flags must be reset. 176If another exception occurs before the sticky 177flags are reset, then a wrong exception type may be signaled. 178