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.\" $FreeBSD$ 30.\" 31.Dd December 3, 2010 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 SYNOPSIS 45.In ieeefp.h 46.Bd -literal 47typedef enum { 48 FP_RN, /* round to nearest */ 49 FP_RM, /* round down to minus infinity */ 50 FP_RP, /* round up to plus infinity */ 51 FP_RZ /* truncate */ 52} fp_rnd_t; 53.Ed 54.Ft fp_rnd_t 55.Fn fpgetround void 56.Ft fp_rnd_t 57.Fn fpsetround "fp_rnd_t direction" 58.Bd -literal 59typedef enum { 60 FP_PS, /* 24 bit (single-precision) */ 61 FP_PRS, /* reserved */ 62 FP_PD, /* 53 bit (double-precision) */ 63 FP_PE /* 64 bit (extended-precision) */ 64} fp_prec_t; 65.Ed 66.Ft fp_prec_t 67.Fn fpgetprec void 68.Ft fp_prec_t 69.Fn fpsetprec "fp_prec_t precision" 70.Bd -literal 71#define fp_except_t int 72#define FP_X_INV 0x01 /* invalid operation */ 73#define FP_X_DNML 0x02 /* denormal */ 74#define FP_X_DZ 0x04 /* zero divide */ 75#define FP_X_OFL 0x08 /* overflow */ 76#define FP_X_UFL 0x10 /* underflow */ 77#define FP_X_IMP 0x20 /* (im)precision */ 78#define FP_X_STK 0x40 /* stack fault */ 79.Ed 80.Ft fp_except_t 81.Fn fpgetmask void 82.Ft fp_except_t 83.Fn fpsetmask "fp_except_t mask" 84.Ft fp_except_t 85.Fn fpgetsticky void 86.Ft fp_except_t 87.Fn fpresetsticky "fp_except_t sticky" 88.Sh DESCRIPTION 89The routines described herein are deprecated. 90New code should use the functionality provided by 91.Xr fenv 3 . 92.Pp 93When a floating point exception is detected, the exception sticky flag is 94set and the exception mask is tested. 95If the mask is set, then a trap 96occurs. 97These routines allow both setting the floating point exception 98masks, and resetting the exception sticky flags after an exception is 99detected. 100In addition, they allow setting the floating point rounding mode 101and precision. 102.Pp 103The 104.Fn fpgetround 105function 106returns the current floating point rounding mode. 107.Pp 108The 109.Fn fpsetround 110function 111sets the floating point rounding mode and returns 112the previous mode. 113.Pp 114The 115.Fn fpgetprec 116function 117returns the current floating point precision. 118.Pp 119The 120.Fn fpsetprec 121function 122sets the floating point precision and returns 123the previous precision. 124.Pp 125The 126.Fn fpgetmask 127function 128returns the current floating point exception masks. 129.Pp 130The 131.Fn fpsetmask 132function 133sets the floating point exception masks and returns the 134previous masks. 135.Pp 136The 137.Fn fpgetsticky 138function 139returns the current floating point sticky flags. 140.Pp 141The 142.Fn fpresetsticky 143function 144clears the floating point sticky flags and returns 145the previous flags. 146.Pp 147Sample code which prevents a trap on divide-by-zero: 148.Bd -literal -offset indent 149fpsetmask(~FP_X_DZ); 150a = 1.0; 151b = 0; 152c = a / b; 153fpresetsticky(FP_X_DZ); 154fpsetmask(FP_X_DZ); 155.Ed 156.Sh IMPLEMENTATION NOTES 157The 158.Fn fpgetprec 159and 160.Fn fpsetprec 161functions provide functionality unavailable on many platforms. 162At present, they are implemented only on the i386 and amd64 platforms. 163Changing precision is not a supported feature: 164it may be ineffective when code is compiled to take advantage of SSE, 165and many library functions and compiler optimizations depend upon the 166default precision for correct behavior. 167.Sh SEE ALSO 168.Xr fenv 3 , 169.Xr isnan 3 170.Sh HISTORY 171These routines are based on SysV/386 routines of the same name. 172.Sh CAVEATS 173After a floating point exception and before a mask is set, the sticky 174flags must be reset. 175If another exception occurs before the sticky 176flags are reset, then a wrong exception type may be signaled. 177