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.Dd December 3, 2010 29.Dt FPGETROUND 3 30.Os 31.Sh NAME 32.Nm fpgetround , 33.Nm fpsetround , 34.Nm fpsetprec , 35.Nm fpgetprec , 36.Nm fpgetmask , 37.Nm fpsetmask , 38.Nm fpgetsticky , 39.Nm fpresetsticky 40.Nd IEEE floating point interface 41.Sh SYNOPSIS 42.In ieeefp.h 43.Bd -literal 44typedef enum { 45 FP_RN, /* round to nearest */ 46 FP_RM, /* round down to minus infinity */ 47 FP_RP, /* round up to plus infinity */ 48 FP_RZ /* truncate */ 49} fp_rnd_t; 50.Ed 51.Ft fp_rnd_t 52.Fn fpgetround void 53.Ft fp_rnd_t 54.Fn fpsetround "fp_rnd_t direction" 55.Bd -literal 56typedef enum { 57 FP_PS, /* 24 bit (single-precision) */ 58 FP_PRS, /* reserved */ 59 FP_PD, /* 53 bit (double-precision) */ 60 FP_PE /* 64 bit (extended-precision) */ 61} fp_prec_t; 62.Ed 63.Ft fp_prec_t 64.Fn fpgetprec void 65.Ft fp_prec_t 66.Fn fpsetprec "fp_prec_t precision" 67.Bd -literal 68#define fp_except_t int 69#define FP_X_INV 0x01 /* invalid operation */ 70#define FP_X_DNML 0x02 /* denormal */ 71#define FP_X_DZ 0x04 /* zero divide */ 72#define FP_X_OFL 0x08 /* overflow */ 73#define FP_X_UFL 0x10 /* underflow */ 74#define FP_X_IMP 0x20 /* (im)precision */ 75#define FP_X_STK 0x40 /* stack fault */ 76.Ed 77.Ft fp_except_t 78.Fn fpgetmask void 79.Ft fp_except_t 80.Fn fpsetmask "fp_except_t mask" 81.Ft fp_except_t 82.Fn fpgetsticky void 83.Ft fp_except_t 84.Fn fpresetsticky "fp_except_t sticky" 85.Sh DESCRIPTION 86The routines described herein are deprecated. 87New code should use the functionality provided by 88.Xr fenv 3 . 89.Pp 90When a floating point exception is detected, the exception sticky flag is 91set and the exception mask is tested. 92If the mask is set, then a trap 93occurs. 94These routines allow both setting the floating point exception 95masks, and resetting the exception sticky flags after an exception is 96detected. 97In addition, they allow setting the floating point rounding mode 98and precision. 99.Pp 100The 101.Fn fpgetround 102function 103returns the current floating point rounding mode. 104.Pp 105The 106.Fn fpsetround 107function 108sets the floating point rounding mode and returns 109the previous mode. 110.Pp 111The 112.Fn fpgetprec 113function 114returns the current floating point precision. 115.Pp 116The 117.Fn fpsetprec 118function 119sets the floating point precision and returns 120the previous precision. 121.Pp 122The 123.Fn fpgetmask 124function 125returns the current floating point exception masks. 126.Pp 127The 128.Fn fpsetmask 129function 130sets the floating point exception masks and returns the 131previous masks. 132.Pp 133The 134.Fn fpgetsticky 135function 136returns the current floating point sticky flags. 137.Pp 138The 139.Fn fpresetsticky 140function 141clears the floating point sticky flags and returns 142the previous flags. 143.Pp 144Sample code which prevents a trap on divide-by-zero: 145.Bd -literal -offset indent 146fpsetmask(~FP_X_DZ); 147a = 1.0; 148b = 0; 149c = a / b; 150fpresetsticky(FP_X_DZ); 151fpsetmask(FP_X_DZ); 152.Ed 153.Sh IMPLEMENTATION NOTES 154The 155.Fn fpgetprec 156and 157.Fn fpsetprec 158functions provide functionality unavailable on many platforms. 159At present, they are implemented only on the i386 and amd64 platforms. 160Changing precision is not a supported feature: 161it may be ineffective when code is compiled to take advantage of SSE, 162and many library functions and compiler optimizations depend upon the 163default precision for correct behavior. 164.Sh SEE ALSO 165.Xr fenv 3 , 166.Xr isnan 3 167.Sh HISTORY 168These routines are based on SysV/386 routines of the same name. 169.Sh CAVEATS 170After a floating point exception and before a mask is set, the sticky 171flags must be reset. 172If another exception occurs before the sticky 173flags are reset, then a wrong exception type may be signaled. 174