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@(#)fpgetround.3 1.0 (Berkeley) 9/23/93
$FreeBSD$
.Dd December 3, 2010 .Dt FPGETROUND 3 .Os .Sh NAME .Nm fpgetround , .Nm fpsetround , .Nm fpsetprec , .Nm fpgetprec , .Nm fpgetmask , .Nm fpsetmask , .Nm fpgetsticky , .Nm fpresetsticky .Nd IEEE floating point interface .Sh SYNOPSIS n ieeefp.h d -literal typedef enum { FP_RN, /* round to nearest */ FP_RM, /* round down to minus infinity */ FP_RP, /* round up to plus infinity */ FP_RZ /* truncate */ } fp_rnd_t; .Ed .Ft fp_rnd_t .Fn fpgetround void .Ft fp_rnd_t .Fn fpsetround "fp_rnd_t direction" d -literal typedef enum { FP_PS, /* 24 bit (single-precision) */ FP_PRS, /* reserved */ FP_PD, /* 53 bit (double-precision) */ FP_PE /* 64 bit (extended-precision) */ } fp_prec_t; .Ed .Ft fp_prec_t .Fn fpgetprec void .Ft fp_prec_t .Fn fpsetprec "fp_prec_t precision" d -literal #define fp_except_t int #define FP_X_INV 0x01 /* invalid operation */ #define FP_X_DNML 0x02 /* denormal */ #define FP_X_DZ 0x04 /* zero divide */ #define FP_X_OFL 0x08 /* overflow */ #define FP_X_UFL 0x10 /* underflow */ #define FP_X_IMP 0x20 /* (im)precision */ #define FP_X_STK 0x40 /* stack fault */ .Ed .Ft fp_except_t .Fn fpgetmask void .Ft fp_except_t .Fn fpsetmask "fp_except_t mask" .Ft fp_except_t .Fn fpgetsticky void .Ft fp_except_t .Fn fpresetsticky "fp_except_t sticky" .Sh DESCRIPTION The routines described herein are deprecated. New code should use the functionality provided by .Xr fenv 3 .
p When a floating point exception is detected, the exception sticky flag is set and the exception mask is tested. If the mask is set, then a trap occurs. These routines allow both setting the floating point exception masks, and resetting the exception sticky flags after an exception is detected. In addition, they allow setting the floating point rounding mode and precision.
p The .Fn fpgetround function returns the current floating point rounding mode.
p The .Fn fpsetround function sets the floating point rounding mode and returns the previous mode.
p The .Fn fpgetprec function returns the current floating point precision.
p The .Fn fpsetprec function sets the floating point precision and returns the previous precision.
p The .Fn fpgetmask function returns the current floating point exception masks.
p The .Fn fpsetmask function sets the floating point exception masks and returns the previous masks.
p The .Fn fpgetsticky function returns the current floating point sticky flags.
p The .Fn fpresetsticky function clears the floating point sticky flags and returns the previous flags.
p Sample code which prevents a trap on divide-by-zero: d -literal -offset indent fpsetmask(~FP_X_DZ); a = 1.0; b = 0; c = a / b; fpresetsticky(FP_X_DZ); fpsetmask(FP_X_DZ); .Ed .Sh IMPLEMENTATION NOTES The .Fn fpgetprec and .Fn fpsetprec functions provide functionality unavailable on many platforms. At present, they are implemented only on the i386 and amd64 platforms. Changing precision isn't a supported feature: it may be ineffective when code is compiled to take advantage of SSE, and many library functions and compiler optimizations depend upon the default precision for correct behavior. .Sh SEE ALSO .Xr fenv 3 , .Xr isnan 3 .Sh HISTORY These routines are based on SysV/386 routines of the same name. .Sh CAVEATS After a floating point exception and before a mask is set, the sticky flags must be reset. If another exception occurs before the sticky flags are reset, then a wrong exception type may be signaled.