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download PDF document: fpgetround.3.pdf

FPGETROUND(3) FreeBSD Library Functions Manual FPGETROUND(3)
NAME fpgetround, fpsetround, fpsetprec, fpgetprec, fpgetmask, fpsetmask, fpgetsticky, fpresetsticky - IEEE floating point interface
SYNOPSIS #include <ieeefp.h>
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; fp_rnd_t fpgetround(void);
fp_rnd_t fpsetround(fp_rnd_t direction);
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; fp_prec_t fpgetprec(void);
fp_prec_t fpsetprec(fp_prec_t precision);
#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 */ fp_except_t fpgetmask(void);
fp_except_t fpsetmask(fp_except_t mask);
fp_except_t fpgetsticky(void);
fp_except_t fpresetsticky(fp_except_t sticky);
DESCRIPTION The routines described herein are deprecated. New code should use the functionality provided by fenv(3).
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
The fpsetround() function sets the floating point rounding mode and returns the previous mode.
The fpgetprec() function returns the current floating point precision.
The fpsetprec() function sets the floating point precision and returns the previous precision.
The fpgetmask() function returns the current floating point exception masks.
The fpsetmask() function sets the floating point exception masks and returns the previous masks.
The fpgetsticky() function returns the current floating point sticky flags.
The fpresetsticky() function clears the floating point sticky flags and returns the previous flags.
Sample code which prevents a trap on divide-by-zero:
fpsetmask(~FP_X_DZ); a = 1.0; b = 0; c = a / b; fpresetsticky(FP_X_DZ); fpsetmask(FP_X_DZ);
IMPLEMENTATION NOTES The fpgetprec() and fpsetprec() functions provide functionality unavailable on many platforms. At present, they are implemented only on the i386 and amd64 platforms. Changing precision is not 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.
SEE ALSO fenv(3), isnan(3)
HISTORY These routines are based on SysV/386 routines of the same name.
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.
FreeBSD 14.0-RELEASE-p11 December 3, 2010 FreeBSD 14.0-RELEASE-p11