Skip site navigation (1)Skip section navigation (2)

FreeBSD Man Pages

Man Page or Keyword Search:
Man Architecture
Apropos Keyword Search (all sections) Output format
home | help
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
     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.

     The fpgetround() function returns the current floating point rounding
     mode.

     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 unavail-
     able 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.

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	10.1		       December	3, 2010			  FreeBSD 10.1

NAME | SYNOPSIS | DESCRIPTION | IMPLEMENTATION NOTES | SEE ALSO | HISTORY | CAVEATS

Want to link to this manual page? Use this URL:
<https://www.freebsd.org/cgi/man.cgi?query=fpsetmask&sektion=3&manpath=FreeBSD+9.3-RELEASE>

home | help