DragonFly On-Line Manual Pages

Search: Section:  

FPGETROUND(3)         DragonFly Library Functions Manual         FPGETROUND(3)


NAME

     fpgetround, fpsetround, fpsetprec, fpgetprec, fpgetmask, fpsetmask,
     fpgetsticky -- IEEE floating point interface


LIBRARY

     Standard C Library (libc, -lc)


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);


DESCRIPTION

     The routines described herein are deprecated.  New code should use the
     functionality provided by fe*() functions in the Math Library (libm,
     -lm).

     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.


IMPLEMENTATION NOTES

     The fpgetprec() and fpsetprec() functions provide functionality
     unavailable on many platforms.  At present, they are implemented only on
     the x86_64 platform.  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

     feclearexcept(3), feenableexcept(3), fegetenv(3), fegetround(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.

DragonFly 5.3                   August 9, 2018                   DragonFly 5.3

Search: Section: