NAME
fpgetround, fpsetround, fpsetprec, fpgetprec, fpgetmask, fpsetmask, fpgetsticky, fpresetsticky — IEEE floating point interface
SYNOPSIS
#include <ieeefp.h>
typedef enum {
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FP_RN, |
/* round to nearest */ |
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FP_RM, |
/* round down to minus infinity */ |
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FP_RP, |
/* round up to plus infinity */ |
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FP_RZ |
/* truncate */ |
} fp_rnd_t;
fp_rnd_t
fpgetround(void);
fp_rnd_t
fpsetround(fp_rnd_t direction);
typedef enum {
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FP_PS, |
/* 24 bit (single-precision) */ |
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FP_PRS, |
/* reserved */ |
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FP_PD, |
/* 53 bit (double-precision) */ |
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FP_PE |
/* 64 bit (extended-precision) */ |
} fp_prec_t;
fp_prec_t
fpgetprec(void);
fp_prec_t
fpsetprec(fp_prec_t precision);
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#define fp_except_t |
int |
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#define FP_X_INV |
0x01 |
/* invalid operation */ |
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#define FP_X_DNML |
0x02 |
/* denormal */ |
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#define FP_X_DZ |
0x04 |
/* zero divide */ |
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#define FP_X_OFL |
0x08 |
/* overflow */ |
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#define FP_X_UFL |
0x10 |
/* underflow */ |
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#define FP_X_IMP |
0x20 |
/* (im)precision */ |
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#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 unavailable on many platforms. At present, they are implemented only on the i386 and amd64 platforms.
SEE ALSO
CAVEAT
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.
HISTORY
These routines are based on SysV/386 routines of the same name.
BSD August 23, 1993 BSD