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fenv(5) fenv(5)

NAME

fenv - ﬂoating-point environment macros and functions

SYNOPSIS

#include <fenv.h>

DESCRIPTION

The header <fenv.h> declares two types and several macros and functions to provide access to the

ﬂoating-point environment. The ﬂoating-point environment refers collectively to the ﬂoating-point status

ﬂags and control modes. A ﬂoating-point status ﬂag is a system variable whose value is set (but never

cleared) when a ﬂoating-point exception is raised, which occurs as a side effect of exceptional ﬂoating-

point arithmetic to provide auxiliary information. A ﬂoating-point control mode is a system variable

whose value may be set by the user to affect the subsequent behavior of ﬂoating-point arithmetic; on HP

9000 and Itanium(R)-based systems the control modes include the rounding direction mode, the

gradual/ﬂush-to-zero underﬂow mode, and the trap enables.

The following types are deﬁned:

fenv_t Represents the entire ﬂoating-point environment.

fexcept_t Represents the ﬂoating-point exception ﬂags collectively.

The following macros represent the ﬂoating-point status ﬂags. They are deﬁned as integral constant

expressions with values such that bitwise ORs of all combinations of the macros result in distinct values.

FE_INEXACT The inexact exception.

FE_DIVBYZERO The division-by-zero exception.

FE_UNDERFLOW The underﬂow exception.

FE_OVERFLOW The overﬂow exception.

FE_INVALID The invalid operation exception.

FE_ALL_EXCEPT The bitwise OR of all exception macros.

The following macros represent the rounding direction modes. They are deﬁned as integral constant

expressions with distinct nonnegative values.

FE_TONEAREST The round-to-nearest rounding direction mode.

FE_UPWARD The round-toward-positive-inﬁnity rounding direction mode.

FE_DOWNWARD The round-toward-negative-inﬁnity rounding direction mode.

FE_TOWARDZERO The round-toward-zero rounding direction mode.

The following macro is deﬁned as a pointer to const-qualiﬁed

fenv_t:

FE_DFL_ENV The default ﬂoating-point environment.

To the ISO/IEC C99 speciﬁed facilities, the HP implementation adds four HP-speciﬁc functions:

feget-

flushtozero(), fesetflushtozero(), fegettrapenable()

, and fesettrapenable().

FILES

/usr/include/fenv.h