.\" Copyright 2001 Andries Brouwer <aeb@cwi.nl>.
+.\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
+.\" <mtk.manpages@gmail.com>
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+.\"
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.\" responsibility for errors or omissions, or for damages resulting from
.\" have taken the same level of care in the production of this manual,
.\" which is licensed free of charge, as they might when working
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-.TH RINT 3 2001-05-31 "" "Linux Programmer's Manual"
+.TH RINT 3 2017-09-15 "" "Linux Programmer's Manual"
.SH NAME
-nearbyint, nearbyintf, nearbyintl, rint, rintf, rintl \- round to nearest integer
+nearbyint, nearbyintf, nearbyintl, rint, rintf, rintl \- round
+to nearest integer
.SH SYNOPSIS
.nf
.B #include <math.h>
-.sp
+.PP
.BI "double nearbyint(double " x );
-.br
.BI "float nearbyintf(float " x );
-.br
.BI "long double nearbyintl(long double " x );
-.sp
+.PP
.BI "double rint(double " x );
-.br
.BI "float rintf(float " x );
-.br
.BI "long double rintl(long double " x );
.fi
-.sp
-Link with \-lm.
+.PP
+Link with \fI\-lm\fP.
+.PP
+.in -4n
+Feature Test Macro Requirements for glibc (see
+.BR feature_test_macros (7)):
+.in
+.PP
+.ad l
+.BR nearbyint (),
+.BR nearbyintf (),
+.BR nearbyintl ():
+.RS 4
+_POSIX_C_SOURCE\ >=\ 200112L || _ISOC99_SOURCE
+.RE
+.br
+.BR rint ():
+.RS 4
+_ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
+ || _XOPEN_SOURCE\ >=\ 500
+.\" || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
+ || /* Since glibc 2.19: */ _DEFAULT_SOURCE
+ || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
+.RE
+.br
+.BR rintf (),
+.BR rintl ():
+.RS 4
+_ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
+ || /* Since glibc 2.19: */ _DEFAULT_SOURCE
+ || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
+.RE
+.ad b
.SH DESCRIPTION
The
-.BR nearbyint ()
-functions round their argument to an integer value in floating point
-format, using the current rounding direction and without raising the
+.BR nearbyint (),
+.BR nearbyintf (),
+and
+.BR nearbyintl ()
+functions round their argument to an integer value in floating-point
+format, using the current rounding direction (see
+.BR fesetround (3))
+and without raising the
.I inexact
exception.
-.LP
+When the current rounding direction is to nearest, these
+functions round halfway cases to the even integer in accordance with
+IEEE-754.
+.PP
The
-.BR rint ()
+.BR rint (),
+.BR rintf (),
+and
+.BR rintl ()
functions do the same, but will raise the
.I inexact
-exception when the result differs in value from the argument.
-.SH "RETURN VALUE"
-The rounded integer value. If \fIx\fP is integral or infinite,
-\fIx\fP itself is returned.
+exception
+.RB ( FE_INEXACT ,
+checkable via
+.BR fetestexcept (3))
+when the result differs in value from the argument.
+.SH RETURN VALUE
+These functions return the rounded integer value.
+.PP
+If
+.I x
+is integral, +0, \-0, NaN, or infinite,
+.I x
+itself is returned.
.SH ERRORS
-No errors other than EDOM and ERANGE can occur.
-If \fIx\fP is NaN, then NaN is returned and
-.I errno
-may be set to EDOM.
+No errors occur.
+POSIX.1-2001 documents a range error for overflows, but see NOTES.
+.SH ATTRIBUTES
+For an explanation of the terms used in this section, see
+.BR attributes (7).
+.TS
+allbox;
+lbw26 lb lb
+l l l.
+Interface Attribute Value
+T{
+.BR nearbyint (),
+.BR nearbyintf (),
+.br
+.BR nearbyintl (),
+.BR rint (),
+.br
+.BR rintf (),
+.BR rintl ()
+T} Thread safety MT-Safe
+.TE
+.SH CONFORMING TO
+C99, POSIX.1-2001, POSIX.1-2008.
.SH NOTES
-SUSv2 and POSIX 1003.1-2001 contain text about overflow (which might set
+SUSv2 and POSIX.1-2001 contain text about overflow (which might set
.I errno
-to ERANGE, or raise an exception).
+to
+.BR ERANGE ,
+or raise an
+.B FE_OVERFLOW
+exception).
In practice, the result cannot overflow on any current machine,
so this error-handling stuff is just nonsense.
(More precisely, overflow can happen only when the maximum value
of the exponent is smaller than the number of mantissa bits.
-For the IEEE-754 standard 32-bit and 64-bit floating point numbers
-the maximum value of the exponent is 128 (resp. 1024), and the number
-of mantissa bits is 24 (resp. 53).)
-.SH "CONFORMING TO"
-The
-.B rint()
-function conforms to 4.3BSD.
-The other functions are from C99.
-.SH "SEE ALSO"
+For the IEEE-754 standard 32-bit and 64-bit floating-point numbers
+the maximum value of the exponent is 128 (respectively, 1024),
+and the number of mantissa bits is 24 (respectively, 53).)
+.PP
+If you want to store the rounded value in an integer type,
+you probably want to use one of the functions described in
+.BR lrint (3)
+instead.
+.SH SEE ALSO
.BR ceil (3),
.BR floor (3),
.BR lrint (3),
-.BR nearbyint (3),
.BR round (3),
.BR trunc (3)
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