SYNOPSIS: Added feature test macro requirements.

RETURN VALUE: Added details for special argument cases.
Rewrote ERRORS section; noted that errno is not always set; see
also http://sources.redhat.com/bugzilla/show_bug.cgi?id=6783.
Updated CONFORMING TO.
SYNOPSIS: Added feature test macro requirements.
RETURN VALUE: Added details for special argument cases.
Rewrote ERRORS section; noted that errno is not always set; see
also http://sources.redhat.com/bugzilla/show_bug.cgi?id=6783.
Updated CONFORMING TO.

man3/fmod.3

@@ -1,4 +1,6 @@
 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
+.\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
+.\"     <mtk.manpages@gmail.com>
 .\"
 .\" Permission is granted to make and distribute verbatim copies of this
 .\" manual provided the copyright notice and this permission notice are
@@ -28,7 +30,7 @@
 .\" Modified 2002-07-27 by Walter Harms
 .\" 	(walter.harms@informatik.uni-oldenburg.de)
 .\"
-.TH FMOD 3  2002-07-27 "" "Linux Programmer's Manual"
+.TH FMOD 3  2008-07-29 "" "Linux Programmer's Manual"
 .SH NAME
 fmod, fmodf, fmodl \- floating-point remainder function
 .SH SYNOPSIS
@@ -43,28 +45,94 @@ fmod, fmodf, fmodl \- floating-point remainder function
 .fi
 .sp
 Link with \fI\-lm\fP.
+.sp
+.in -4n
+Feature Test Macro Requirements for glibc (see
+.BR feature_test_macros (7)):
+.in
+.sp
+.ad l
+.BR fmodf (),
+.BR fmodl ():
+_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE; or
+.I cc\ -std=c99
+.ad b
 .SH DESCRIPTION
 The
 .BR fmod ()
-function computes the remainder of dividing \fIx\fP by
+function computes the floating-point remainder of dividing \fIx\fP by
 \fIy\fP.
 The return value is \fIx\fP \- \fIn\fP * \fIy\fP, where \fIn\fP
 is the quotient of \fIx\fP / \fIy\fP, rounded towards zero to an integer.
 .SH "RETURN VALUE"
-The
+On success, these
-.BR fmod ()
+functions return the value \fIx\fP\ \-\ \fIn\fP*\fIy\fP,
-function returns the remainder, unless \fIy\fP is zero,
+for some integer \fIn\fP,
-when the function fails and \fIerrno\fP is set.
+such that the returned value has the same sign as
+.I x
+and a magnitude less than the magnitude of
+.IR y .
+
+If
+.I x
+or
+.I y
+is a NaN, a NaN is returned.
+
+If
+.I x
+is an infinity, 
+a "domain error" occurs, and
+a NaN is returned.
+
+If
+.I y
+is zero,
+a "domain error" occurs, and
+a NaN is returned.
+
+If
+.I x
+is +0 (\-0), and
+.I y
+is not zero, +0 (\-0) is returned.
 .SH ERRORS
+See
+.BR math_error (7)
+for information on how to determine whether an error has occurred
+when calling these functions.
+.PP
+The following errors can occur:
 .TP
-.B EDOM
+Domain error: \fIx\fP is an infinity
-The denominator \fIy\fP is zero.
+.\" .I errno
+.\" is set to
+.\" .BR EDOM .
+An invalid floating-point exception
+.RB ( FE_INVALID )
+is raised.
+.IP
+These functions do not set
+.IR errno
+for this case.
+.\" FIXME . Is it intentional that these functions do not set errno?
+.\" They do set errno for the y == 0 case, below.
+.\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6784
+.TP
+Domain error: \fIy\fP is zero
+.I errno
+is set to
+.BR EDOM .
+An invalid floating-point exception
+.RB ( FE_INVALID )
+is raised.
+.\" POSIX.1 documents an optional underflow error, but AFAICT it doesn't
+.\" (can't?) occur -- mtk, Jul 2008
 .SH "CONFORMING TO"
+C99, POSIX.1-2001.
+The variant returning
+.I double
+also conforms to
 SVr4, 4.3BSD, C89.
-The
-.I float
-and
-.I "long double"
-variants are C99 requirements.
 .SH "SEE ALSO"
 .BR remainder (3)