SYNOPSIS: Added feature test macro requirements.

RETURN VALUE: Added details for special argument cases.
Added (null) ERRORS section.
CONFORMING TO: Added POSIX.1-2001.

man3/modf.3

@@ -28,7 +28,7 @@
 .\" Modified 2002-07-27 by Walter Harms
 .\" 	(walter.harms@informatik.uni-oldenburg.de)
 .\"
-.TH MODF 3  2002-07-27 ""  "Linux Programmer's Manual"
+.TH MODF 3  2008-07-29 ""  "Linux Programmer's Manual"
 .SH NAME
 modf, modff, modfl \- extract signed integral and fractional values from
 floating-point number
@@ -44,23 +44,48 @@ floating-point number
 .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 modf (),
+.BR modl ():
+_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE; or
+.I cc\ -std=c99
+.ad b
 .SH DESCRIPTION
 The
 .BR modf ()
 function breaks the argument \fIx\fP into an integral
 part and a fractional part, each of which has the same sign as \fIx\fP.
-The integral part is stored in \fIiptr\fP.
+The integral part is stored in the location pointed to by \fIiptr\fP.
 .SH "RETURN VALUE"
 The
 .BR modf ()
 function returns the fractional part of \fIx\fP.
+
+If
+.I x
+is a NaN, a NaN is returned, and
+.IR *iptr 
+is set to a NaN.
+
+If
+.I x
+is positive infinity (negative infinity), +0 (-0) is returned, and
+.IR *iptr
+is set to positive infinity (negative infinity).
+.SH ERRORS
+No errors occur.
 .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 frexp (3),
 .BR ldexp (3)