X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;f=doc%2Fposix-functions%2Fisnan.texi;h=c835853f067f79a03db9765d241ab80f176e5450;hb=fc80165c92e8b92da6e88e4fdb9c472125124fa0;hp=90395c7d30df5c53a600e51f53938c4cc68139b5;hpb=2b6c08c775ae4e80b52aa41058ea5939f778b44b;p=gnulib.git

diff --git a/doc/posix-functions/isnan.texi b/doc/posix-functions/isnan.texi
index 90395c7d3..c835853f0 100644
--- a/doc/posix-functions/isnan.texi
+++ b/doc/posix-functions/isnan.texi
@@ -2,12 +2,26 @@
 @section @code{isnan}
 @findex isnan
 
-POSIX specification: @url{http://www.opengroup.org/susv3xsh/isnan.html}
+POSIX specification: @url{http://www.opengroup.org/onlinepubs/9699919799/functions/isnan.html}
 
-Gnulib module: ---
+Gnulib module: isnan
 
 Portability problems fixed by Gnulib:
 @itemize
+@item
+@code{isnan} was introduced with C99 and is thus commonly not present
+on pre-C99 systems.
+@item
+On IRIX 6.5 with @code{cc}, @code{isnan} does not recognize some NaNs.
+@item
+On NetBSD/i386 and glibc/ia64, @code{isnan} does not recognize some
+forms of NaNs, such as pseudo-NaNs, pseudo-Infinities, and
+unnormalized numbers.
+@item
+On i686 and @var{x}86-64, @code{__builtin_isnanl} (and thus
+@code{isnan} implementations based on it) in GCC 4.0 and later does
+not recognize pseudo-denormals as NaNs, and similarly for
+pseudo-zeroes, unnormalized numbers, and pseudo-denormals on ia64.
 @end itemize
 
 Portability problems not fixed by Gnulib: