This function is missing on some platforms:
FreeBSD 5.2.1, NetBSD 3.0, OpenBSD 3.8, HP-UX 11, IRIX 6.5, Solaris 9, Cygwin, Interix 3.5.
@item
+This function is not declared on some platforms:
+MacOS X 10.3.
+@item
This function does not work on finite numbers on some platforms:
MacOS X 10.4/PowerPC, AIX 5.1, BeOS.
@item