+@item
+This function is missing on some platforms:
+FreeBSD 5.2.1, NetBSD 5.0, OpenBSD 3.8, Minix 3.1.8, AIX 5.1, older IRIX 6.5, OSF/1 4.0, Solaris 9, MSVC 9, Interix 3.5.
+@item
+This function is not declared on some platforms:
+IRIX 6.5.
+@item
+This function returns grossly wrong results on some platforms:
+OpenBSD 4.9.