+@item
+This function is missing on some platforms:
+Minix 3.1.8, AIX 5.1, HP-UX 11, IRIX 6.5, Solaris 9, MSVC 9.
+@item
+This function returns a wrong result for a zero argument on some platforms:
+OpenBSD 4.9.
+@item
+This function returns a wrong result for an infinite argument on some platforms:
+NetBSD 5.1, OpenBSD 4.9.