+@item
+This function is missing on some platforms:
+NetBSD 5.0, OpenBSD 3.8, Minix 3.1.8, HP-UX 11, IRIX 6.5, Solaris 9, Cygwin, Interix 3.5, BeOS.
+@item
+This function is only defined as a macro with arguments on some platforms:
+MSVC 9.
+@item
+This function returns a minus zero for a minus zero argument on some platforms:
+IRIX 6.5 with gcc 4.2.4.