+@item
+This function is missing on some platforms:
+glibc 2.3.6, MacOS X 10.3, FreeBSD 6.0, NetBSD 3.0, OpenBSD 3.8, AIX
+5.1, HP-UX 11, IRIX 6.5, OSF/1 5.1, Solaris 10, Cygwin 1.5.x, mingw, Interix 3.5, BeOS.
+But the replacement function is not safe to be used in libraries and is not multithread-safe.
+@item
+Some platforms declare this function in @code{stdio.h} instead of
+@code{unistd.h}:
+Cygwin 1.7.1.