+This function is missing on some platforms:
+Minix 3.1.8, AIX 4.3.2, IRIX 6.5, OSF/1 5.1, Solaris 9, mingw, MSVC 9.
+@item
+This function is declared but not defined on some platforms:
+IRIX 6.5.30.
+@item
+This function is not declared (without @code{-D_GNU_SOURCE}) on some platforms:
+glibc 2.8.
+@item