-AC_DEFINE_UNQUOTED(PATH_SEPARATOR, ':')
-AC_DEFINE_UNQUOTED(PATH_SEPARATOR_STR, ":")
+AC_DEFINE_UNQUOTED([PATH_SEPARATOR], [':'],
+ [Character used to separate path components.])
+AC_DEFINE_UNQUOTED([PATH_SEPARATOR_STR], [":"],
+ [Character used to separate path components, as string.])