25.3.2.1 8.3 Filenames

As discussed earlier, DOS file systems have severe restrictions on possible file names: they must follow an 8.3 format. See section 15.3.5.3 DOS Filename Restrictions.

This is quite a severe limitation, and affects some of the inner workings of GNU Autotools in two ways. The first is handled automatically, in that if .libs isn't a legal directory name on the host system, Libtool and Automake will use the directory _libs instead. The other is that the traditional `config.h.in' file is not legal under this scheme, and it must be worked around with a little known feature of Autoconf:

AC_CONFIG_HEADER(config.h:config.hin)