##### 6.3.2.1 Scripts Used by `configure`

`configure` uses some other scripts to help in its work:

- The standard GNU `config.sub` and `config.guess` files, kept in the top level directory, are used. FIXME: when is the `config.guess` file in the `gcc` directory (that just calls the top level one) used?
- The file `config.gcc` is used to handle configuration specific to the particular target machine. The file `config.build` is used to handle configuration specific to the particular build machine. The file `config.host` is used to handle configuration specific to the particular host machine. (In general, these should only be used for features that cannot reasonably be tested in Autoconf feature tests.) See The `config.build`; `config.host`; and `config.gcc` Files, for details of the contents of these files.
- Each language subdirectory has a file `language/config-lang.in` that is used for front-end-specific configuration. See The Front End `config-lang.in` File, for details of this file.
- A helper script `configure.frag` is used as part of creating the output of `configure`.