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.