fragments from the @file{config} directory. These are used to set
Makefile parameters that are not amenable to being calculated by
autoconf. The list of fragments to incorporate is set by
-@file{config.gcc} (and occasionally @file{config.build}); @xref{System Config}.
+@file{config.gcc} (and occasionally @file{config.build}
+and @file{config.host}); @xref{System Config}.
Fragments are named either @file{t-@var{target}} or @file{x-@var{host}},
depending on whether they are relevant to configuring GCC to produce
@menu
* Config Fragments:: Scripts used by @file{configure}.
-* System Config:: The @file{config.build} and @file{config.gcc} files.
+* System Config:: The @file{config.build}, @file{config.host}, and
+ @file{config.gcc} files.
* Configuration Files:: Files created by running @file{configure}.
@end menu
the top level one) used?
@item The file @file{config.gcc} is used to handle configuration
-specific to the particular host or target machine. The file
+specific to the particular target machine. The file
@file{config.build} is used to handle configuration specific to the
-particular build machine. (In general, these should only be used for
-features that cannot reasonably be tested in Autoconf feature tests.)
-@xref{System Config, , The @file{config.build} and @file{config.gcc} Files},
-for details of the contents of these files.
+particular build machine. The file @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.)
+@xref{System Config, , The @file{config.build}, @file{config.host},
+and @file{config.gcc} Files}, for details of the contents of these files.
@item Each language subdirectory has a file
@file{@var{language}/config-lang.in} that is used for
@end itemize
@node System Config
-@subsubsection The @file{config.build} and @file{config.gcc} Files
+@subsubsection The @file{config.build}, @file{config.host}, and @file{config.gcc} Files
+
+The @file{config.build} file contains specific rules for particular systems
+which GCC is built on. This should be used as rarely as possible, as the
+behavior of the build system can always be detected by autoconf.
+
+The @file{config.host} file contains specific rules for particular systems
+which GCC will run on. This is rarely needed.
+
+The @file{config.gcc} file contains specific rules for particular systems
+which GCC will generate code for. This is usually needed.
+
+Each file has a list of the shell variables it sets, with descriptions, at the
+top of the file.
FIXME: document the contents of these files, and what variables should
be set to control build, host and target configuration.