fragments.texi: Mention config.host.

	* doc/fragments.texi: Mention config.host.
	* doc/sourcebuild.texi: Mention config.host.  Give brief descriptions
	of config.build, config.host, and config.gcc.

From-SVN: r70977

1 files changed, 23 insertions, 7 deletions

diff --git a/gcc/doc/sourcebuild.texi b/gcc/doc/sourcebuild.texi
index b5a11a9..73ad706 100644
--- a/gcc/doc/sourcebuild.texi
+++ b/gcc/doc/sourcebuild.texi
@@ -175,7 +175,8 @@ timestamp.
 
 @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
 
@@ -191,12 +192,14 @@ files, kept in the top level directory, are used.  FIXME: when is the
 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
@@ -208,7 +211,20 @@ creating the output of @file{configure}.
 @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.