+This file is required in all language subdirectories. @xref{Front End
+Makefile, , The Front End @file{Make-lang.in} File}, for details of its
+contents.
+@item lang.opt
+This file registers the set of switches that the front end accepts on
+the command line, and their @option{--help} text. @xref{Options}.
+@item lang-specs.h
+This file provides entries for @code{default_compilers} in
+@file{gcc.c} which override the default of giving an error that a
+compiler for that language is not installed.
+@item @var{language}-tree.def
+This file, which need not exist, defines any language-specific tree
+codes.
+@end table
+
+@node Front End Config
+@subsubsection The Front End @file{config-lang.in} File
+
+Each language subdirectory contains a @file{config-lang.in} file. In
+addition the main directory contains @file{c-config-lang.in}, which
+contains limited information for the C language. This file is a shell
+script that may define some variables describing the language:
+
+@table @code
+@item language
+This definition must be present, and gives the name of the language
+for some purposes such as arguments to @option{--enable-languages}.
+@item lang_requires
+If defined, this variable lists (space-separated) language front ends
+other than C that this front end requires to be enabled (with the
+names given being their @code{language} settings). For example, the
+Java front end depends on the C++ front end, so sets
+@samp{lang_requires=c++}.
+@item subdir_requires
+If defined, this variable lists (space-separated) front end directories
+other than C that this front end requires to be present. For example,
+the Objective-C++ front end uses source files from the C++ and
+Objective-C front ends, so sets @samp{subdir_requires="cp objc"}.
+@item target_libs
+If defined, this variable lists (space-separated) targets in the top
+level @file{Makefile} to build the runtime libraries for this
+language, such as @code{target-libobjc}.
+@item lang_dirs
+If defined, this variable lists (space-separated) top level
+directories (parallel to @file{gcc}), apart from the runtime libraries,
+that should not be configured if this front end is not built.
+@item build_by_default
+If defined to @samp{no}, this language front end is not built unless
+enabled in a @option{--enable-languages} argument. Otherwise, front
+ends are built by default, subject to any special logic in
+@file{configure.ac} (as is present to disable the Ada front end if the
+Ada compiler is not already installed).
+@item boot_language
+If defined to @samp{yes}, this front end is built in stage1 of the
+bootstrap. This is only relevant to front ends written in their own
+languages.
+@item compilers
+If defined, a space-separated list of compiler executables that will
+be run by the driver. The names here will each end
+with @samp{\$(exeext)}.
+@item outputs
+If defined, a space-separated list of files that should be generated
+by @file{configure} substituting values in them. This mechanism can
+be used to create a file @file{@var{language}/Makefile} from
+@file{@var{language}/Makefile.in}, but this is deprecated, building
+everything from the single @file{gcc/Makefile} is preferred.
+@item gtfiles
+If defined, a space-separated list of files that should be scanned by
+@file{gengtype.c} to generate the garbage collection tables and routines for
+this language. This excludes the files that are common to all front
+ends. @xref{Type Information}.
+
+@end table
+
+@node Front End Makefile
+@subsubsection The Front End @file{Make-lang.in} File
+
+Each language subdirectory contains a @file{Make-lang.in} file. It contains
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