[pf3gnuchains/gcc-fork.git] / gcc / doc / sourcebuild.texi

@c Copyright (C) 2002 Free Software Foundation, Inc.
@c This is part of the GCC manual.
@c For copying conditions, see the file gcc.texi.

@node Source Tree
@chapter Source Tree Structure and Build System

This chapter describes the structure of the GCC source tree, and how
GCC is built.  The user documentation for building and installing GCC
is in a separate manual (@uref{http://gcc.gnu.org/install/}), with
which it is presumed that you are familiar.

@menu
* Configure Terms:: Configuration terminology and history.
* Top Level::       The top level source directory.
* gcc Directory::   The @file{gcc} subdirectory.
* Test Suites::     The GCC test suites.
@end menu

@include configterms.texi

@node Top Level
@section Top Level Source Directory

The top level source directory in a GCC distribution contains several
files and directories that are shared with other software
distributions such as that of GNU Binutils.  It also contains several
subdirectories that contain parts of GCC and its runtime libraries:

@table @file
@item boehm-gc
The Boehm conservative garbage collector, used as part of the Java
runtime library.

@item contrib
Contributed scripts that may be found useful in conjunction with GCC@.
One of these, @file{contrib/texi2pod.pl}, is used to generate man
pages from Texinfo manuals as part of the GCC build process.

@item fastjar
An implementation of the @command{jar} command, used with the Java
front end.

@item gcc
The main sources of GCC itself (except for runtime libraries),
including optimizers, support for different target architectures,
language front ends, and test suites.  @xref{gcc Directory, , The
@file{gcc} Subdirectory}, for details.

@item include
Headers for the @code{libiberty} library.

@item libf2c
The Fortran runtime library.

@item libffi
The @code{libffi} library, used as part of the Java runtime library.

@item libiberty
The @code{libiberty} library, used for portability and for some
generally useful data structures and algorithms.  @xref{Top, ,
Introduction, libiberty, @sc{gnu} libiberty}, for more information
about this library.

@item libjava
The Java runtime library.

@item libobjc
The Objective-C runtime library.

@item libstdc++-v3
The C++ runtime library.

@item maintainer-scripts
Scripts used by the @code{gccadmin} account on @code{gcc.gnu.org}.

@item zlib
The @code{zlib} compression library, used by the Java front end and as
part of the Java runtime library.
@end table

The build system in the top level directory, including how recursion
into subdirectories works and how building runtime libraries for
multilibs is handled, is documented in a separate manual, included
with GNU Binutils.  @xref{Top, , GNU configure and build system,
configure, The GNU configure and build system}, for details.

@node gcc Directory
@section The @file{gcc} Subdirectory

The @file{gcc} directory contains many files that are part of the C
sources of GCC, other files used as part of the configuration and
build process, and subdirectories including documentation and a
test suite.  The files that are sources of GCC are documented in a
separate chapter.  @xref{Passes, , Passes and Files of the Compiler}.

@menu
* Subdirectories:: Subdirectories of @file{gcc}.
* Configuration::  The configuration process, and the files it uses.
* Build::          The build system in the @file{gcc} directory.
* Makefile::       Targets in @file{gcc/Makefile}.
* Library Files::  Library source files and headers under @file{gcc/}.
* Headers::        Headers installed by GCC.
* Documentation::  Building documentation in GCC.
* Front End::      Anatomy of a language front end.
* Back End::       Anatomy of a target back end.
@end menu

@node Subdirectories
@subsection Subdirectories of @file{gcc}

The @file{gcc} directory contains the following subdirectories:

@table @file
@item @var{language}
Subdirectories for various languages.  Directories containing a file
@file{config-lang.in} are language subdirectories.  The contents of
the subdirectories @file{cp} (for C++) and @file{objc} (for
Objective-C) are documented in this manual (@pxref{Passes, , Passes
and Files of the Compiler}); those for other languages are not.
@xref{Front End, , Anatomy of a Language Front End}, for details of
the files in these directories.

@item config
Configuration files for supported architectures and operating
systems.  @xref{Back End, , Anatomy of a Target Back End}, for
details of the files in thie directory.

@item doc
Texinfo documentation for GCC, together with automatically generated
man pages and support for converting the installation manual to
HTML@.  @xref{Documentation}.

@item fixinc
The support for fixing system headers to work with GCC@.  See
@file{fixinc/README} for more information.  The headers fixed by this
mechanism are installed in @file{@var{libsubdir}/include}.  Along with
those headers, @file{README-fixinc} is also installed, as
@file{@var{libsubdir}/include/README}.

@item ginclude
System headers installed by GCC, mainly those required by the C
standard of freestanding implementations.  @xref{Headers, , Headers
Installed by GCC}, for details of when these and other headers are
installed.

@item intl
GNU @code{libintl}, from GNU @code{gettext}, for systems which do not
include it in libc.  Properly, this directory should be at top level,
parallel to the @file{gcc} directory.

@item po
Message catalogs with translations of messages produced by GCC into
various languages, @file{@var{language}.po}.  This directory also
contains @file{gcc.pot}, the template for these message catalogues,
@file{exgettext}, a wrapper around @command{gettext} to extract the
messages from the GCC sources and create @file{gcc.pot}, which is run
by @command{make gcc.pot}, and @file{EXCLUDES}, a list of files from
which messages should not be extracted.

@item testsuite
The GCC test suites (except for those for runtime libraries).
@xref{Test Suites}.
@end table

@node Configuration
@subsection Configuration in the @file{gcc} Directory

The @file{gcc} directory is configured with an Autoconf-generated
script @file{configure}.  The @file{configure} script is generated
from @file{configure.in} and @file{aclocal.m4}.  From the files
@file{configure.in} and @file{acconfig.h}, Autoheader generates the
file @file{config.in}.  The file @file{cstamp-h.in} is used as a
timestamp.

@menu
* Config Fragments::     Scripts used by @file{configure}.
* System Config::        The @file{config.gcc} file.
* Configuration Files::  Files created by running @file{configure}.
@end menu

@node Config Fragments
@subsubsection Scripts Used by @file{configure}

@file{configure} uses some other scripts to help in its work:

@itemize @bullet
@item The standard GNU @file{config.sub} and @file{config.guess}
files, kept in the top level directory, are used.  FIXME: when is the
@file{config.guess} file in the @file{gcc} directory (that just calls
the top level one) used?

@item The file @file{config.gcc} is used to handle configuration
specific to the particular build, host or target machine.  (In
general, this should only be used for features that cannot reasonably
be tested in Autoconf feature tests.)  @xref{System Config, , The
@file{config.gcc} File}, for details of the contents of this file.

@item Each language subdirectory has a file
@file{@var{language}/config-lang.in} that is used for
front-end-specific configuration.  @xref{Front End Config, , The Front
End @file{config-lang.in} File}, for details of this file.

@item A helper script @file{configure.frag} is used as part of
creating the output of @file{configure}.
@end itemize

@node System Config
@subsubsection The @file{config.gcc} File

FIXME: document the contents of this file, and what variables should
be set to control build, host and target configuration.

@include configfiles.texi

@node Build
@subsection Build System in the @file{gcc} Directory

FIXME: describe the build system, including what is built in what
stages.  Also list the various source files that are used in the build
process but aren't source files of GCC itself and so aren't documented
below (@pxref{Passes}).

@include makefile.texi

@node Library Files
@subsection Library Source Files and Headers under the @file{gcc} Directory

FIXME: list here, with explanation, all the C source files and headers
under the @file{gcc} directory that aren't built into the GCC
executable but rather are part of runtime libraries and object files,
such as @file{crtstuff.c} and @file{unwind-dw2.c}.  @xref{Headers, ,
Headers Installed by GCC}, for more information about the
@file{ginclude} directory.

@node Headers
@subsection Headers Installed by GCC

In general, GCC expects the system C library to provide most of the
headers to be used with it.  However, GCC will fix those headers if
necessary to make them work with GCC, and will install some headers
required of freestanding implementations.  These headers are installed
in @file{@var{libsubdir}/include}.  Headers for non-C runtime
libraries are also installed by GCC; these are not documented here.
(FIXME: document them somewhere.)

Several of the headers GCC installs are in the @file{ginclude}
directory.  These headers, @file{iso646.h},
@file{stdarg.h}, @file{stdbool.h}, @file{stddef.h} and
@file{varargs.h}, are installed in @file{@var{libsubdir}/include},
unless the target Makefile fragment (@pxref{Target Fragment})
overrides this by setting @code{USER_H}.

In addition to these headers and those generated by fixing system
headers to work with GCC, some other headers may also be installed in
@file{@var{libsubdir}/include}.  @file{config.gcc} may set
@code{extra_headers}; this specifies additional headers under
@file{config} to be installed on some systems.  GCC normally installs
a @code{<float.h>} file; these are kept as
@file{config/float-@var{format}.h}, where @var{format} is specified by
a @code{float_format} setting in @file{config.gcc}, and a setting
@samp{float_format=none} disables installation of this header.  GCC
also installs its own version of @code{<limits.h>}; this is generated
from @file{glimits.h}, together with @file{limitx.h} and
@file{limity.h} if the system also has its own version of
@code{<limits.h>}.  (GCC provides its own header because it is
required of ISO C freestanding implementations, but needs to include
the system header from its own header as well because other standards
such as POSIX specify additional values to be defined in
@code{<limits.h>}.)  The system's @code{<limits.h>} header is used via
@file{@var{libsubdir}/include/syslimits.h}, which is copied from
@file{gsyslimits.h} if it does not need fixing to work with GCC; if it
needs fixing, @file{syslimits.h} is the fixed copy.

@node Documentation
@subsection Building Documentation

The main GCC documentation is in the form of manuals in Texinfo
format.  These are installed in Info format, and DVI versions may be
generated by @command{make dvi}.  In addition, some man pages are
generated from the Texinfo manuals, there are some other text files
with miscellaneous documentation, and runtime libraries have their own
documentation outside the @file{gcc} directory.  FIXME: document the
documentation for runtime libraries somewhere.

@menu
* Texinfo Manuals::      GCC manuals in Texinfo format.
* Man Page Generation::  Generating man pages from Texinfo manuals.
* Miscellaneous Docs::   Miscellaneous text files with documentation.
@end menu

@node Texinfo Manuals
@subsubsection Texinfo Manuals

The manuals for GCC as a whole, and the C and C++ front ends, are in
files @file{doc/*.texi}.  Other front ends have their own manuals in
files @file{@var{language}/*.texi}.  Common files
@file{doc/include/*.texi} are provided which may be included in
multiple manuals; the following files are in @file{doc/include}:

@table @file
@item fdl.texi
The GNU Free Documentation License.
@item funding.texi
The section ``Funding Free Software''.
@item gcc-common.texi
Common definitions for manuals.
@item gpl.texi
The GNU General Public License.
@item texinfo.tex
A copy of @file{texinfo.tex} known to work with the GCC manuals.
@end table

DVI formatted manuals are generated by @command{make dvi}, which uses
@command{texi2dvi} (via the Makefile macro @code{$(TEXI2DVI)}).  Info
manuals are generated by @command{make info} (which is run as part of
a bootstrap); this generates the manuals in the source directory,
using @command{makeinfo} via the Makefile macro @code{$(MAKEINFO)},
and they are included in release distributions.

Manuals are also provided on the GCC web site, in both HTML and
PostScript forms.  This is done via the script
@file{maintainer-scripts/update_web_docs}.  Each manual to be
provided online must be listed in the definition of @code{MANUALS} in
that file; a file @file{@var{name}.texi} must only appear once in the
source tree, and the output manual must have the same name as the
source file.  (However, other Texinfo files, included in manuals but
not themselves the root files of manuals, may have names that appear
more than once in the source tree.)  The manual file
@file{@var{name}.texi} should only include other files in its own
directory or in @file{doc/include}.  HTML manuals will be generated by
@command{makeinfo --html} and PostScript manuals by @command{texi2dvi}
and @command{dvips}.  All Texinfo files that are parts of manuals must
be checked into CVS, even if they are generated files, for the
generation of online manuals to work.

The installation manual, @file{doc/install.texi}, is also provided on
the GCC web site.  The HTML version is generated by the script
@file{doc/install.texi2html}.

@node Man Page Generation
@subsubsection Man Page Generation

Because of user demand, in addition to full Texinfo manuals, man pages
are provided which contain extracts from those manuals.  These man
pages are generated from the Texinfo manuals using
@file{contrib/texi2pod.pl} and @command{pod2man}.  (The man page for
@command{g++}, @file{cp/g++.1}, just contains a @samp{.so} reference
to @file{gcc.1}, but all the other man pages are generated from
Texinfo manuals.)

Because many systems may not have the necessary tools installed to
generate the man pages, they are only generated if the
@file{configure} script detects that recent enough tools are
installed, and the Makefiles allow generating man pages to fail
without aborting the build.  Man pages are also included in release
distributions.  They are generated in the source directory.

Magic comments in Texinfo files starting @samp{@@c man} control what
parts of a Texinfo file go into a man page.  Only a subset of Texinfo
is supported by @file{texi2pod.pl}, and it may be necessary to add
support for more Texinfo features to this script when generating new
man pages.  To improve the man page output, some special Texinfo
macros are provided in @file{doc/include/gcc-common.texi} which
@file{texi2pod.pl} understands:

@table @code
@item @@gcctabopt
Use in the form @samp{@@table @@gcctabopt} for tables of options,
where for printed output the effect of @samp{@@code} is better than
that of @samp{@@option} but for man page output a different effect is
wanted.
@item @@gccoptlist
Use for summary lists of options in manuals.
@item @@gol
Use at the end of each line inside @samp{@@gccoptlist}.  This is
necessary to avoid problems with differences in how the
@samp{@@gccoptlist} macro is handled by different Texinfo formatters.
@end table

FIXME: describe the @file{texi2pod.pl} input language and magic
comments in more detail.

@node Miscellaneous Docs
@subsubsection Miscellaneous Documentation

In addition to the formal documentation that is installed by GCC,
there are several other text files with miscellaneous documentation:

@table @file
@item ABOUT-GCC-NLS
Notes on GCC's Native Language Support.  FIXME: this should be part of
this manual rather than a separate file.
@item ABOUT-NLS
Notes on the Free Translation Project.
@item COPYING
The GNU General Public License.
@item COPYING.LIB
The GNU Lesser General Public License.
@item *ChangeLog*
@itemx */ChangeLog*
Change log files for various parts of GCC@.
@item LANGUAGES
Details of a few changes to the GCC front-end interface.  FIXME: the
information in this file should be part of general documentation of
the front-end interface in this manual.
@item ONEWS
Information about new features in old versions of GCC@.  (For recent
versions, the information is on the GCC web site.)
@item README.Portability
Information about portability issues when writing code in GCC@.  FIXME:
why isn't this part of this manual or of the GCC Coding Conventions?
@item SERVICE
A pointer to the GNU Service Directory.
@end table

FIXME: document such files in subdirectories, at least @file{config},
@file{cp}, @file{objc}, @file{testsuite}.

@node Front End
@subsection Anatomy of a Language Front End

A front end for a language in GCC has the following parts:

@itemize @bullet
@item
A directory @file{@var{language}} under @file{gcc} containing source
files for that front end.  @xref{Front End Directory, , The Front End
@file{@var{language}} Directory}, for details.
@item
A mention of the language in the list of supported languages in
@file{gcc/doc/install.texi}.
@item
Details of contributors to that front end in
@file{gcc/doc/contrib.texi}.  If the details are in that front end's
own manual then there should be a link to that manual's list in
@file{contrib.texi}.
@item
Information about support for that language in
@file{gcc/doc/frontends.texi}.
@item
Information about standards for that language, and the front end's
support for them, in @file{gcc/doc/standards.texi}.  This may be a
link to such information in the front end's own manual.
@item
Details of source file suffixes for that language and @option{-x
@var{lang}} options supported, in @file{gcc/doc/invoke.texi}.
@item
Entries in @code{default_compilers} in @file{gcc.c} for source file
suffixes for that language.
@item
Preferably test suites, which may be under @file{gcc/testsuite} or
runtime library directories.  FIXME: document somewhere how to write
test suite harnesses.
@item
Probably a runtime library for the language, outside the @file{gcc}
directory.  FIXME: document this further.
@item
Details of the directories of any runtime libraries in
@file{gcc/doc/sourcebuild.texi}.
@end itemize

If the front end is added to the official GCC CVS repository, the
following are also necessary:

@itemize @bullet
@item
At least one GNATS category for bugs in that front end and runtime
libraries.  This category needs to be mentioned in
@file{gcc/gccbug.in}, and in @file{gnats.html} on the GCC web site, as
well as being added to the GNATS database.
@item
Normally, one or more maintainers of that front end listed in
@file{MAINTAINERS}.
@item
Mentions on the GCC web site in @file{index.html} and
@file{frontends.html}, with any relevant links on
@file{readings.html}.  (Front ends that are not an official part of
GCC may also be listed on @file{frontends.html}, with relevant links.)
@item
A news item on @file{index.html}, and possibly an announcement on the
@email{gcc-announce@@gcc.gnu.org} mailing list.
@item
The front end's manuals should be mentioned in
@file{maintainer-scripts/update_web_docs} (@pxref{Texinfo Manuals})
and the online manuals should be linked to from
@file{onlinedocs/index.html}.
@item
Any old releases or CVS repositories of the front end, before its
inclusion in GCC, should be made available on the GCC FTP site
@uref{ftp://gcc.gnu.org/pub/gcc/old-releases/}.
@item
The release and snapshot script @file{maintainer-scripts/gcc_release}
should be updated to generate appropriate tarballs for this front end.
The associated @file{maintainer-scripts/snapshot-README} and
@file{maintainer-scripts/snapshot-index.html} files should be updated
to list the tarballs and diffs for this front end.
@item
If this front end includes its own version files that include the
current date, @file{maintainer-scripts/update_version} should be
updated accordingly.
@item
@file{CVSROOT/modules} in the GCC CVS repository should be updated.
@end itemize

@menu
* Front End Directory::  The front end @file{@var{language}} directory.
* Front End Config::     The front end @file{config-lang.in} file.
@end menu

@node Front End Directory
@subsubsection The Front End @file{@var{language}} Directory

A front end @file{@var{language}} directory contains the source files
of that front end (but not of any runtime libraries, which should be
outside the @file{gcc} directory).  This includes documentation, and
possibly some subsidiary programs build alongside the front end.
Certain files are special and other parts of the compiler depend on
their names:

@table @file
@item config-lang.in
This file is required in all language subdirectories.  @xref{Front End
Config, , The Front End @file{config-lang.in} File}, for details of
its contents
@item Make-lang.in
This file is required in all language subdirectories.  It contains
targets @code{@var{lang}.@var{hook}} (where @code{@var{lang}} is the
setting of @code{language} in @file{config-lang.in}) for the following
values of @code{@var{hook}}, and any other Makefile rules required to
build those targets (which may if necessary use other Makefiles
specified in @code{outputs} in @file{config-lang.in}, although this is
deprecated).

@table @code
@item all.build
@itemx all.cross
@itemx start.encap
@itemx rest.encap
FIXME: exactly what goes in each of these targets?
@item info
Build info documentation for the front end, in the source directory.
This target is only called by @command{make bootstrap} if a suitable
version of @command{makeinfo} is available, so does not need to check
for this, and should fail if an error occurs.
@item dvi
Build DVI documentation for the front end, in the build directory.
This should be done using @code{$(TEXI2DVI)}, with appropriate
@option{-I} arguments pointing to directories of included files.
@item generated-manpages
Build generated man pages for the front end from Texinfo manuals
(@pxref{Man Page Generation}), in the source directory.  This target
is only called if the necessary tools are available, but should ignore
errors so as not to stop the build if errors occur; man pages are
optional and the tools involved may be installed in a broken way.
@item install-normal
FIXME: what is this target for?
@item install-common
Install everything that is part of the front end, apart from the
compiler executables listed in @code{compilers} in
@file{config-lang.in} that are installed in @file{@var{libsubdir}} by
the main @file{Makefile}.
@item install-info
Install info documentation for the front end, if it is present in the
source directory.  (It may not be present if a suitable version of
@command{makeinfo} was not installed.)  This target should run the
command @command{install-info} to update the info directory, but
should ignore errors when running that command.
@item install-man
Install man pages for the front end.  This target should ignore
errors.
@item uninstall
Uninstall files installed by installing the compiler.  This is
currently documented not to be supported, so the hook need not do
anything.
@item mostlyclean
@itemx clean
@itemx distclean
@itemx extraclean
@itemx maintainer-clean
Except for @code{extraclean}, the language parts of the standard GNU
@samp{*clean} targets. @xref{Standard Targets, , Standard Targets for
Users, standards, GNU Coding Standards}, for details of the standard
targets.  @code{extraclean} does @code{distclean} and also deletes
anything likely to be found in the source directory that shouldn't be
in the distribution.  For GCC, @code{maintainer-clean} should delete
all generated files in the source directory that are not checked into
CVS, but should not delete anything checked into CVS@.
@item stage1
@itemx stage2
@itemx stage3
@itemx stage4
Move to the stage directory files not included in @code{stagestuff} in
@file{config-lang.in} or otherwise moved by the main @file{Makefile}.
@end table

@item lang-options.h
This file provides entries for @code{documented_lang_options} in
@file{toplev.c} describing command-line options the front end accepts
for @option{--help} output.
@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 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.in} (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 stage 1 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 should
be installed in @file{@var{libsubdir}}.  The names here will each end
with @samp{\$(exeext)}.
@item stagestuff
If defined, a space-separated list of files that should be moved to
the @file{stage@var{n}} directories in each stage of bootstrap.
@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
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 Back End
@subsection Anatomy of a Target Back End

A back end for a target architecture in GCC has the following parts:

@itemize @bullet
@item
A directory @file{@var{machine}} under @file{gcc/config}, containing a
machine description @file{@var{machine}.md} file (@pxref{Machine Desc,
, Machine Descriptions}), header files @file{@var{machine}.h} and
@file{@var{machine}-protos.h} and a source file @file{@var{machine}.c}
(@pxref{Target Macros, , Target Description Macros and Functions}),
possibly a target Makefile fragment @file{t-@var{machine}}
(@pxref{Target Fragment, , The Target Makefile Fragment}), and maybe
some other files.  The names of these files may be changed from the
defaults given by explicit specifications in @file{config.gcc}.
@item
If necessary, a file @file{@var{machine}-modes.def} in the
@file{@var{machine}} directory, containing additional machine modes to
represent condition codes.  @xref{Condition Code}, for further details.
@item
Entries in @file{config.gcc} (@pxref{System Config, , The
@file{config.gcc} File}) for the systems with this target
architecture.
@item
Documentation in @file{gcc/doc/invoke.texi} for any command-line
options supported by this target (@pxref{Run-time Target, , Run-time
Target Specification}).  This means both entries in the summary table
of options and details of the individual options.
@item
Documentation in @file{gcc/doc/extend.texi} for any target-specific
attributes supported (@pxref{Target Attributes, , Defining
target-specific uses of @code{__attribute__}}), including where the
same attribute is already supported on some targets, which are
enumerated in the manual.
@item
Documentation in @file{gcc/doc/extend.texi} for any target-specific
pragmas supported.
@item
Documentation in @file{gcc/doc/extend.texi} of any target-specific
built-in functions supported.
@item
Documentation in @file{gcc/doc/md.texi} of any target-specific
constraint letters (@pxref{Machine Constraints, , Constraints for
Particular Machines}).
@item
A note in @file{gcc/doc/contrib.texi} under the person or people who
contributed the target support.
@item
Entries in @file{gcc/doc/install.texi} for all target triplets
supported with this target architecture, giving details of any special
notes about installation for this target, or saying that there are no
special notes if there are none.
@item
Possibly other support outside the @file{gcc} directory for runtime
libraries.  FIXME: reference docs for this.  The libstdc++ porting
manual needs to be installed as info for this to work, or to be a
chapter of this manual.
@end itemize

If the back end is added to the official GCC CVS repository, the
following are also necessary:

@itemize @bullet
@item
An entry for the target architecture in @file{readings.html} on the
GCC web site, with any relevant links.
@item
A news item about the contribution of support for that target
architecture, in @file{index.html} on the GCC web site.
@item
Normally, one or more maintainers of that target listed in
@file{MAINTAINERS}.  Some existing architectures may be unmaintained,
but it would be unusual to add support for a target that does not have
a maintainer when support is added.
@end itemize

@node Test Suites
@section Test Suites

GCC contains several test suites to help maintain compiler quality.
Most of the runtime libraries and language front ends in GCC have test
suites.  Currently only the C language test suites are documented
here; FIXME: document the others.

@menu
* Test Idioms::  Idioms used in test suite code.
* C Tests::      The C language test suites.
@end menu

@node Test Idioms
@subsection Idioms Used in Test Suite Code

In the @file{gcc.c-torture} test suites, test cases are commonly named
after the date on which they were added.  This allows people to tell
at a glance whether a test failure is because of a recently found bug
that has not yet been fixed, or whether it may be a regression.  In
other test suites, more descriptive names are used.  In general C test
cases have a trailing @file{-@var{n}.c}, starting with @file{-1.c}, in
case other test cases with similar names are added later.

Test cases should use @code{abort ()} to indicate failure and
@code{exit (0)} for success; on some targets these may be redefined to
indicate failure and success in other ways.

In the @file{gcc.dg} test suite, it is often necessary to test that an
error is indeed a hard error and not just a warning---for example,
where it is a constraint violation in the C standard, which must
become an error with @option{-pedantic-errors}.  The following idiom,
where the first line shown is line @var{line} of the file and the line
that generates the error, is used for this:

@smallexample
/* @{ dg-bogus "warning" "warning in place of error" @} */
/* @{ dg-error "@var{regexp}" "@var{message}" @{ target *-*-* @} @var{line} @} */
@end smallexample

It may be necessary to check that an expression is an integer constant
expression and has a certain value.  To check that @code{@var{E}} has
value @code{@var{V}}, an idiom similar to the following is used:

@smallexample
char x[((E) == (V) ? 1 : -1)];
@end smallexample

In @file{gcc.dg} tests, @code{__typeof__} is sometimes used to make
assertions about the types of expressions.  See, for example,
@file{gcc.dg/c99-condexpr-1.c}.  The more subtle uses depend on the
exact rules for the types of conditional expressions in the C
standard; see, for example, @file{gcc.dg/c99-intconst-1.c}.

It is useful to be able to test that optimizations are being made
properly.  This cannot be done in all cases, but it can be done where
the optimization will lead to code being optimized away (for example,
where flow analysis or alias analysis should show that certain code
cannot be called) or to functions not being called because they have
been expanded as built-in functions.  Such tests go in
@file{gcc.c-torture/execute}.  Where code should be optimized away, a
call to a nonexistent function such as @code{link_failure ()} may be
inserted; a definition

@smallexample
#ifndef __OPTIMIZE__
void
link_failure (void)
@{
  abort ();
@}
#endif
@end smallexample

@noindent
will also be needed so that linking still succeeds when the test is
run without optimization.  When all calls to a built-in function
should have been optimized and no calls to the non-built-in version of
the function should remain, that function may be defined as
@code{static} to call @code{abort ()} (although redeclaring a function
as static may not work on all targets).

FIXME: discuss non-C test suites here.

@node C Tests
@subsection C Language Test Suites

GCC contains the following C language test suites, in the
@file{gcc/testsuite} directory:

@table @file
@item gcc.c-torture/compat
FIXME: describe this.

This directory should probably not be used for new tests.
@item gcc.c-torture/compile
This test suite contains test cases that should compile, but do not
need to link or run.  These test cases are compiled with several
different combinations of optimization options.  All warnings are
disabled for these test cases, so this directory is not suitable if
you wish to test for the presence or absence of compiler warnings.
While special options can be set, and tests disabled on specific
platforms, by the use of @file{.x} files, mostly these test cases
should not contain platform dependencies.  FIXME: discuss how defines
such as @code{NO_LABEL_VALUES} and @code{STACK_SIZE} are used.
@item gcc.c-torture/execute
This test suite contains test cases that should compile, link and run;
otherwise the same comments as for @file{gcc.c-torture/compile} apply.
@item gcc.c-torture/unsorted
FIXME: describe this.

This directory should probably not be used for new tests.
@item gcc.dg
This test suite contains tests using the more modern @samp{dg} harness.
Magic comments determine whether the file is preprocessed, compiled,
linked or run.  In these tests, error and warning message texts are
compared against expected texts or regular expressions given in
comments.  These tests are run with the options @samp{-ansi -pedantic}
unless other options are given in the test.  Except as noted below they
are not run with multiple optimization options.
@item gcc.dg/cpp
This subdirectory contains tests of the preprocessor.
@item gcc.dg/debug
This subdirectory contains tests for debug formats.  Tests in this
subdirectory are run for each debug format that the compiler supports.
@item gcc.dg/format
This subdirectory contains tests of the @option{-Wformat} format
checking.  Tests in this directory are run with and without
@option{-DWIDE}.
@item gcc.dg/noncompile
This subdirectory contains tests of code that should not compile and
does not need any special compilation options.  They are run with
multiple optimization options, since sometimes invalid code crashes
the compiler with optimization.
@item gcc.dg/special
FIXME: describe this.
@item gcc.c-torture/misc-tests
FIXME: describe this, when it should be used for new tests and when it
shouldn't.
@end table

FIXME: merge in @file{testsuite/README.gcc} and discuss the format of
test cases and magic comments more.