HACKING

GNU M4
******

1. Introduction
===============

This file attempts to describe the processes we use to maintain M4,
and is not part of a release distribution.


2. Maintenance Notes
====================

* If you incorporate a change from somebody on the net:
  If it is a large change, you must make sure they have signed the
  appropriate paperwork, and be sure to add their name and email
  address to THANKS.  AUTHORS is built from the FSF list of copyright
  assignments, on fencepost.gnu.org.

* If somebody reports a new bug, write a test case, then mention his
  name in the ChangeLog entry.

* The correct response to most actual bugs is to write a new test case
  which demonstrates the bug.  Then fix the bug, re-run the test suite,
  and check everything in.

* Changes with user-visible effects must be mentioned in NEWS.

* New macros must be blind, or else prefixed with `m4' or `__', in
  order to minimize backward compatibility issues with previous
  releases of M4 when processing English text.

* GNU Coding Standards should be followed:
    http://www.gnu.org/prep/standards/
  Additionally, while GNU M4 is not yet POSIX compliant, we are trying
  to get closer to it (although some design decisions state that POSIX
  compliance should only happen when POSIXLY_CORRECT is in the
  environment or the -G option was passed on the command line):
    http://www.opengroup.org/onlinepubs/009695399/utilities/m4.html

* Except for third-party files (libtool, gnulib, ...), all .c files
  should #include <config.h> before anything else (since there are some
  #defines in config.h that potentially impact system headers, such as
  when the user does ./configure --disable-assert).  This means that no
  .h files need to #include <config.h>.  However, users compiling
  external modules should be able to compile without <config.h>, since
  <config.h> is specific to the M4 build and is not installable.


3. Bootstrapping
================

* The master M4 repository is stored in git.  You can obtain a read-only
  copy with:
    git clone git://git.sv.gnu.org/m4.git
  or
    cvs -d:pserver:anonymous@pserver.git.sv.gnu.org:/srv/git/m4.git \
      co -d m4 HEAD

  If you are a member of the savannah group for M4, a read-write
  copy can be obtained by:
    git clone <savannah-user>@git.sv.gnu.org:/srv/git/m4.git

* Before you can build from git, you need to bootstrap.  This requires:
  - A pre-installed version of GNU M4 1.4.5 or later, built from a
    package (recommend 1.4.13 or later)
  - A git checkout of Autoconf (2.63b-41 or later)
  - Automake 1.10b or later
  - Libtool 2.2 or later
  - Gettext 0.16 or later
  - Gperf 3.0 or later
  - Help2man 1.29 or later
  - Xz 4.999.8beta or later (from <http://tukaani.org/xz/>)
  - Texinfo 4.8 or later
  - Any prerequisites of the above (such as perl, tex)

  Note that none of these bootstrapping dependencies should be required
  by a distributed release.

* M4 includes gnulib as a git submodule.  By default, the bootstrap
  script will attempt to run
    git submodule update --init
  to grab a gnulib clone from the official read-only location of
    git://git.sv.gnu.org/gnulib.git

  However, this can be network and disk intensive.  If you already have
  another gnulib clone on your disk, you can use the environment
  variable GNULIB_SRCDIR to point to the previous checkout to speed up
  the process.  Additionally, both the bootstrap script and gnulib-tool
  require a shell that supports functions, so you can set the
  environment variable CONFIG_SHELL to choose a better shell on systems
  (like Solaris) where /bin/sh is lacking.  Thus, you may find it
  convenient to run:
    GNULIB_SRCDIR=path/to/gnulib CONFIG_SHELL=path/to/sh \
      path/to/sh ./bootstrap

  A read-only copy of gnulib can be obtained by:
      git clone git://git.sv.gnu.org/gnulib.git
    or
      cvs -d:pserver:anonymous@pserver.git.sv.gnu.org:/srv/git/gnulib.git \
        co -d gnulib HEAD

  Using a CVS checkout might work, but it is relatively untested,
  particularly now that we use a git submodule for gnulib.

  If you are a member of the savannah group for gnulib, a read-write
  copy can be obtained by:
    git clone <savannah-user>@git.sv.gnu.org:/srv/git/gnulib.git

  If you are behind a firewall that blocks the git protocol, you may
  find it useful to do:
    git config --global url.http://git.savannah.gnu.org/r/.insteadof \
      git://git.sv.gnu.org/
  to force git to transparently rewrite all savannah git references to
  instead use http.

* Either add the gnulib directory to your PATH, or run
    GNULIB_TOOL=path/to/gnulib/gnulib-tool ./bootstrap

* When it is time for a release, it is a good idea to bootstrap with
  official releases of the autotools, rather than git builds, to reduce
  the pain of a user re-running bootstrap on the packaged M4.  However,
  files installed by Automake should be updated to the latest version
  from their respective upstream source, rather than the version that
  shipped with the automake release.

* Normally, after running bootstrap, 'git status' should not show any
  differences; if things changed, please provide a patch or at least
  report it as a bug.  One case where things are changed is if the
  gnulib submodule comes from an older date than the current installed
  libtool, such that libtoolize will replace the symlinks to an older
  version of build-aux files with their newer counterpart; the fix to
  this is updating the submodule to a newer gnulib version.

* If you would like to check that you are not missing out on any useful
  gnulib modules, comment out the gl_ASSERT_NO_GNULIB_POSIXCHECK in
  configure.ac, then run 'make CFLAGS='-DGNULIB_POSIXCHECK=1' with gcc,
  and look at the resulting warnings.


4. Test Suite
=============

* Use
    make check
  liberally, on as many platforms as you can.  Use as many compilers and
  linkers you can.

* Some of the testsuite is generated from the documentation.
  All instances of @example in doc/m4.texinfo that are not preceeded by
  "@comment ignore" are turned into tests in the tests directory.


5. Editing 'ChangeLog'
======================

* When in doubt, check that emacs can syntax-color properly in
  change-log-mode.  And preferably use emacs 'C-x 4 a'
  (add-change-log-entry-other-window) to open ChangeLog with an
  appropriate new template.

* If this change is by a different author, or on a different date to the
  last entry start a new entry at the top of the file with the format
  (note two spaces between each field):

yyyy-mm-dd  Name of Author  <email@address>

*  If more than one person collaborated on the change, additional
   authors can be listed on subsequent lines, thus:

yyyy-mm-dd  Name of Main Author  <email@address>,
            Name of Contributor  <another@email.address>

* Where a change author did not supply a copyright assignment, but the
  changes they submitted were sufficiently trivial to commit in any case
  (see the GCS for guidelines on this), then flag this against their
  name in the header, thus:

yyyy-mm-dd  Name of Author  <email@address>  (tiny change)

* Preferably the next part should be a description of the overall
  purpose of the change, separated from the header by a blank line,
  indented by 1 tab, and filled at column 72.  The last character of the
  description should be a colon, :.

* Changes to each file come next.  Each new file starts on a new line,
  indented by 1 tab and starting with an asterisk and a space.  Multiple
  files can be listed here relative to $top_srcdir, and comma separated.
  Names of functions (or sections as appropriate) to which the change
  applies should be named inside parentheses and comma separated.  If
  this goes beyond column 72, then parens should be closed and re-opened
  on the next line:

	* file, another/file, test/testcases/foo.test (func_foo)
	(func_bar, func_baz): Description of changes.

* If the change does not apply to particular functions (or sections),
  the section list can be omitted:

	* file, another/file, test/testcases/foo.test: General changes.

* If the changes are particular to certain architectures, they should be
  listed after the functions in square brackets:

	* file, another/file (func_foo) [linux, solaris]: Description of
	changes.

* Subsequent changes in other files that are related to the same overall
  enhancement or bugfix should be listed concurrently, without blank
  lines.  Always start a fresh line for a new file:

	* file, another/file (func_foo) [linux, solaris]: Description of
	changes.
	* doc/foo.texi (Invoking Foo): Document.
	* NEWS: Updated.

* If the change is in response to a problem reported by someone other
  than the author, then credit them at the end of the description with:

	Reported by Reporter Name <email@address>.

* See the GNU Coding Standards document for more details on ChangeLog
  formatting.

6. Formatting
=============

* Use space-only indentation in nearly all files (Makefile and
  ChangeLogs being the exception).

  If you use Emacs and your m4 working directory name matches,
  this code in your ~/.emacs enables the right mode:

  ;; In m4, indent with spaces everywhere (not TABs).
  ;; Exceptions: Makefile and ChangeLog modes.
  (add-hook 'find-file-hook '(lambda ()
    (if (and buffer-file-name
             (string-match "/m4\\>" (buffer-file-name))
             (not (string-equal mode-name "Change Log"))
             (not (string-equal mode-name "Makefile")))
        (setq indent-tabs-mode nil))))

* Since the source code was massively converted from tabs in December
  2009, you may find it helpful to use 'git diff -w' and 'git blame -w'
  helpful for overlooking the whitespace changes.

* Avoid #ifdefs inside function bodies, whenever possible.  If you
  encounter a portability issue, it is better to propose a gnulib module
  that works around it, and have m4 use that module.


7. Release Procedure
====================

* If you are an m4 maintainer, but have not yet registered your
  gpg public key and (preferred) email address with the FSF, send an
  email, preferably GPG-signed, to <ftp-upload@gnu.org> that includes
  the following:

    (a) name of package(s) that you are the maintainer for, and your
        preferred email address.

    (b) an ASCII armored copy of your GnuPG key, as an attachment.
        ("gpg --export -a YOUR_KEY_ID > mykey.asc" should give you
        this.)

  When you have received acknowledgement of your message, the proper GPG
  keys will be registered on ftp-upload.gnu.org and only then will you be
  authorized to upload files to the FSF ftp machines.

* If you do not have access to the mailing list administrative interface,
  approach the list owners for the password.  Be sure to check the lists
  (esp. bug-m4) for outstanding bug reports also in the list of
  pending moderation requests.  This step is not strictly necessary, but
  helps, since by default, m4-announce rejects all posts, so you have to
  get an administrator to allow your announcement through.

* Make sure you have rsync installed.

* Make sure you have GNU make installed.

* Make sure you have an up-to-date version of help2man installed.

* Make sure your locale is sane, e.g. by exporting LC_ALL=C.

* Make sure you are happy with the particular gnulib version recorded as
  the gnulib submodule.  If necessary to update to the latest, run:
    git submodule foreach git pull origin master
    git commit -m 'Update gnulib submodule to latest.' gnulib
  In particular, ensure that the gnulib version is at least as new as
  the latest stable libtool release.

* Update the version number in NEWS and ChangeLog, and mention in README
  whether the release is stable.  See
  http://www.gnu.org/software/libtool/contribute.html for details of the
  numbering scheme (M4 uses a similar scheme to libtool, although
  intra-release versions carry more information thanks to
  git-version-gen).

* Run ./bootstrap, perhaps with environment variables set.

* Run ./configure (a VPATH build should work, but is less tested).

* Run `make'.  The file doc/m4.1 needs to exist for a distribution, and
  be up-to-date with m4 --help output, but `make dist' intentionally
  does not depend on running a built binary.

* Run `git commit' from the source tree if there are any changes from
  the previous steps.

* Run `git tag -s -m <version> -u <gpg_key> v<version>' with the desired
  version number.  Do not push anything upstream at this point.

* Run `make distcheck'.  If there are any problems, fix them, then run
  `git tag -d v<version>' and start again from the `git commit' step.

* Run `make <target>', with target set to `stable', `alpha', or `beta'
  as appropriate.  This will run various additional checks.

* Run './build-aux/gnupload --to [dest].gnu.org:m4 [files]' to create
  detached gpg signature and clear signed directive files, and upload
  the combination to the correct location.  For an alpha release,
  gnupload will place files in alpha.gnu.org, in /incoming/alpha; for a
  full release, gnupload will place files in ftp.gnu.org, in
  /incoming/ftp.  Verify that the files uploaded successfully before
  sending an announcement.

* Send announcement to m4-discuss@gnu.org, m4-announce@gnu.org, and
  autotools-announce@gnu.org.  If not an alpha send to info-gnu@gnu.org
  as well.  Use gnulib/build-aux/announce-gen to form an initial
  template for the announcement (you may also need to install the perl
  module Digest::SHA1).  Contact a list administrator for m4-announce in
  advance to ensure your post will make it through (the list is normally
  set to silently discard all posts, even from subscribers).

* Update version number in configure.ac to next alpha number.
  See http://www.gnu.org/software/libtool/contribute.html for details of
  the numbering scheme.

* Update NEWS, README, and ChangeLog to start the intra-release changes,
  and run `git commit'.  Then run `git push origin refs/tags/v<version>'
  to push the release tag and complete the release.

* For stable releases, update the webpages.
  Run `build-aux/gnu-web-doc-update', which runs `make web-manual' on a
  temporary git branch corresponding to the release, then copies the
  contents of doc/manual into a CVS checkout of the M4 manual
  repository.  Follow up with any needed edits to m4.html, using:
    export CVS_RSH=ssh
    cvs -z3 -d:ext:<user>@cvs.savannah.gnu.org:/web/m4 co m4

* Update the Free Software Directory.  Browse to:
    http://directory.fsf.org/project/m4/
  and send an email to <bug-directory@gnu.org> mentioning any content
  that needs to be updated.

-----------
Copyright (C) 2004-2010, 2013-2014, 2017 Free Software Foundation, Inc.

The canonical source of this file is maintained with the
GNU M4 package.  Report bugs to bug-m4@gnu.org.

GNU M4 is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

GNU M4 is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.

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