2013-05-03 14:25:37 +00:00
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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2009-06-29 11:09:17 +00:00
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<body>
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<h1>Contributor guidelines</h1>
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<ul id="toc"></ul>
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<h2><a name="patches">General tips for contributing patches</a></h2>
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<ol>
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2017-01-04 11:14:13 +00:00
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<li>
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<p>Discuss any large changes on the mailing list first. Post patches
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early and listen to feedback.</p>
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</li>
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2009-06-29 11:09:17 +00:00
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2017-01-04 11:14:13 +00:00
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<li>
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<p>Official upstream repository is kept in git
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2014-10-21 10:20:56 +00:00
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(<code>git://libvirt.org/libvirt.git</code>) and is browsable
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along with other libvirt-related repositories
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2017-01-04 11:14:13 +00:00
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(e.g. libvirt-python) <a href="http://libvirt.org/git/">online</a>.</p>
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</li>
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2014-10-21 10:20:56 +00:00
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2017-01-04 11:14:13 +00:00
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<li>
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<p>Patches to translations are maintained via
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2015-05-27 14:42:30 +00:00
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the <a href="https://fedora.zanata.org/">zanata project</a>.
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If you want to fix a translation in a .po file, join the
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appropriate language team. The libvirt release process
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automatically pulls the latest version of each translation
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2017-01-04 11:14:13 +00:00
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file from zanata.</p>
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</li>
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2015-05-27 14:42:30 +00:00
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2017-06-15 03:25:31 +00:00
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<li><p>Post patches using <code>git send-email</code>, with git
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rename detection enabled. You need a one-time setup of:</p>
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2013-01-11 00:39:04 +00:00
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<pre>
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git config diff.renames true
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2010-11-12 14:33:00 +00:00
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</pre>
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2013-01-11 00:39:04 +00:00
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<p>Also, for code motion patches, you may find that <code>git
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diff --patience</code> provides an easier-to-read patch.
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However, the usual workflow of libvirt developer is:</p>
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2012-07-09 08:01:21 +00:00
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<pre>
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git checkout master
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git pull
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git checkout -t origin -b workbranch
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Hack, committing any changes along the way
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</pre>
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2013-07-03 20:43:11 +00:00
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<p>More hints on compiling can be
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found <a href="compiling.html">here</a>. When you want to
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post your patches:</p>
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2012-07-09 08:01:21 +00:00
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<pre>
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git pull --rebase
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(fix any conflicts)
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2012-09-06 17:21:21 +00:00
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git send-email --cover-letter --no-chain-reply-to --annotate \
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2017-06-15 03:25:31 +00:00
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--confirm=always --to=libvir-list@redhat.com master
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2012-07-09 08:01:21 +00:00
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</pre>
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2017-06-15 03:25:31 +00:00
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<p>For a single patch you can omit
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2012-09-06 17:21:21 +00:00
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<code>--cover-letter</code>, but a series of two or more
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2017-06-15 03:25:31 +00:00
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patches needs a cover letter.</p>
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<p>Note that the <code>git send-email</code> subcommand may not
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be in the main git package and using it may require installation
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of a separate package, for example the "git-email" package in
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Fedora and Debian. If this is your first time using
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<code>git send-email</code>, you might need to configure it to
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point it to your SMTP server with something like:</p>
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<pre>
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git config --global sendemail.smtpServer stmp.youremailprovider.net
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</pre>
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<p>If you get tired of typing
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<code>--to=libvir-list@redhat.com</code> all the time, you can
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configure that to be automatically handled as well:</p>
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2012-07-09 08:01:21 +00:00
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<pre>
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git config sendemail.to libvir-list@redhat.com
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</pre>
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2017-06-15 03:25:31 +00:00
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<p>As a rule, patches should be sent to the mailing list only: all
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developers are subscribed to libvir-list and read it regularly, so
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please don't CC individual developers unless they've explicitly
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asked you to.</p>
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<p>Avoid using mail clients for sending patches, as most of them
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will mangle the messages in some way, making them unusable for our
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purposes. Gmail and other Web-based mail clients are particularly
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bad at this.</p>
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<p>If everything went well, your patch should show up on the
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<a href="https://www.redhat.com/archives/libvir-list/">libvir-list
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archives</a> in a matter of minutes; if you still can't find it on
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there after an hour or so, you should double-check your setup. Note
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that your very first post to the mailing list will be subject to
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moderation, and it's not uncommon for that to take around a day.</p>
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2012-07-09 08:01:21 +00:00
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<p>Please follow this as close as you can, especially the rebase and
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2017-06-15 03:25:31 +00:00
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<code>git send-email</code> part, as it makes life easier for other
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developers to review your patch set.</p>
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<p>One should avoid sending patches as attachments,
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2012-07-09 08:01:21 +00:00
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but rather send them in email body along with commit message. If a
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developer is sending another version of the patch (e.g. to address
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2014-12-08 13:13:00 +00:00
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review comments), they are advised to note differences to previous
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2012-07-09 08:01:21 +00:00
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versions after the <code>---</code> line in the patch so that it helps
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reviewers but doesn't become part of git history. Moreover, such patch
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needs to be prefixed correctly with
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<code>--subject-prefix=PATCHv2</code> appended to <code>git
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send-email</code> (substitute <code>v2</code> with the correct
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version if needed though).</p>
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</li>
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2013-01-04 17:27:16 +00:00
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<li><p>In your commit message, make the summary line reasonably
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short (60 characters is typical), followed by a blank line,
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followed by any longer description of why your patch makes
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sense. If the patch fixes a regression, and you know what
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commit introduced the problem, mentioning that is useful.
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If the patch resolves a bugzilla report, mentioning the URL
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of the bug number is useful; but also summarize the issue
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rather than making all readers follow the link. You can use
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'git shortlog -30' to get an idea of typical summary lines.
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Libvirt does not currently attach any meaning to
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Signed-off-by: lines, so it is up to you if you want to
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include or omit them in the commit message.
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</p>
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</li>
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2012-07-09 08:01:21 +00:00
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<li><p>Split large changes into a series of smaller patches,
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2012-09-06 17:21:21 +00:00
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self-contained if possible, with an explanation of each patch
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and an explanation of how the sequence of patches fits
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together. Moreover, please keep in mind that it's required to
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be able to compile cleanly (<b>including</b> <code>make
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check</code> and <code>make syntax-check</code>) after each
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patch. A feature does not have to work until the end of a
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series, but intermediate patches must compile and not cause
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test-suite failures (this is to preserve the usefulness
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of <code>git bisect</code>, among other things).</p>
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2010-04-15 17:31:04 +00:00
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</li>
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2012-07-09 08:01:21 +00:00
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2017-01-04 11:14:13 +00:00
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<li>
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<p>Make sure your patches apply against libvirt GIT. Developers
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only follow GIT and don't care much about released versions.</p>
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</li>
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2009-06-29 11:09:17 +00:00
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<li><p>Run the automated tests on your code before submitting any changes.
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2012-09-24 23:44:34 +00:00
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In particular, configure with compile warnings set to
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-Werror. This is done automatically for a git checkout; from a
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tarball, use:</p>
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2010-11-12 14:33:00 +00:00
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<pre>
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2012-09-24 23:44:34 +00:00
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./configure --enable-werror
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2010-11-12 14:33:00 +00:00
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</pre>
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2009-11-06 15:04:19 +00:00
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<p>
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and run the tests:
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</p>
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2010-11-12 14:33:00 +00:00
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<pre>
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2009-06-29 11:09:17 +00:00
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make check
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make syntax-check
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2010-11-12 14:33:00 +00:00
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make -C tests valgrind
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</pre>
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2013-02-05 15:03:56 +00:00
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<p><a href="http://valgrind.org/">Valgrind</a> is a test that checks
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for memory management issues, such as leaks or use of uninitialized
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variables.
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2009-11-06 15:04:19 +00:00
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</p>
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2009-06-29 11:09:17 +00:00
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build: add configure option to disable gnulib tests
The gnulib testsuite is relatively stable - the only times it is
likely to have a test change from pass to fail is on a gnulib
submodule update or a major system change (such as moving from
Fedora 18 to 19, or other large change to libc). While it is an
important test for end users on arbitrary machines (to make sure
that the portability glue works for their machine), it mostly
wastes time for development testing (as most developers aren't
making any of the major changes that would cause gnulib tests
to alter behavior). Thus, it pays to make the tests optional
at configure time, defaulting to off for development, on for
tarballs, with autobuilders requesting it to be on. It also
helps to allow a make-time override, via VIR_TEST_EXPENSIVE=[01]
(much the way automake sets up V=[01] for overriding the configure
time default of how verbose to be).
Automake has some pretty hard-coded magic with regards to the
TESTS variable; I had quite a job figuring out how to keep
'make distcheck' passing regardless of the configure option
setting in use, while still disabling the tests at runtime
when I did not configure them on and did not use the override
variable. Thankfully, we require GNU make, which lets me
hide some information from Automake's magic handling of TESTS.
* bootstrap.conf (bootstrap_epilogue): Munge gnulib test variable.
* configure.ac (--enable-expensive-tests): Add new enable switch.
(VIR_TEST_EXPENSIVE_DEFAULT, WITH_EXPENSIVE_TESTS): Set new
witnesses.
* gnulib/tests/Makefile.am (TESTS): Make tests conditional on
configure settings and the VIR_TEST_EXPENSIVE variable.
* tests/Makefile.am (TESTS_ENVIRONMENT): Expose VIR_TEST_EXPENSIVE
to all tests.
* autobuild.sh: Enable all tests during autobuilds.
* libvirt.spec.in (%configure): Likewise.
* mingw-libvirt.spec.in (%mingw_configure): Likewise.
* docs/hacking.html.in: Document the option.
* HACKING: Regenerate.
Signed-off-by: Eric Blake <eblake@redhat.com>
2013-07-31 13:18:58 +00:00
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<p>
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Some tests are skipped by default in a development environment,
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based on the time they take in comparison to the likelihood
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that those tests will turn up problems during incremental builds.
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2014-06-10 09:18:02 +00:00
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These tests default to being run when building from a
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build: add configure option to disable gnulib tests
The gnulib testsuite is relatively stable - the only times it is
likely to have a test change from pass to fail is on a gnulib
submodule update or a major system change (such as moving from
Fedora 18 to 19, or other large change to libc). While it is an
important test for end users on arbitrary machines (to make sure
that the portability glue works for their machine), it mostly
wastes time for development testing (as most developers aren't
making any of the major changes that would cause gnulib tests
to alter behavior). Thus, it pays to make the tests optional
at configure time, defaulting to off for development, on for
tarballs, with autobuilders requesting it to be on. It also
helps to allow a make-time override, via VIR_TEST_EXPENSIVE=[01]
(much the way automake sets up V=[01] for overriding the configure
time default of how verbose to be).
Automake has some pretty hard-coded magic with regards to the
TESTS variable; I had quite a job figuring out how to keep
'make distcheck' passing regardless of the configure option
setting in use, while still disabling the tests at runtime
when I did not configure them on and did not use the override
variable. Thankfully, we require GNU make, which lets me
hide some information from Automake's magic handling of TESTS.
* bootstrap.conf (bootstrap_epilogue): Munge gnulib test variable.
* configure.ac (--enable-expensive-tests): Add new enable switch.
(VIR_TEST_EXPENSIVE_DEFAULT, WITH_EXPENSIVE_TESTS): Set new
witnesses.
* gnulib/tests/Makefile.am (TESTS): Make tests conditional on
configure settings and the VIR_TEST_EXPENSIVE variable.
* tests/Makefile.am (TESTS_ENVIRONMENT): Expose VIR_TEST_EXPENSIVE
to all tests.
* autobuild.sh: Enable all tests during autobuilds.
* libvirt.spec.in (%configure): Likewise.
* mingw-libvirt.spec.in (%mingw_configure): Likewise.
* docs/hacking.html.in: Document the option.
* HACKING: Regenerate.
Signed-off-by: Eric Blake <eblake@redhat.com>
2013-07-31 13:18:58 +00:00
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tarball or with the configure option --enable-expensive-tests;
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you can also force a one-time toggle of these tests by
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setting VIR_TEST_EXPENSIVE to 0 or 1 at make time, as in:
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</p>
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<pre>
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make check VIR_TEST_EXPENSIVE=1
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</pre>
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2010-11-12 14:33:00 +00:00
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<p>
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If you encounter any failing tests, the VIR_TEST_DEBUG
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environment variable may provide extra information to debug
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the failures. Larger values of VIR_TEST_DEBUG may provide
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larger amounts of information:
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</p>
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2010-03-08 15:26:30 +00:00
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2010-11-12 14:33:00 +00:00
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<pre>
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2010-03-08 15:26:30 +00:00
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VIR_TEST_DEBUG=1 make check (or)
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2010-11-12 14:33:00 +00:00
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VIR_TEST_DEBUG=2 make check
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</pre>
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2013-08-13 02:40:54 +00:00
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<p>
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When debugging failures during development, it is possible
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to focus in on just the failing subtests by using TESTS and
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VIR_TEST_RANGE:
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</p>
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<pre>
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make check VIR_TEST_DEBUG=1 VIR_TEST_RANGE=3-5 TESTS=qemuxml2argvtest
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</pre>
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2010-11-12 14:33:00 +00:00
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<p>
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Also, individual tests can be run from inside the <code>tests/</code>
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directory, like:
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</p>
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<pre>
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./qemuxml2xmltest
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</pre>
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2015-04-23 18:02:57 +00:00
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<p>
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If you are adding new test cases, or making changes that alter
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existing test output, you can use the environment variable
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VIR_TEST_REGENERATE_OUTPUT to quickly update the saved test data.
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Of course you still need to review the changes VERY CAREFULLY to
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ensure they are correct.
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</p>
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<pre>
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VIR_TEST_REGENERATE_OUTPUT=1 ./qemuxml2argvtest
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</pre>
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2013-01-04 17:27:16 +00:00
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<p>There is also a <code>./run</code> script at the top level,
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to make it easier to run programs that have not yet been
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installed, as well as to wrap invocations of various tests
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2013-02-05 15:03:56 +00:00
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under gdb or Valgrind.
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</p>
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2016-04-18 12:10:33 +00:00
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<p>When running our test suite it may happen that the test result is
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nondeterministic because of the test suite relying on a particular file
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in the system being accessible or having some specific value. To catch
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this kind of errors, the test suite has a module for that prints any
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path touched that fulfils constraints described above
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into a file. To enable it just set
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<code>VIR_TEST_FILE_ACCESS</code> environment variable.
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Then <code>VIR_TEST_FILE_ACCESS_OUTPUT</code> environment
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variable can alter location where the file is stored.</p>
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<pre>
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VIR_TEST_FILE_ACCESS=1 VIR_TEST_FILE_ACCESS_OUTPUT="/tmp/file_access.txt" ./qemuxml2argvtest
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</pre>
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2013-02-05 15:03:56 +00:00
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</li>
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<li><p>The Valgrind test should produce similar output to
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<code>make check</code>. If the output has traces within libvirt
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API's, then investigation is required in order to determine the
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cause of the issue. Output such as the following indicates some
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sort of leak:
|
|
|
|
|
</p>
|
|
|
|
|
<pre>
|
|
|
|
|
==5414== 4 bytes in 1 blocks are definitely lost in loss record 3 of 89
|
|
|
|
|
==5414== at 0x4A0881C: malloc (vg_replace_malloc.c:270)
|
|
|
|
|
==5414== by 0x34DE0AAB85: xmlStrndup (in /usr/lib64/libxml2.so.2.7.8)
|
|
|
|
|
==5414== by 0x4CC97A6: virDomainVideoDefParseXML (domain_conf.c:7410)
|
|
|
|
|
==5414== by 0x4CD581D: virDomainDefParseXML (domain_conf.c:10188)
|
|
|
|
|
==5414== by 0x4CD8C73: virDomainDefParseNode (domain_conf.c:10640)
|
|
|
|
|
==5414== by 0x4CD8DDB: virDomainDefParse (domain_conf.c:10590)
|
|
|
|
|
==5414== by 0x41CB1D: testCompareXMLToArgvHelper (qemuxml2argvtest.c:100)
|
|
|
|
|
==5414== by 0x41E20F: virtTestRun (testutils.c:161)
|
|
|
|
|
==5414== by 0x41C7CB: mymain (qemuxml2argvtest.c:866)
|
|
|
|
|
==5414== by 0x41E84A: virtTestMain (testutils.c:723)
|
|
|
|
|
==5414== by 0x34D9021734: (below main) (in /usr/lib64/libc-2.15.so)
|
|
|
|
|
</pre>
|
|
|
|
|
<p>In this example, the <code>virDomainDefParseXML()</code> had
|
|
|
|
|
an error path where the <code>virDomainVideoDefPtr video</code>
|
|
|
|
|
pointer was not properly disposed. By simply adding a
|
|
|
|
|
<code>virDomainVideoDefFree(video);</code> in the error path,
|
|
|
|
|
the issue was resolved.
|
|
|
|
|
</p>
|
|
|
|
|
|
|
|
|
|
<p>Another common mistake is calling a printing function, such as
|
|
|
|
|
<code>VIR_DEBUG()</code> without initializing a variable to be
|
|
|
|
|
printed. The following example involved a call which could return
|
|
|
|
|
an error, but not set variables passed by reference to the call.
|
|
|
|
|
The solution was to initialize the variables prior to the call.
|
|
|
|
|
</p>
|
|
|
|
|
<pre>
|
|
|
|
|
==4749== Use of uninitialised value of size 8
|
|
|
|
|
==4749== at 0x34D904650B: _itoa_word (in /usr/lib64/libc-2.15.so)
|
|
|
|
|
==4749== by 0x34D9049118: vfprintf (in /usr/lib64/libc-2.15.so)
|
|
|
|
|
==4749== by 0x34D9108F60: __vasprintf_chk (in /usr/lib64/libc-2.15.so)
|
|
|
|
|
==4749== by 0x4CAEEF7: virVasprintf (stdio2.h:199)
|
|
|
|
|
==4749== by 0x4C8A55E: virLogVMessage (virlog.c:814)
|
|
|
|
|
==4749== by 0x4C8AA96: virLogMessage (virlog.c:751)
|
|
|
|
|
==4749== by 0x4DA0056: virNetTLSContextCheckCertKeyUsage (virnettlscontext.c:225)
|
|
|
|
|
==4749== by 0x4DA06DB: virNetTLSContextCheckCert (virnettlscontext.c:439)
|
|
|
|
|
==4749== by 0x4DA1620: virNetTLSContextNew (virnettlscontext.c:562)
|
|
|
|
|
==4749== by 0x4DA26FC: virNetTLSContextNewServer (virnettlscontext.c:927)
|
|
|
|
|
==4749== by 0x409C39: testTLSContextInit (virnettlscontexttest.c:467)
|
|
|
|
|
==4749== by 0x40AB8F: virtTestRun (testutils.c:161)
|
|
|
|
|
</pre>
|
|
|
|
|
<p>Valgrind will also find some false positives or code paths
|
|
|
|
|
which cannot be resolved by making changes to the libvirt code.
|
|
|
|
|
For these paths, it is possible to add a filter to avoid the
|
|
|
|
|
errors. For example:
|
|
|
|
|
</p>
|
|
|
|
|
<pre>
|
|
|
|
|
==4643== 7 bytes in 1 blocks are possibly lost in loss record 4 of 20
|
|
|
|
|
==4643== at 0x4A0881C: malloc (vg_replace_malloc.c:270)
|
|
|
|
|
==4643== by 0x34D90853F1: strdup (in /usr/lib64/libc-2.15.so)
|
|
|
|
|
==4643== by 0x34EEC2C08A: ??? (in /usr/lib64/libnl.so.1.1)
|
|
|
|
|
==4643== by 0x34EEC15B81: ??? (in /usr/lib64/libnl.so.1.1)
|
|
|
|
|
==4643== by 0x34D8C0EE15: call_init.part.0 (in /usr/lib64/ld-2.15.so)
|
|
|
|
|
==4643== by 0x34D8C0EECF: _dl_init (in /usr/lib64/ld-2.15.so)
|
|
|
|
|
==4643== by 0x34D8C01569: ??? (in /usr/lib64/ld-2.15.so)
|
|
|
|
|
|
|
|
|
|
</pre>
|
2013-07-30 08:21:11 +00:00
|
|
|
<p>In this instance, it is acceptable to modify the
|
2013-02-05 15:03:56 +00:00
|
|
|
<code>tests/.valgrind.supp</code> file in order to add a
|
|
|
|
|
suppression filter. The filter should be unique enough to
|
|
|
|
|
not suppress real leaks, but it should be generic enough to
|
|
|
|
|
cover multiple code paths. The format of the entry can be
|
|
|
|
|
found in the documentation found at the
|
2013-07-08 22:37:11 +00:00
|
|
|
<a href="http://valgrind.org/">Valgrind home page</a>.
|
2013-02-05 15:03:56 +00:00
|
|
|
The following trace was added to <code>tests/.valgrind.supp</code>
|
|
|
|
|
in order to suppress the warning:
|
|
|
|
|
</p>
|
|
|
|
|
<pre>
|
|
|
|
|
{
|
|
|
|
|
dlInitMemoryLeak1
|
|
|
|
|
Memcheck:Leak
|
|
|
|
|
fun:?alloc
|
|
|
|
|
...
|
|
|
|
|
fun:call_init.part.0
|
|
|
|
|
fun:_dl_init
|
|
|
|
|
...
|
|
|
|
|
obj:*/lib*/ld-2.*so*
|
|
|
|
|
}
|
|
|
|
|
</pre>
|
2010-04-15 17:31:04 +00:00
|
|
|
</li>
|
2017-01-04 12:53:59 +00:00
|
|
|
|
|
|
|
|
<li>
|
|
|
|
|
<p>Update tests and/or documentation, particularly if you are adding
|
|
|
|
|
a new feature or changing the output of a program.</p>
|
|
|
|
|
</li>
|
2017-01-04 11:45:23 +00:00
|
|
|
|
|
|
|
|
<li>
|
|
|
|
|
<p>Don't forget to update the <a href="news.html">release notes</a>
|
|
|
|
|
by changing <code>docs/news.xml</code> if your changes are
|
|
|
|
|
significant. All user-visible changes, such as adding new XML elements
|
|
|
|
|
or fixing all but the most obscure bugs, must be (briefly) described
|
|
|
|
|
in a release notes entry; changes that are only relevant to other
|
|
|
|
|
libvirt developers, such as code refactoring, don't belong in the
|
2017-02-03 09:19:12 +00:00
|
|
|
release notes. Note that <code>docs/news.xml</code> should be updated
|
|
|
|
|
in its own commit not to get in the way of backports.</p>
|
2017-01-04 11:45:23 +00:00
|
|
|
</li>
|
2009-06-29 11:09:17 +00:00
|
|
|
</ol>
|
|
|
|
|
|
|
|
|
|
<p>
|
|
|
|
|
There is more on this subject, including lots of links to background
|
|
|
|
|
reading on the subject, on
|
2014-07-04 14:12:47 +00:00
|
|
|
<a href="http://people.redhat.com/rjones/how-to-supply-code-to-open-source-projects/">
|
2013-07-08 22:37:11 +00:00
|
|
|
Richard Jones' guide to working with open source projects</a>.
|
2009-06-29 11:09:17 +00:00
|
|
|
</p>
|
|
|
|
|
|
2017-04-28 16:30:07 +00:00
|
|
|
<h2><a name="tooling">Tooling</a></h2>
|
|
|
|
|
|
|
|
|
|
<p>
|
|
|
|
|
libvirt includes support for some useful development tools right in its
|
|
|
|
|
source repository, meaning users will be able to take advantage of them
|
|
|
|
|
without little or no configuration. Examples include:
|
|
|
|
|
</p>
|
|
|
|
|
|
|
|
|
|
<ul>
|
|
|
|
|
<li>
|
|
|
|
|
<a href="https://github.com/jeaye/color_coded">color_coded</a>,
|
|
|
|
|
a vim plugin for libclang-powered semantic syntax highlighting;
|
|
|
|
|
</li>
|
|
|
|
|
|
|
|
|
|
<li>
|
|
|
|
|
<a href="http://valloric.github.io/YouCompleteMe/">YouCompleteMe</a>,
|
|
|
|
|
a vim plugin for libclang-powered semantic code completion.
|
|
|
|
|
</li>
|
|
|
|
|
</ul>
|
|
|
|
|
|
2017-03-03 09:46:16 +00:00
|
|
|
<h2><a name="naming">Naming conventions</a></h2>
|
|
|
|
|
|
|
|
|
|
<p>
|
|
|
|
|
When reading libvirt code, a number of different naming conventions will
|
|
|
|
|
be evident due to various changes in thinking over the course of the
|
|
|
|
|
project's lifetime. The conventions documented below should be followed
|
|
|
|
|
when creating any entirely new files in libvirt. When working on existing
|
|
|
|
|
files, while it is desirable to apply these conventions, keeping a
|
|
|
|
|
consistent style with existing code in that particular file is generally
|
|
|
|
|
more important. The overall guiding principal is that every file, enum,
|
|
|
|
|
struct, function, macro and typedef name must have a 'vir' or 'VIR' prefix.
|
|
|
|
|
All local scope variable names are exempt, and global variables are exempt,
|
|
|
|
|
unless exported in a header file.
|
|
|
|
|
</p>
|
|
|
|
|
|
|
|
|
|
<dl>
|
|
|
|
|
<dt>File names</dt>
|
|
|
|
|
<dd>
|
|
|
|
|
<p>
|
|
|
|
|
File naming varies depending on the subdirectory. The preferred
|
|
|
|
|
style is to have a 'vir' prefix, followed by a name which matches
|
|
|
|
|
the name of the functions / objects inside the file. For example,
|
|
|
|
|
a file containing an object 'virHashtable' is stored in files
|
|
|
|
|
'virhashtable.c' and 'virhashtable.h'. Sometimes, methods which
|
|
|
|
|
would otherwise be declared 'static' need to be exported for use
|
|
|
|
|
by a test suite. For this purpose a second header file should be
|
|
|
|
|
added with a suffix of 'priv', e.g. 'virhashtablepriv.h'. Use of
|
|
|
|
|
underscores in file names is discouraged when using the 'vir'
|
|
|
|
|
prefix style. The 'vir' prefix naming applies to src/util,
|
|
|
|
|
src/rpc and tests/ directories. Most other directories do not
|
|
|
|
|
follow this convention.
|
|
|
|
|
</p>
|
|
|
|
|
</dd>
|
|
|
|
|
<dt>Enum type & field names</dt>
|
|
|
|
|
<dd>
|
|
|
|
|
<p>
|
|
|
|
|
All enums should have a 'vir' prefix in their typedef name,
|
|
|
|
|
and each following word should have its first letter in
|
|
|
|
|
uppercase. The enum name should match the typedef name with
|
|
|
|
|
a leading underscore. The enum member names should be in all
|
|
|
|
|
uppercase, and use an underscore to separate each word. The
|
|
|
|
|
enum member name prefix should match the enum typedef name.
|
|
|
|
|
</p>
|
|
|
|
|
<pre>
|
|
|
|
|
typedef enum _virSocketType virSocketType;
|
|
|
|
|
enum _virSocketType {
|
|
|
|
|
VIR_SOCKET_TYPE_IPV4,
|
|
|
|
|
VIR_SOCKET_TYPE_IPV6,
|
|
|
|
|
};</pre>
|
|
|
|
|
</dd>
|
|
|
|
|
<dt>Struct type names</dt>
|
|
|
|
|
<dd>
|
|
|
|
|
<p>
|
|
|
|
|
All structs should have a 'vir' prefix in their typedef name,
|
|
|
|
|
and each following word should have its first letter in
|
|
|
|
|
uppercase. The struct name should be the same as the typedef
|
|
|
|
|
name with a leading underscore. A second typedef should be
|
|
|
|
|
given for a pointer to the struct with a 'Ptr' suffix.
|
|
|
|
|
</p>
|
|
|
|
|
<pre>
|
|
|
|
|
typedef struct _virHashTable virHashTable;
|
|
|
|
|
typedef virHashTable *virHashTablePtr;
|
|
|
|
|
struct _virHashTable {
|
|
|
|
|
...
|
|
|
|
|
};</pre>
|
|
|
|
|
</dd>
|
|
|
|
|
<dt>Function names</dt>
|
|
|
|
|
<dd>
|
|
|
|
|
<p>
|
|
|
|
|
All functions should have a 'vir' prefix in their name,
|
|
|
|
|
followed by one or more words with first letter of each
|
|
|
|
|
word capitalized. Underscores should not be used in function
|
|
|
|
|
names. If the function is operating on an object, then the
|
|
|
|
|
function name prefix should match the object typedef name,
|
|
|
|
|
otherwise it should match the filename. Following this
|
|
|
|
|
comes the verb / action name, and finally an optional
|
|
|
|
|
subject name. For example, given an object 'virHashTable',
|
|
|
|
|
all functions should have a name 'virHashTable$VERB' or
|
|
|
|
|
'virHashTable$VERB$SUBJECT", e.g. 'virHashTableLookup'
|
|
|
|
|
or 'virHashTableGetValue'.
|
|
|
|
|
</p>
|
|
|
|
|
</dd>
|
|
|
|
|
<dt>Macro names</dt>
|
|
|
|
|
<dd>
|
|
|
|
|
<p>
|
|
|
|
|
All macros should have a "VIR" prefix in their name, followed
|
|
|
|
|
by one or more uppercase words separated by underscores. The
|
|
|
|
|
macro argument names should be in lowercase. Aside from having
|
|
|
|
|
a "VIR" prefix there are no common practices for the rest of
|
|
|
|
|
the macro name.
|
|
|
|
|
</p>
|
|
|
|
|
</dd>
|
|
|
|
|
</dl>
|
2009-06-29 11:09:17 +00:00
|
|
|
|
|
|
|
|
<h2><a name="indent">Code indentation</a></h2>
|
|
|
|
|
<p>
|
|
|
|
|
Libvirt's C source code generally adheres to some basic code-formatting
|
|
|
|
|
conventions. The existing code base is not totally consistent on this
|
|
|
|
|
front, but we do prefer that contributed code be formatted similarly.
|
|
|
|
|
In short, use spaces-not-TABs for indentation, use 4 spaces for each
|
|
|
|
|
indentation level, and other than that, follow the K&R style.
|
|
|
|
|
</p>
|
|
|
|
|
|
2011-03-17 02:35:17 +00:00
|
|
|
<p>
|
2014-03-21 12:07:03 +00:00
|
|
|
If you use Emacs, the project includes a file .dir-locals.el
|
|
|
|
|
that sets up the preferred indentation. If you use vim,
|
|
|
|
|
append the following to your ~/.vimrc file:
|
2011-03-17 02:35:17 +00:00
|
|
|
</p>
|
|
|
|
|
<pre>
|
|
|
|
|
set nocompatible
|
|
|
|
|
filetype on
|
|
|
|
|
set autoindent
|
|
|
|
|
set smartindent
|
|
|
|
|
set cindent
|
|
|
|
|
set tabstop=8
|
|
|
|
|
set shiftwidth=4
|
|
|
|
|
set expandtab
|
2014-03-21 12:07:03 +00:00
|
|
|
set cinoptions=(0,:0,l1,t0,L3
|
2011-03-17 02:35:17 +00:00
|
|
|
filetype plugin indent on
|
|
|
|
|
au FileType make setlocal noexpandtab
|
|
|
|
|
au BufRead,BufNewFile *.am setlocal noexpandtab
|
|
|
|
|
match ErrorMsg /\s\+$\| \+\ze\t/
|
|
|
|
|
</pre>
|
|
|
|
|
<p>
|
|
|
|
|
Or if you don't want to mess your ~/.vimrc up, you can save the above
|
|
|
|
|
into a file called .lvimrc (not .vimrc) located at the root of libvirt
|
|
|
|
|
source, then install a vim script from
|
|
|
|
|
http://www.vim.org/scripts/script.php?script_id=1408,
|
|
|
|
|
which will load the .lvimrc only when you edit libvirt code.
|
|
|
|
|
</p>
|
|
|
|
|
|
2009-06-29 11:09:17 +00:00
|
|
|
<h2><a name="formatting">Code formatting (especially for new code)</a></h2>
|
|
|
|
|
|
|
|
|
|
<p>
|
|
|
|
|
With new code, we can be even more strict.
|
|
|
|
|
Please apply the following function (using GNU indent) to any new code.
|
|
|
|
|
Note that this also gives you an idea of the type of spacing we prefer
|
|
|
|
|
around operators and keywords:
|
|
|
|
|
</p>
|
|
|
|
|
|
2010-11-12 14:33:00 +00:00
|
|
|
<pre>
|
2009-06-29 11:09:17 +00:00
|
|
|
indent-libvirt()
|
|
|
|
|
{
|
|
|
|
|
indent -bad -bap -bbb -bli4 -br -ce -brs -cs -i4 -l75 -lc75 \
|
|
|
|
|
-sbi4 -psl -saf -sai -saw -sbi4 -ss -sc -cdw -cli4 -npcs -nbc \
|
|
|
|
|
--no-tabs "$@"
|
|
|
|
|
}
|
|
|
|
|
</pre>
|
|
|
|
|
|
|
|
|
|
<p>
|
2010-03-09 16:59:25 +00:00
|
|
|
Note that sometimes you'll have to post-process that output further, by
|
2010-11-12 14:33:00 +00:00
|
|
|
piping it through <code>expand -i</code>, since some leading TABs can get through.
|
2009-06-29 11:09:17 +00:00
|
|
|
Usually they're in macro definitions or strings, and should be converted
|
|
|
|
|
anyhow.
|
|
|
|
|
</p>
|
|
|
|
|
|
2011-03-30 15:48:51 +00:00
|
|
|
<p>
|
|
|
|
|
Libvirt requires a C99 compiler for various reasons. However,
|
|
|
|
|
most of the code base prefers to stick to C89 syntax unless
|
|
|
|
|
there is a compelling reason otherwise. For example, it is
|
|
|
|
|
preferable to use <code>/* */</code> comments rather
|
|
|
|
|
than <code>//</code>. Also, when declaring local variables, the
|
|
|
|
|
prevailing style has been to declare them at the beginning of a
|
|
|
|
|
scope, rather than immediately before use.
|
|
|
|
|
</p>
|
|
|
|
|
|
2009-06-29 11:09:17 +00:00
|
|
|
|
2012-10-17 09:25:35 +00:00
|
|
|
<h2><a name="bracket_spacing">Bracket spacing</a></h2>
|
|
|
|
|
|
|
|
|
|
<p>
|
|
|
|
|
The keywords <code>if</code>, <code>for</code>, <code>while</code>,
|
|
|
|
|
and <code>switch</code> must have a single space following them
|
2013-01-30 10:01:31 +00:00
|
|
|
before the opening bracket. E.g.
|
2012-10-17 09:25:35 +00:00
|
|
|
</p>
|
|
|
|
|
<pre>
|
|
|
|
|
if(foo) // Bad
|
|
|
|
|
if (foo) // Good
|
|
|
|
|
</pre>
|
|
|
|
|
|
|
|
|
|
<p>
|
|
|
|
|
Function implementations must <strong>not</strong> have any whitespace
|
2013-01-30 10:01:31 +00:00
|
|
|
between the function name and the opening bracket. E.g.
|
2012-10-17 09:25:35 +00:00
|
|
|
</p>
|
|
|
|
|
<pre>
|
|
|
|
|
int foo (int wizz) // Bad
|
|
|
|
|
int foo(int wizz) // Good
|
|
|
|
|
</pre>
|
|
|
|
|
|
|
|
|
|
<p>
|
|
|
|
|
Function calls must <strong>not</strong> have any whitespace
|
2013-01-30 10:01:31 +00:00
|
|
|
between the function name and the opening bracket. E.g.
|
2012-10-17 09:25:35 +00:00
|
|
|
</p>
|
|
|
|
|
<pre>
|
|
|
|
|
bar = foo (wizz); // Bad
|
|
|
|
|
bar = foo(wizz); // Good
|
|
|
|
|
</pre>
|
|
|
|
|
|
|
|
|
|
<p>
|
|
|
|
|
Function typedefs must <strong>not</strong> have any whitespace
|
|
|
|
|
between the closing bracket of the function name and opening
|
2013-01-30 10:01:31 +00:00
|
|
|
bracket of the arg list. E.g.
|
2012-10-17 09:25:35 +00:00
|
|
|
</p>
|
|
|
|
|
<pre>
|
|
|
|
|
typedef int (*foo) (int wizz); // Bad
|
|
|
|
|
typedef int (*foo)(int wizz); // Good
|
|
|
|
|
</pre>
|
|
|
|
|
|
|
|
|
|
<p>
|
|
|
|
|
There must not be any whitespace immediately following any
|
2013-01-30 10:01:31 +00:00
|
|
|
opening bracket, or immediately prior to any closing bracket. E.g.
|
2012-10-17 09:25:35 +00:00
|
|
|
</p>
|
|
|
|
|
<pre>
|
|
|
|
|
int foo( int wizz ); // Bad
|
|
|
|
|
int foo(int wizz); // Good
|
|
|
|
|
</pre>
|
|
|
|
|
|
2013-11-19 21:29:44 +00:00
|
|
|
<h2><a name="comma">Commas</a></h2>
|
|
|
|
|
|
|
|
|
|
<p>
|
|
|
|
|
Commas should always be followed by a space or end of line, and
|
|
|
|
|
never have leading space; this is enforced during 'make
|
|
|
|
|
syntax-check'.
|
|
|
|
|
</p>
|
|
|
|
|
<pre>
|
|
|
|
|
call(a,b ,c);// Bad
|
|
|
|
|
call(a, b, c); // Good
|
|
|
|
|
</pre>
|
|
|
|
|
|
|
|
|
|
<p>
|
|
|
|
|
When declaring an enum or using a struct initializer that
|
|
|
|
|
occupies more than one line, use a trailing comma. That way,
|
|
|
|
|
future edits to extend the list only have to add a line, rather
|
|
|
|
|
than modify an existing line to add the intermediate comma. Any
|
|
|
|
|
sentinel enumerator value with a name ending in _LAST is exempt,
|
|
|
|
|
since you would extend such an enum before the _LAST element.
|
|
|
|
|
Another reason to favor trailing commas is that it requires less
|
|
|
|
|
effort to produce via code generators. Note that the syntax
|
|
|
|
|
checker is unable to enforce a style of trailing commas, so
|
|
|
|
|
there are counterexamples in existing code which do not use it;
|
|
|
|
|
also, while C99 allows trailing commas, remember that JSON and
|
|
|
|
|
XDR do not.
|
|
|
|
|
</p>
|
|
|
|
|
<pre>
|
|
|
|
|
enum {
|
|
|
|
|
VALUE_ONE,
|
|
|
|
|
VALUE_TWO // Bad
|
|
|
|
|
};
|
|
|
|
|
enum {
|
|
|
|
|
VALUE_THREE,
|
|
|
|
|
VALUE_FOUR, // Good
|
|
|
|
|
};
|
|
|
|
|
</pre>
|
|
|
|
|
|
2013-05-24 16:43:45 +00:00
|
|
|
<h2><a name="semicolon">Semicolons</a></h2>
|
|
|
|
|
|
|
|
|
|
<p>
|
|
|
|
|
Semicolons should never have a space beforehand. Inside the
|
|
|
|
|
condition of a <code>for</code> loop, there should always be a
|
|
|
|
|
space or line break after each semicolon, except for the special
|
|
|
|
|
case of an infinite loop (although more infinite loops
|
|
|
|
|
use <code>while</code>). While not enforced, loop counters
|
|
|
|
|
generally use post-increment.
|
|
|
|
|
</p>
|
|
|
|
|
<pre>
|
|
|
|
|
for (i = 0 ;i < limit ; ++i) { // Bad
|
|
|
|
|
for (i = 0; i < limit; i++) { // Good
|
|
|
|
|
for (;;) { // ok
|
|
|
|
|
while (1) { // Better
|
|
|
|
|
</pre>
|
|
|
|
|
<p>
|
|
|
|
|
Empty loop bodies are better represented with curly braces and a
|
|
|
|
|
comment, although use of a semicolon is not currently rejected.
|
|
|
|
|
</p>
|
|
|
|
|
<pre>
|
|
|
|
|
while ((rc = waitpid(pid, &st, 0) == -1) &&
|
|
|
|
|
errno == EINTR); // ok
|
|
|
|
|
while ((rc = waitpid(pid, &st, 0) == -1) &&
|
|
|
|
|
errno == EINTR) { // Better
|
|
|
|
|
/* nothing */
|
|
|
|
|
}
|
|
|
|
|
</pre>
|
|
|
|
|
|
2010-04-15 17:31:04 +00:00
|
|
|
<h2><a name="curly_braces">Curly braces</a></h2>
|
|
|
|
|
|
|
|
|
|
<p>
|
2010-11-12 14:33:00 +00:00
|
|
|
Omit the curly braces around an <code>if</code>, <code>while</code>,
|
2014-11-13 13:56:53 +00:00
|
|
|
<code>for</code> etc. body only when both that body and the condition
|
|
|
|
|
itself occupy a single line. In every other case we require
|
2010-04-15 17:31:04 +00:00
|
|
|
the braces. This ensures that it is trivially easy to identify a
|
2010-11-12 14:33:00 +00:00
|
|
|
single-<i>statement</i> loop: each has only one <i>line</i> in its body.
|
2010-04-15 17:31:04 +00:00
|
|
|
</p>
|
|
|
|
|
|
2010-11-12 14:33:00 +00:00
|
|
|
<pre>
|
2014-11-13 13:56:53 +00:00
|
|
|
while (expr) // single line body; {} is forbidden
|
|
|
|
|
single_line_stmt();
|
|
|
|
|
</pre>
|
|
|
|
|
|
|
|
|
|
<pre>
|
|
|
|
|
while (expr(arg1,
|
|
|
|
|
arg2)) // indentation makes it obvious it is single line,
|
|
|
|
|
single_line_stmt(); // {} is optional (not enforced either way)
|
|
|
|
|
</pre>
|
|
|
|
|
|
|
|
|
|
<pre>
|
|
|
|
|
while (expr1 &&
|
2014-12-10 07:25:08 +00:00
|
|
|
expr2) { // multi-line, at same indentation, {} required
|
2010-11-12 14:33:00 +00:00
|
|
|
single_line_stmt();
|
2014-12-10 07:25:08 +00:00
|
|
|
}
|
2010-11-12 14:33:00 +00:00
|
|
|
</pre>
|
2010-04-15 17:31:04 +00:00
|
|
|
|
|
|
|
|
<p>
|
2013-04-19 20:18:14 +00:00
|
|
|
However, the moment your loop/if/else body extends on to a second
|
2010-04-15 17:31:04 +00:00
|
|
|
line, for whatever reason (even if it's just an added comment), then
|
|
|
|
|
you should add braces. Otherwise, it would be too easy to insert a
|
|
|
|
|
statement just before that comment (without adding braces), thinking
|
|
|
|
|
it is already a multi-statement loop:
|
|
|
|
|
</p>
|
|
|
|
|
|
2010-11-12 14:33:00 +00:00
|
|
|
<pre>
|
2010-04-15 17:31:04 +00:00
|
|
|
while (true) // BAD! multi-line body with no braces
|
|
|
|
|
/* comment... */
|
2010-11-12 14:33:00 +00:00
|
|
|
single_line_stmt();
|
|
|
|
|
</pre>
|
2010-04-15 17:31:04 +00:00
|
|
|
<p>
|
|
|
|
|
Do this instead:
|
|
|
|
|
</p>
|
2010-11-12 14:33:00 +00:00
|
|
|
<pre>
|
2010-04-15 17:31:04 +00:00
|
|
|
while (true) { // Always put braces around a multi-line body.
|
|
|
|
|
/* comment... */
|
2010-11-12 14:33:00 +00:00
|
|
|
single_line_stmt();
|
|
|
|
|
}
|
|
|
|
|
</pre>
|
2010-04-15 17:31:04 +00:00
|
|
|
<p>
|
|
|
|
|
There is one exception: when the second body line is not at the same
|
|
|
|
|
indentation level as the first body line:
|
|
|
|
|
</p>
|
2010-11-12 14:33:00 +00:00
|
|
|
<pre>
|
2010-04-15 17:31:04 +00:00
|
|
|
if (expr)
|
2010-11-12 14:33:00 +00:00
|
|
|
die("a diagnostic that would make this line"
|
|
|
|
|
" extend past the 80-column limit"));
|
|
|
|
|
</pre>
|
2010-04-15 17:31:04 +00:00
|
|
|
|
|
|
|
|
<p>
|
|
|
|
|
It is safe to omit the braces in the code above, since the
|
|
|
|
|
further-indented second body line makes it obvious that this is still
|
|
|
|
|
a single-statement body.
|
|
|
|
|
</p>
|
|
|
|
|
|
|
|
|
|
<p>
|
|
|
|
|
To reiterate, don't do this:
|
|
|
|
|
</p>
|
|
|
|
|
|
2010-11-12 14:33:00 +00:00
|
|
|
<pre>
|
2010-04-15 17:31:04 +00:00
|
|
|
if (expr) // BAD: no braces around...
|
|
|
|
|
while (expr_2) { // ... a multi-line body
|
|
|
|
|
...
|
2010-11-12 14:33:00 +00:00
|
|
|
}
|
|
|
|
|
</pre>
|
2010-04-15 17:31:04 +00:00
|
|
|
|
|
|
|
|
<p>
|
|
|
|
|
Do this, instead:
|
|
|
|
|
</p>
|
|
|
|
|
|
2010-11-12 14:33:00 +00:00
|
|
|
<pre>
|
2010-04-15 17:31:04 +00:00
|
|
|
if (expr) {
|
|
|
|
|
while (expr_2) {
|
|
|
|
|
...
|
|
|
|
|
}
|
2010-11-12 14:33:00 +00:00
|
|
|
}
|
|
|
|
|
</pre>
|
2010-04-15 17:31:04 +00:00
|
|
|
|
|
|
|
|
<p>
|
|
|
|
|
However, there is one exception in the other direction, when even a
|
|
|
|
|
one-line block should have braces. That occurs when that one-line,
|
2011-01-05 17:58:35 +00:00
|
|
|
brace-less block is an <code>if</code> or <code>else</code>
|
|
|
|
|
block, and the counterpart block <b>does</b> use braces. In
|
|
|
|
|
that case, put braces around both blocks. Also, if
|
|
|
|
|
the <code>else</code> block is much shorter than
|
|
|
|
|
the <code>if</code> block, consider negating the
|
|
|
|
|
<code>if</code>-condition and swapping the bodies, putting the
|
|
|
|
|
short block first and making the longer, multi-line block be the
|
2010-11-12 14:33:00 +00:00
|
|
|
<code>else</code> block.
|
2010-04-15 17:31:04 +00:00
|
|
|
</p>
|
|
|
|
|
|
2010-11-12 14:33:00 +00:00
|
|
|
<pre>
|
2010-04-15 17:31:04 +00:00
|
|
|
if (expr) {
|
|
|
|
|
...
|
|
|
|
|
...
|
|
|
|
|
}
|
|
|
|
|
else
|
2011-01-05 17:58:35 +00:00
|
|
|
x = y; // BAD: braceless "else" with braced "then",
|
|
|
|
|
// and short block last
|
|
|
|
|
|
|
|
|
|
if (expr)
|
|
|
|
|
x = y; // BAD: braceless "if" with braced "else"
|
|
|
|
|
else {
|
|
|
|
|
...
|
|
|
|
|
...
|
|
|
|
|
}
|
2010-11-12 14:33:00 +00:00
|
|
|
</pre>
|
2010-04-15 17:31:04 +00:00
|
|
|
|
|
|
|
|
<p>
|
2011-01-05 17:58:35 +00:00
|
|
|
Keeping braces consistent and putting the short block first is
|
|
|
|
|
preferred, especially when the multi-line body is more than a
|
2010-04-15 17:31:04 +00:00
|
|
|
few lines long, because it is easier to read and grasp the semantics of
|
|
|
|
|
an if-then-else block when the simpler block occurs first, rather than
|
|
|
|
|
after the more involved block:
|
|
|
|
|
</p>
|
|
|
|
|
|
2010-11-12 14:33:00 +00:00
|
|
|
<pre>
|
2011-01-05 17:58:35 +00:00
|
|
|
if (!expr) {
|
2010-04-15 17:31:04 +00:00
|
|
|
x = y; // putting the smaller block first is more readable
|
2011-01-05 17:58:35 +00:00
|
|
|
} else {
|
2010-04-15 17:31:04 +00:00
|
|
|
...
|
|
|
|
|
...
|
2010-11-12 14:33:00 +00:00
|
|
|
}
|
|
|
|
|
</pre>
|
2010-04-15 17:31:04 +00:00
|
|
|
|
|
|
|
|
<p>
|
2011-01-05 17:58:35 +00:00
|
|
|
But if negating a complex condition is too ugly, then at least
|
|
|
|
|
add braces:
|
2010-04-15 17:31:04 +00:00
|
|
|
</p>
|
|
|
|
|
|
2010-11-12 14:33:00 +00:00
|
|
|
<pre>
|
2011-01-05 17:58:35 +00:00
|
|
|
if (complex expr not worth negating) {
|
2010-04-15 17:31:04 +00:00
|
|
|
...
|
|
|
|
|
...
|
|
|
|
|
} else {
|
|
|
|
|
x = y;
|
2010-11-12 14:33:00 +00:00
|
|
|
}
|
|
|
|
|
</pre>
|
2010-04-15 17:31:04 +00:00
|
|
|
|
2014-09-03 22:18:19 +00:00
|
|
|
<p>Use hanging braces for compound statements: the opening brace
|
|
|
|
|
of a compound statement should be on the same line as the
|
|
|
|
|
condition being tested. Only top-level function bodies, nested
|
|
|
|
|
scopes, and compound structure declarations should ever have {
|
|
|
|
|
on a line by itself.
|
|
|
|
|
</p>
|
|
|
|
|
|
|
|
|
|
<pre>
|
|
|
|
|
void
|
|
|
|
|
foo(int a, int b)
|
|
|
|
|
{ // correct - function body
|
|
|
|
|
int 2d[][] = {
|
|
|
|
|
{ // correct - complex initialization
|
|
|
|
|
1, 2,
|
|
|
|
|
},
|
|
|
|
|
};
|
|
|
|
|
if (a)
|
|
|
|
|
{ // BAD: compound brace on its own line
|
|
|
|
|
do_stuff();
|
|
|
|
|
}
|
|
|
|
|
{ // correct - nested scope
|
|
|
|
|
int tmp;
|
|
|
|
|
if (a < b) { // correct - hanging brace
|
|
|
|
|
tmp = b;
|
|
|
|
|
b = a;
|
|
|
|
|
a = tmp;
|
|
|
|
|
}
|
|
|
|
|
}
|
|
|
|
|
}
|
|
|
|
|
</pre>
|
|
|
|
|
|
2012-09-11 12:01:56 +00:00
|
|
|
<h2><a name="preprocessor">Preprocessor</a></h2>
|
2010-03-09 00:02:45 +00:00
|
|
|
|
alloc: make VIR_APPEND_ELEMENT safer
VIR_APPEND_ELEMENT(array, size, elem) was not safe if the expression
for 'size' had side effects. While no one in the current code base
was trying to pass side effects, we might as well be robust and
explicitly document our intentions.
* src/util/viralloc.c (virInsertElementsN): Add special case.
* src/util/viralloc.h (VIR_APPEND_ELEMENT): Use it.
(VIR_ALLOC, VIR_ALLOC_N, VIR_REALLOC_N, VIR_EXPAND_N)
(VIR_RESIZE_N, VIR_SHRINK_N, VIR_INSERT_ELEMENT)
(VIR_DELETE_ELEMENT, VIR_ALLOC_VAR, VIR_FREE): Document
which macros are safe in the presence of side effects.
* docs/hacking.html.in: Document this.
* HACKING: Regenerate.
Signed-off-by: Eric Blake <eblake@redhat.com>
2013-05-06 22:21:15 +00:00
|
|
|
<p>Macros defined with an ALL_CAPS name should generally be
|
|
|
|
|
assumed to be unsafe with regards to arguments with side-effects
|
|
|
|
|
(that is, MAX(a++, b--) might increment a or decrement b too
|
|
|
|
|
many or too few times). Exceptions to this rule are explicitly
|
2013-05-07 02:42:44 +00:00
|
|
|
documented for macros in viralloc.h and virstring.h.
|
alloc: make VIR_APPEND_ELEMENT safer
VIR_APPEND_ELEMENT(array, size, elem) was not safe if the expression
for 'size' had side effects. While no one in the current code base
was trying to pass side effects, we might as well be robust and
explicitly document our intentions.
* src/util/viralloc.c (virInsertElementsN): Add special case.
* src/util/viralloc.h (VIR_APPEND_ELEMENT): Use it.
(VIR_ALLOC, VIR_ALLOC_N, VIR_REALLOC_N, VIR_EXPAND_N)
(VIR_RESIZE_N, VIR_SHRINK_N, VIR_INSERT_ELEMENT)
(VIR_DELETE_ELEMENT, VIR_ALLOC_VAR, VIR_FREE): Document
which macros are safe in the presence of side effects.
* docs/hacking.html.in: Document this.
* HACKING: Regenerate.
Signed-off-by: Eric Blake <eblake@redhat.com>
2013-05-06 22:21:15 +00:00
|
|
|
</p>
|
|
|
|
|
|
2010-03-09 00:02:45 +00:00
|
|
|
<p>
|
|
|
|
|
For variadic macros, stick with C99 syntax:
|
2010-03-13 14:04:34 +00:00
|
|
|
</p>
|
2010-11-12 14:33:00 +00:00
|
|
|
<pre>
|
2010-03-09 00:02:45 +00:00
|
|
|
#define vshPrint(_ctl, ...) fprintf(stdout, __VA_ARGS__)
|
2010-11-12 14:33:00 +00:00
|
|
|
</pre>
|
2010-03-09 00:02:45 +00:00
|
|
|
|
|
|
|
|
<p>Use parenthesis when checking if a macro is defined, and use
|
|
|
|
|
indentation to track nesting:
|
2010-03-13 14:04:34 +00:00
|
|
|
</p>
|
2010-11-12 14:33:00 +00:00
|
|
|
<pre>
|
2010-03-09 00:02:45 +00:00
|
|
|
#if defined(HAVE_POSIX_FALLOCATE) && !defined(HAVE_FALLOCATE)
|
2014-08-22 12:59:28 +00:00
|
|
|
# define fallocate(a, ignored, b, c) posix_fallocate(a, b, c)
|
2010-03-09 00:02:45 +00:00
|
|
|
#endif
|
2010-11-12 14:33:00 +00:00
|
|
|
</pre>
|
2010-03-09 00:02:45 +00:00
|
|
|
|
2012-09-11 12:01:56 +00:00
|
|
|
<h2><a name="types">C types</a></h2>
|
2009-06-29 11:09:17 +00:00
|
|
|
|
|
|
|
|
<p>
|
|
|
|
|
Use the right type.
|
|
|
|
|
</p>
|
|
|
|
|
|
|
|
|
|
<h3>Scalars</h3>
|
|
|
|
|
|
|
|
|
|
<ul>
|
2010-11-12 14:33:00 +00:00
|
|
|
<li>If you're using <code>int</code> or <code>long</code>, odds are
|
|
|
|
|
good that there's a better type.</li>
|
2009-06-29 11:09:17 +00:00
|
|
|
<li>If a variable is counting something, be sure to declare it with an
|
2009-11-06 15:04:19 +00:00
|
|
|
unsigned type.</li>
|
2010-11-12 14:33:00 +00:00
|
|
|
<li>If it's memory-size-related, use <code>size_t</code> (use
|
|
|
|
|
<code>ssize_t</code> only if required).</li>
|
|
|
|
|
<li>If it's file-size related, use uintmax_t, or maybe <code>off_t</code>.</li>
|
|
|
|
|
<li>If it's file-offset related (i.e., signed), use <code>off_t</code>.</li>
|
|
|
|
|
<li>If it's just counting small numbers use <code>unsigned int</code>;
|
2009-11-06 15:04:19 +00:00
|
|
|
(on all but oddball embedded systems, you can assume that that
|
|
|
|
|
type is at least four bytes wide).</li>
|
2010-11-12 14:33:00 +00:00
|
|
|
<li>If a variable has boolean semantics, give it the <code>bool</code> type
|
|
|
|
|
and use the corresponding <code>true</code> and <code>false</code> macros.
|
|
|
|
|
It's ok to include <stdbool.h>, since libvirt's use of gnulib ensures
|
2009-11-06 15:04:19 +00:00
|
|
|
that it exists and is usable.</li>
|
2009-06-29 11:09:17 +00:00
|
|
|
<li>In the unusual event that you require a specific width, use a
|
2010-11-12 14:33:00 +00:00
|
|
|
standard type like <code>int32_t</code>, <code>uint32_t</code>,
|
|
|
|
|
<code>uint64_t</code>, etc.</li>
|
|
|
|
|
<li>While using <code>bool</code> is good for readability, it comes with
|
|
|
|
|
minor caveats:
|
2009-11-06 15:04:19 +00:00
|
|
|
<ul>
|
2010-11-12 14:33:00 +00:00
|
|
|
<li>Don't use <code>bool</code> in places where the type size must be constant across
|
2009-11-06 15:04:19 +00:00
|
|
|
all systems, like public interfaces and on-the-wire protocols. Note
|
2010-11-12 14:33:00 +00:00
|
|
|
that it would be possible (albeit wasteful) to use <code>bool</code> in libvirt's
|
|
|
|
|
logical wire protocol, since XDR maps that to its lower-level <code>bool_t</code>
|
|
|
|
|
type, which <b>is</b> fixed-size.</li>
|
|
|
|
|
<li>Don't compare a bool variable against the literal, <code>true</code>,
|
|
|
|
|
since a value with a logical non-false value need not be <code>1</code>.
|
|
|
|
|
I.e., don't write <code>if (seen == true) ...</code>. Rather,
|
|
|
|
|
write <code>if (seen)...</code>.</li>
|
2009-11-06 15:04:19 +00:00
|
|
|
</ul>
|
2009-06-29 11:09:17 +00:00
|
|
|
</li>
|
|
|
|
|
</ul>
|
|
|
|
|
|
|
|
|
|
<p>
|
|
|
|
|
Of course, take all of the above with a grain of salt. If you're about
|
2010-11-12 14:33:00 +00:00
|
|
|
to use some system interface that requires a type like <code>size_t</code>,
|
|
|
|
|
<code>pid_t</code> or <code>off_t</code>, use matching types for any
|
|
|
|
|
corresponding variables.
|
2009-06-29 11:09:17 +00:00
|
|
|
</p>
|
|
|
|
|
|
|
|
|
|
<p>
|
2010-11-12 14:33:00 +00:00
|
|
|
Also, if you try to use e.g., <code>unsigned int</code> as a type, and that
|
2009-06-29 11:09:17 +00:00
|
|
|
conflicts with the signedness of a related variable, sometimes
|
2010-11-12 14:33:00 +00:00
|
|
|
it's best just to use the <b>wrong</b> type, if <i>pulling the thread</i>
|
2009-06-29 11:09:17 +00:00
|
|
|
and fixing all related variables would be too invasive.
|
|
|
|
|
</p>
|
|
|
|
|
|
|
|
|
|
<p>
|
|
|
|
|
Finally, while using descriptive types is important, be careful not to
|
|
|
|
|
go overboard. If whatever you're doing causes warnings, or requires
|
|
|
|
|
casts, then reconsider or ask for help.
|
|
|
|
|
</p>
|
|
|
|
|
|
|
|
|
|
<h3>Pointers</h3>
|
|
|
|
|
|
|
|
|
|
<p>
|
2010-11-12 14:33:00 +00:00
|
|
|
Ensure that all of your pointers are <i>const-correct</i>.
|
2009-06-29 11:09:17 +00:00
|
|
|
Unless a pointer is used to modify the pointed-to storage,
|
2010-11-12 14:33:00 +00:00
|
|
|
give it the <code>const</code> attribute. That way, the reader knows
|
2009-06-29 11:09:17 +00:00
|
|
|
up-front that this is a read-only pointer. Perhaps more
|
|
|
|
|
importantly, if we're diligent about this, when you see a non-const
|
|
|
|
|
pointer, you're guaranteed that it is used to modify the storage
|
|
|
|
|
it points to, or it is aliased to another pointer that is.
|
|
|
|
|
</p>
|
|
|
|
|
|
|
|
|
|
<h2><a name="memalloc">Low level memory management</a></h2>
|
|
|
|
|
|
|
|
|
|
<p>
|
|
|
|
|
Use of the malloc/free/realloc/calloc APIs is deprecated in the libvirt
|
|
|
|
|
codebase, because they encourage a number of serious coding bugs and do
|
|
|
|
|
not enable compile time verification of checks for NULL. Instead of these
|
alloc: make VIR_APPEND_ELEMENT safer
VIR_APPEND_ELEMENT(array, size, elem) was not safe if the expression
for 'size' had side effects. While no one in the current code base
was trying to pass side effects, we might as well be robust and
explicitly document our intentions.
* src/util/viralloc.c (virInsertElementsN): Add special case.
* src/util/viralloc.h (VIR_APPEND_ELEMENT): Use it.
(VIR_ALLOC, VIR_ALLOC_N, VIR_REALLOC_N, VIR_EXPAND_N)
(VIR_RESIZE_N, VIR_SHRINK_N, VIR_INSERT_ELEMENT)
(VIR_DELETE_ELEMENT, VIR_ALLOC_VAR, VIR_FREE): Document
which macros are safe in the presence of side effects.
* docs/hacking.html.in: Document this.
* HACKING: Regenerate.
Signed-off-by: Eric Blake <eblake@redhat.com>
2013-05-06 22:21:15 +00:00
|
|
|
routines, use the macros from viralloc.h.
|
2009-06-29 11:09:17 +00:00
|
|
|
</p>
|
|
|
|
|
|
|
|
|
|
<ul>
|
2010-08-13 21:00:47 +00:00
|
|
|
<li><p>To allocate a single object:</p>
|
|
|
|
|
|
2009-06-29 11:09:17 +00:00
|
|
|
<pre>
|
2010-11-12 14:33:00 +00:00
|
|
|
virDomainPtr domain;
|
2009-06-29 11:09:17 +00:00
|
|
|
|
2013-07-04 10:21:16 +00:00
|
|
|
if (VIR_ALLOC(domain) < 0)
|
2010-11-12 14:33:00 +00:00
|
|
|
return NULL;
|
|
|
|
|
</pre>
|
|
|
|
|
</li>
|
2009-06-29 11:09:17 +00:00
|
|
|
|
2010-08-13 21:00:47 +00:00
|
|
|
<li><p>To allocate an array of objects:</p>
|
2009-06-29 11:09:17 +00:00
|
|
|
<pre>
|
2010-11-12 14:33:00 +00:00
|
|
|
virDomainPtr domains;
|
2010-08-13 21:00:47 +00:00
|
|
|
size_t ndomains = 10;
|
2009-06-29 11:09:17 +00:00
|
|
|
|
2013-07-04 10:21:16 +00:00
|
|
|
if (VIR_ALLOC_N(domains, ndomains) < 0)
|
2010-11-12 14:33:00 +00:00
|
|
|
return NULL;
|
|
|
|
|
</pre>
|
|
|
|
|
</li>
|
2009-06-29 11:09:17 +00:00
|
|
|
|
2010-08-13 21:00:47 +00:00
|
|
|
<li><p>To allocate an array of object pointers:</p>
|
2009-06-29 11:09:17 +00:00
|
|
|
<pre>
|
2010-11-12 14:33:00 +00:00
|
|
|
virDomainPtr *domains;
|
2010-08-14 15:42:51 +00:00
|
|
|
size_t ndomains = 10;
|
2009-06-29 11:09:17 +00:00
|
|
|
|
2013-07-04 10:21:16 +00:00
|
|
|
if (VIR_ALLOC_N(domains, ndomains) < 0)
|
2010-11-12 14:33:00 +00:00
|
|
|
return NULL;
|
|
|
|
|
</pre>
|
|
|
|
|
</li>
|
2009-06-29 11:09:17 +00:00
|
|
|
|
2010-08-14 15:42:51 +00:00
|
|
|
<li><p>To re-allocate the array of domains to be 1 element
|
|
|
|
|
longer (however, note that repeatedly expanding an array by 1
|
|
|
|
|
scales quadratically, so this is recommended only for smaller
|
|
|
|
|
arrays):</p>
|
|
|
|
|
<pre>
|
|
|
|
|
virDomainPtr domains;
|
|
|
|
|
size_t ndomains = 0;
|
|
|
|
|
|
2013-07-04 10:21:16 +00:00
|
|
|
if (VIR_EXPAND_N(domains, ndomains, 1) < 0)
|
2010-08-14 15:42:51 +00:00
|
|
|
return NULL;
|
|
|
|
|
domains[ndomains - 1] = domain;
|
|
|
|
|
</pre></li>
|
|
|
|
|
|
|
|
|
|
<li><p>To ensure an array has room to hold at least one more
|
|
|
|
|
element (this approach scales better, but requires tracking
|
|
|
|
|
allocation separately from usage)</p>
|
|
|
|
|
|
2009-06-29 11:09:17 +00:00
|
|
|
<pre>
|
2010-08-14 15:42:51 +00:00
|
|
|
virDomainPtr domains;
|
|
|
|
|
size_t ndomains = 0;
|
|
|
|
|
size_t ndomains_max = 0;
|
|
|
|
|
|
2013-07-04 10:21:16 +00:00
|
|
|
if (VIR_RESIZE_N(domains, ndomains_max, ndomains, 1) < 0)
|
2010-11-12 14:33:00 +00:00
|
|
|
return NULL;
|
2010-08-14 15:42:51 +00:00
|
|
|
domains[ndomains++] = domain;
|
2010-11-12 14:33:00 +00:00
|
|
|
</pre>
|
|
|
|
|
</li>
|
2009-06-29 11:09:17 +00:00
|
|
|
|
2010-11-22 19:27:07 +00:00
|
|
|
<li><p>To trim an array of domains from its allocated size down
|
|
|
|
|
to the actual used size:</p>
|
2010-08-13 21:00:47 +00:00
|
|
|
|
|
|
|
|
<pre>
|
2010-08-14 15:42:51 +00:00
|
|
|
virDomainPtr domains;
|
|
|
|
|
size_t ndomains = x;
|
|
|
|
|
size_t ndomains_max = y;
|
|
|
|
|
|
2010-11-22 19:27:07 +00:00
|
|
|
VIR_SHRINK_N(domains, ndomains_max, ndomains_max - ndomains);
|
2010-08-13 21:00:47 +00:00
|
|
|
</pre></li>
|
|
|
|
|
|
2010-08-14 15:42:51 +00:00
|
|
|
<li><p>To free an array of domains:</p>
|
2009-06-29 11:09:17 +00:00
|
|
|
<pre>
|
2010-08-14 15:42:51 +00:00
|
|
|
virDomainPtr domains;
|
|
|
|
|
size_t ndomains = x;
|
|
|
|
|
size_t ndomains_max = y;
|
|
|
|
|
size_t i;
|
|
|
|
|
|
|
|
|
|
for (i = 0; i < ndomains; i++)
|
|
|
|
|
VIR_FREE(domains[i]);
|
|
|
|
|
VIR_FREE(domains);
|
|
|
|
|
ndomains_max = ndomains = 0;
|
2010-11-12 14:33:00 +00:00
|
|
|
</pre>
|
2010-08-14 15:42:51 +00:00
|
|
|
</li>
|
2009-06-29 11:09:17 +00:00
|
|
|
</ul>
|
|
|
|
|
|
2010-10-19 14:23:51 +00:00
|
|
|
<h2><a name="file_handling">File handling</a></h2>
|
2009-06-29 11:09:17 +00:00
|
|
|
|
2010-10-19 14:23:51 +00:00
|
|
|
<p>
|
2010-11-17 02:13:29 +00:00
|
|
|
Usage of the <code>fdopen()</code>, <code>close()</code>, <code>fclose()</code>
|
|
|
|
|
APIs is deprecated in libvirt code base to help avoiding double-closing of files
|
2012-10-11 16:31:20 +00:00
|
|
|
or file descriptors, which is particularly dangerous in a multi-threaded
|
|
|
|
|
application. Instead of these APIs, use the macros from virfile.h
|
2010-10-19 14:23:51 +00:00
|
|
|
</p>
|
|
|
|
|
|
2010-11-17 02:13:29 +00:00
|
|
|
<ul>
|
2010-08-13 21:00:47 +00:00
|
|
|
<li><p>Open a file from a file descriptor:</p>
|
2010-11-17 02:13:29 +00:00
|
|
|
|
|
|
|
|
<pre>
|
|
|
|
|
if ((file = VIR_FDOPEN(fd, "r")) == NULL) {
|
|
|
|
|
virReportSystemError(errno, "%s",
|
|
|
|
|
_("failed to open file from file descriptor"));
|
|
|
|
|
return -1;
|
|
|
|
|
}
|
|
|
|
|
/* fd is now invalid; only access the file using file variable */
|
|
|
|
|
</pre></li>
|
|
|
|
|
|
2010-08-13 21:00:47 +00:00
|
|
|
<li><p>Close a file descriptor:</p>
|
2010-10-19 14:23:51 +00:00
|
|
|
<pre>
|
2010-11-12 14:33:00 +00:00
|
|
|
if (VIR_CLOSE(fd) < 0) {
|
2010-11-17 02:13:29 +00:00
|
|
|
virReportSystemError(errno, "%s", _("failed to close file"));
|
2010-11-12 14:33:00 +00:00
|
|
|
}
|
2010-11-17 02:13:29 +00:00
|
|
|
</pre></li>
|
|
|
|
|
|
2010-08-13 21:00:47 +00:00
|
|
|
<li><p>Close a file:</p>
|
2010-11-17 02:13:29 +00:00
|
|
|
|
|
|
|
|
<pre>
|
|
|
|
|
if (VIR_FCLOSE(file) < 0) {
|
|
|
|
|
virReportSystemError(errno, "%s", _("failed to close file"));
|
|
|
|
|
}
|
|
|
|
|
</pre></li>
|
2010-10-19 14:23:51 +00:00
|
|
|
|
2010-08-13 21:00:47 +00:00
|
|
|
<li><p>Close a file or file descriptor in an error path, without losing
|
|
|
|
|
the previous <code>errno</code> value:</p>
|
2010-10-19 14:23:51 +00:00
|
|
|
|
|
|
|
|
<pre>
|
2010-11-12 14:33:00 +00:00
|
|
|
VIR_FORCE_CLOSE(fd);
|
2010-11-17 02:13:29 +00:00
|
|
|
VIR_FORCE_FCLOSE(file);
|
2010-11-12 14:33:00 +00:00
|
|
|
</pre>
|
|
|
|
|
</li>
|
2010-10-19 14:23:51 +00:00
|
|
|
</ul>
|
2009-06-29 11:09:17 +00:00
|
|
|
|
2010-03-08 15:26:30 +00:00
|
|
|
<h2><a name="string_comparision">String comparisons</a></h2>
|
2009-06-29 11:09:17 +00:00
|
|
|
|
|
|
|
|
<p>
|
|
|
|
|
Do not use the strcmp, strncmp, etc functions directly. Instead use
|
|
|
|
|
one of the following semantically named macros
|
|
|
|
|
</p>
|
|
|
|
|
|
|
|
|
|
<ul>
|
|
|
|
|
<li><p>For strict equality:</p>
|
2010-11-12 14:33:00 +00:00
|
|
|
<pre>
|
|
|
|
|
STREQ(a,b)
|
|
|
|
|
STRNEQ(a,b)
|
2009-06-29 11:09:17 +00:00
|
|
|
</pre>
|
|
|
|
|
</li>
|
|
|
|
|
|
2010-01-27 13:33:58 +00:00
|
|
|
<li><p>For case insensitive equality:</p>
|
2010-11-12 14:33:00 +00:00
|
|
|
<pre>
|
|
|
|
|
STRCASEEQ(a,b)
|
|
|
|
|
STRCASENEQ(a,b)
|
2009-06-29 11:09:17 +00:00
|
|
|
</pre>
|
|
|
|
|
</li>
|
|
|
|
|
|
|
|
|
|
<li><p>For strict equality of a substring:</p>
|
2010-11-12 14:33:00 +00:00
|
|
|
<pre>
|
|
|
|
|
STREQLEN(a,b,n)
|
|
|
|
|
STRNEQLEN(a,b,n)
|
2009-06-29 11:09:17 +00:00
|
|
|
</pre>
|
|
|
|
|
</li>
|
|
|
|
|
|
2010-01-27 13:33:58 +00:00
|
|
|
<li><p>For case insensitive equality of a substring:</p>
|
2010-11-12 14:33:00 +00:00
|
|
|
<pre>
|
|
|
|
|
STRCASEEQLEN(a,b,n)
|
|
|
|
|
STRCASENEQLEN(a,b,n)
|
2009-06-29 11:09:17 +00:00
|
|
|
</pre>
|
|
|
|
|
</li>
|
|
|
|
|
|
|
|
|
|
<li><p>For strict equality of a prefix:</p>
|
2010-11-12 14:33:00 +00:00
|
|
|
<pre>
|
|
|
|
|
STRPREFIX(a,b)
|
2011-10-06 11:32:49 +00:00
|
|
|
</pre>
|
|
|
|
|
</li>
|
|
|
|
|
<li><p>To avoid having to check if a or b are NULL:</p>
|
|
|
|
|
<pre>
|
|
|
|
|
STREQ_NULLABLE(a, b)
|
|
|
|
|
STRNEQ_NULLABLE(a, b)
|
2009-06-29 11:09:17 +00:00
|
|
|
</pre>
|
|
|
|
|
</li>
|
|
|
|
|
</ul>
|
|
|
|
|
|
|
|
|
|
|
2010-03-08 15:26:30 +00:00
|
|
|
<h2><a name="string_copying">String copying</a></h2>
|
|
|
|
|
|
|
|
|
|
<p>
|
|
|
|
|
Do not use the strncpy function. According to the man page, it
|
|
|
|
|
does <b>not</b> guarantee a NULL-terminated buffer, which makes
|
|
|
|
|
it extremely dangerous to use. Instead, use one of the
|
|
|
|
|
functionally equivalent functions:
|
|
|
|
|
</p>
|
2010-11-12 14:33:00 +00:00
|
|
|
|
|
|
|
|
<pre>
|
|
|
|
|
virStrncpy(char *dest, const char *src, size_t n, size_t destbytes)
|
|
|
|
|
</pre>
|
2010-03-08 15:26:30 +00:00
|
|
|
<p>
|
|
|
|
|
The first three arguments have the same meaning as for strncpy;
|
|
|
|
|
namely the destination, source, and number of bytes to copy,
|
|
|
|
|
respectively. The last argument is the number of bytes
|
|
|
|
|
available in the destination string; if a copy of the source
|
|
|
|
|
string (including a \0) will not fit into the destination, no
|
|
|
|
|
bytes are copied and the routine returns NULL. Otherwise, n
|
|
|
|
|
bytes from the source are copied into the destination and a
|
|
|
|
|
trailing \0 is appended.
|
|
|
|
|
</p>
|
|
|
|
|
|
2010-11-12 14:33:00 +00:00
|
|
|
<pre>
|
|
|
|
|
virStrcpy(char *dest, const char *src, size_t destbytes)
|
|
|
|
|
</pre>
|
2010-03-08 15:26:30 +00:00
|
|
|
<p>
|
|
|
|
|
Use this variant if you know you want to copy the entire src
|
|
|
|
|
string into dest. Note that this is a macro, so arguments could
|
|
|
|
|
be evaluated more than once. This is equivalent to
|
|
|
|
|
virStrncpy(dest, src, strlen(src), destbytes)
|
|
|
|
|
</p>
|
|
|
|
|
|
2010-11-12 14:33:00 +00:00
|
|
|
<pre>
|
|
|
|
|
virStrcpyStatic(char *dest, const char *src)
|
|
|
|
|
</pre>
|
2010-03-08 15:26:30 +00:00
|
|
|
<p>
|
|
|
|
|
Use this variant if you know you want to copy the entire src
|
2010-11-12 14:33:00 +00:00
|
|
|
string into dest <b>and</b> you know that your destination string is
|
2010-03-08 15:26:30 +00:00
|
|
|
a static string (i.e. that sizeof(dest) returns something
|
|
|
|
|
meaningful). Note that this is a macro, so arguments could be
|
|
|
|
|
evaluated more than once. This is equivalent to
|
|
|
|
|
virStrncpy(dest, src, strlen(src), sizeof(dest)).
|
|
|
|
|
</p>
|
|
|
|
|
|
2013-04-03 12:51:20 +00:00
|
|
|
<pre>
|
|
|
|
|
VIR_STRDUP(char *dst, const char *src);
|
|
|
|
|
VIR_STRNDUP(char *dst, const char *src, size_t n);
|
|
|
|
|
</pre>
|
|
|
|
|
<p>
|
|
|
|
|
You should avoid using strdup or strndup directly as they do not report
|
2013-05-07 02:42:44 +00:00
|
|
|
out-of-memory error, and do not allow a NULL source. Use
|
|
|
|
|
VIR_STRDUP or VIR_STRNDUP macros instead, which return 0 for
|
|
|
|
|
NULL source, 1 for successful copy, and -1 for allocation
|
|
|
|
|
failure with the error already reported. In very
|
2013-04-03 12:51:20 +00:00
|
|
|
specific cases, when you don't want to report the out-of-memory error, you
|
|
|
|
|
can use VIR_STRDUP_QUIET or VIR_STRNDUP_QUIET, but such usage is very rare
|
|
|
|
|
and usually considered a flaw.
|
|
|
|
|
</p>
|
|
|
|
|
|
2009-06-29 11:09:17 +00:00
|
|
|
<h2><a name="strbuf">Variable length string buffer</a></h2>
|
|
|
|
|
|
|
|
|
|
<p>
|
|
|
|
|
If there is a need for complex string concatenations, avoid using
|
|
|
|
|
the usual sequence of malloc/strcpy/strcat/snprintf functions and
|
2014-06-27 07:23:13 +00:00
|
|
|
make use of the virBuffer API described in virbuffer.h
|
2009-06-29 11:09:17 +00:00
|
|
|
</p>
|
|
|
|
|
|
2010-08-13 21:00:47 +00:00
|
|
|
<p>Typical usage is as follows:</p>
|
2009-06-29 11:09:17 +00:00
|
|
|
|
2010-11-12 14:33:00 +00:00
|
|
|
<pre>
|
2009-06-29 11:09:17 +00:00
|
|
|
char *
|
2010-11-12 14:33:00 +00:00
|
|
|
somefunction(...)
|
|
|
|
|
{
|
2009-06-29 11:09:17 +00:00
|
|
|
virBuffer buf = VIR_BUFFER_INITIALIZER;
|
|
|
|
|
|
|
|
|
|
...
|
|
|
|
|
|
|
|
|
|
virBufferAddLit(&buf, "<domain>\n");
|
2011-04-30 16:34:49 +00:00
|
|
|
virBufferAsprintf(&buf, " <memory>%d</memory>\n", memory);
|
2009-06-29 11:09:17 +00:00
|
|
|
...
|
|
|
|
|
virBufferAddLit(&buf, "</domain>\n");
|
|
|
|
|
|
2009-12-09 23:00:50 +00:00
|
|
|
...
|
2009-06-29 11:09:17 +00:00
|
|
|
|
2014-06-27 07:23:13 +00:00
|
|
|
if (virBufferCheckError(&buf) < 0)
|
2009-06-29 11:09:17 +00:00
|
|
|
return NULL;
|
|
|
|
|
|
|
|
|
|
return virBufferContentAndReset(&buf);
|
|
|
|
|
}
|
|
|
|
|
</pre>
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
<h2><a name="includes">Include files</a></h2>
|
|
|
|
|
|
|
|
|
|
<p>
|
|
|
|
|
There are now quite a large number of include files, both libvirt
|
|
|
|
|
internal and external, and system includes. To manage all this
|
|
|
|
|
complexity it's best to stick to the following general plan for all
|
|
|
|
|
*.c source files:
|
|
|
|
|
</p>
|
|
|
|
|
|
2010-11-12 14:33:00 +00:00
|
|
|
<pre>
|
2009-06-29 11:09:17 +00:00
|
|
|
/*
|
|
|
|
|
* Copyright notice
|
|
|
|
|
* ....
|
|
|
|
|
* ....
|
|
|
|
|
* ....
|
|
|
|
|
*
|
|
|
|
|
*/
|
|
|
|
|
|
|
|
|
|
#include <config.h> Must come first in every file.
|
|
|
|
|
|
|
|
|
|
#include <stdio.h> Any system includes you need.
|
|
|
|
|
#include <string.h>
|
|
|
|
|
#include <limits.h>
|
|
|
|
|
|
2012-09-20 12:41:15 +00:00
|
|
|
#if WITH_NUMACTL Some system includes aren't supported
|
2010-11-12 14:33:00 +00:00
|
|
|
# include <numa.h> everywhere so need these #if guards.
|
2009-06-29 11:09:17 +00:00
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
#include "internal.h" Include this first, after system includes.
|
|
|
|
|
|
|
|
|
|
#include "util.h" Any libvirt internal header files.
|
|
|
|
|
#include "buf.h"
|
|
|
|
|
|
2010-11-12 14:33:00 +00:00
|
|
|
static int
|
|
|
|
|
myInternalFunc() The actual code.
|
2009-06-29 11:09:17 +00:00
|
|
|
{
|
2010-11-12 14:33:00 +00:00
|
|
|
...
|
2009-06-29 11:09:17 +00:00
|
|
|
</pre>
|
|
|
|
|
|
|
|
|
|
<p>
|
2013-04-17 10:19:20 +00:00
|
|
|
Of particular note: <b>Do not</b> include libvirt/libvirt.h,
|
|
|
|
|
libvirt/virterror.h, libvirt/libvirt-qemu.h, or libvirt/libvirt-lxc.h.
|
|
|
|
|
They are included by "internal.h" already and there are some special reasons
|
|
|
|
|
why you cannot include these files explicitly. One of the special cases,
|
|
|
|
|
"libvirt/libvirt.h" is included prior to "internal.h" in "remote_protocol.x",
|
|
|
|
|
to avoid exposing *_LAST enum elements.
|
2009-06-29 11:09:17 +00:00
|
|
|
</p>
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
<h2><a name="printf">Printf-style functions</a></h2>
|
|
|
|
|
|
|
|
|
|
<p>
|
|
|
|
|
Whenever you add a new printf-style function, i.e., one with a format
|
|
|
|
|
string argument and following "..." in its prototype, be sure to use
|
|
|
|
|
gcc's printf attribute directive in the prototype. For example, here's
|
|
|
|
|
the one for virAsprintf, in util.h:
|
|
|
|
|
</p>
|
|
|
|
|
|
2010-11-12 14:33:00 +00:00
|
|
|
<pre>
|
|
|
|
|
int virAsprintf(char **strp, const char *fmt, ...)
|
|
|
|
|
ATTRIBUTE_FORMAT(printf, 2, 3);
|
2009-06-29 11:09:17 +00:00
|
|
|
</pre>
|
|
|
|
|
|
|
|
|
|
<p>
|
|
|
|
|
This makes it so gcc's -Wformat and -Wformat-security options can do
|
|
|
|
|
their jobs and cross-check format strings with the number and types
|
|
|
|
|
of arguments.
|
|
|
|
|
</p>
|
|
|
|
|
|
2010-08-18 23:31:39 +00:00
|
|
|
<p>
|
|
|
|
|
When printing to a string, consider using virBuffer for
|
|
|
|
|
incremental allocations, virAsprintf for a one-shot allocation,
|
|
|
|
|
and snprintf for fixed-width buffers. Do not use sprintf, even
|
|
|
|
|
if you can prove the buffer won't overflow, since gnulib does
|
|
|
|
|
not provide the same portability guarantees for sprintf as it
|
|
|
|
|
does for snprintf.
|
|
|
|
|
</p>
|
|
|
|
|
|
2010-03-08 15:26:30 +00:00
|
|
|
<h2><a name="goto">Use of goto</a></h2>
|
|
|
|
|
|
|
|
|
|
<p>
|
|
|
|
|
The use of goto is not forbidden, and goto is widely used
|
|
|
|
|
throughout libvirt. While the uncontrolled use of goto will
|
|
|
|
|
quickly lead to unmaintainable code, there is a place for it in
|
|
|
|
|
well structured code where its use increases readability and
|
|
|
|
|
maintainability. In general, if goto is used for error
|
|
|
|
|
recovery, it's likely to be ok, otherwise, be cautious or avoid
|
|
|
|
|
it all together.
|
|
|
|
|
</p>
|
|
|
|
|
|
|
|
|
|
<p>
|
|
|
|
|
The typical use of goto is to jump to cleanup code in the case
|
|
|
|
|
of a long list of actions, any of which may fail and cause the
|
|
|
|
|
entire operation to fail. In this case, a function will have a
|
|
|
|
|
single label at the end of the function. It's almost always ok
|
|
|
|
|
to use this style. In particular, if the cleanup code only
|
|
|
|
|
involves free'ing memory, then having multiple labels is
|
|
|
|
|
overkill. VIR_FREE() and every function named XXXFree() in
|
|
|
|
|
libvirt is required to handle NULL as its arg. Thus you can
|
|
|
|
|
safely call free on all the variables even if they were not yet
|
|
|
|
|
allocated (yes they have to have been initialized to NULL).
|
|
|
|
|
This is much simpler and clearer than having multiple labels.
|
|
|
|
|
</p>
|
|
|
|
|
|
|
|
|
|
<p>
|
|
|
|
|
There are a couple of signs that a particular use of goto is not
|
|
|
|
|
ok:
|
|
|
|
|
</p>
|
|
|
|
|
|
|
|
|
|
<ul>
|
|
|
|
|
<li>You're using multiple labels. If you find yourself using
|
|
|
|
|
multiple labels, you're strongly encouraged to rework your code
|
|
|
|
|
to eliminate all but one of them.</li>
|
|
|
|
|
<li>The goto jumps back up to a point above the current line of
|
|
|
|
|
code being executed. Please use some combination of looping
|
|
|
|
|
constructs to re-execute code instead; it's almost certainly
|
|
|
|
|
going to be more understandable by others. One well-known
|
|
|
|
|
exception to this rule is restarting an i/o operation following
|
|
|
|
|
EINTR.</li>
|
|
|
|
|
<li>The goto jumps down to an arbitrary place in the middle of a
|
|
|
|
|
function followed by further potentially failing calls. You
|
|
|
|
|
should almost certainly be using a conditional and a block
|
|
|
|
|
instead of a goto. Perhaps some of your function's logic would
|
|
|
|
|
be better pulled out into a helper function.</li>
|
|
|
|
|
</ul>
|
|
|
|
|
|
|
|
|
|
<p>
|
|
|
|
|
Although libvirt does not encourage the Linux kernel wind/unwind
|
|
|
|
|
style of multiple labels, there's a good general discussion of
|
|
|
|
|
the issue archived at
|
2010-11-12 14:33:00 +00:00
|
|
|
<a href="http://kerneltrap.org/node/553/2131">KernelTrap</a>
|
2010-03-08 15:26:30 +00:00
|
|
|
</p>
|
|
|
|
|
|
|
|
|
|
<p>
|
|
|
|
|
When using goto, please use one of these standard labels if it
|
|
|
|
|
makes sense:
|
|
|
|
|
</p>
|
|
|
|
|
|
2010-11-12 14:33:00 +00:00
|
|
|
<pre>
|
2010-03-08 15:26:30 +00:00
|
|
|
error: A path only taken upon return with an error code
|
|
|
|
|
cleanup: A path taken upon return with success code + optional error
|
|
|
|
|
no_memory: A path only taken upon return with an OOM error code
|
2010-08-13 21:00:47 +00:00
|
|
|
retry: If needing to jump upwards (e.g., retry on EINTR)
|
2010-11-12 14:33:00 +00:00
|
|
|
</pre>
|
2010-03-08 15:26:30 +00:00
|
|
|
|
2014-03-21 12:07:03 +00:00
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<p>
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Top-level labels should be indented by one space (putting them on
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the beginning of the line confuses function context detection in git):
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</p>
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<pre>
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int foo()
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{
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/* ... do stuff ... */
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cleanup:
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/* ... do other stuff ... */
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}
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</pre>
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2009-06-29 11:09:17 +00:00
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2010-03-09 16:59:25 +00:00
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<h2><a name="committers">Libvirt committer guidelines</a></h2>
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2009-06-29 11:09:17 +00:00
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<p>
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2010-03-09 00:02:44 +00:00
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The AUTHORS files indicates the list of people with commit access right
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2009-06-29 11:09:17 +00:00
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who can actually merge the patches.
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</p>
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<p>
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2010-03-09 16:59:25 +00:00
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The general rule for committing a patch is to make sure
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it has been reviewed
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properly in the mailing-list first, usually if a couple of people gave an
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2009-06-29 11:09:17 +00:00
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ACK or +1 to a patch and nobody raised an objection on the list it should
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2010-03-09 16:59:25 +00:00
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be good to go. If the patch touches a part of the code where you're not
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the main maintainer, or where you do not have a very clear idea of
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2010-03-09 00:02:44 +00:00
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how things work, it's better
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to wait for a more authoritative feedback though. Before committing, please
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also rebuild locally, run 'make check syntax-check', and make sure you
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don't raise errors. Try to look for warnings too; for example,
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configure with
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2010-03-13 14:04:34 +00:00
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</p>
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2010-03-09 00:02:44 +00:00
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<pre>
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2010-11-12 14:33:00 +00:00
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--enable-compile-warnings=error
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2010-03-09 00:02:44 +00:00
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</pre>
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2010-03-13 14:04:34 +00:00
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<p>
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2009-06-29 11:09:17 +00:00
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which adds -Werror to compile flags, so no warnings get missed
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</p>
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<p>
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2010-03-09 00:02:44 +00:00
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An exception to 'review and approval on the list first' is fixing failures
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2009-06-29 11:09:17 +00:00
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to build:
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</p>
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<ul>
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2010-03-09 00:02:44 +00:00
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<li>if a recently committed patch breaks compilation on a platform
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or for a given driver, then it's fine to commit a minimal fix
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2009-11-06 15:04:19 +00:00
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directly without getting the review feedback first</li>
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2010-01-30 11:35:04 +00:00
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<li>if make check or make syntax-check breaks, if there is
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2009-11-06 15:04:19 +00:00
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an obvious fix, it's fine to commit immediately.
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The patch should still be sent to the list (or tell what the fix was if
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2010-03-09 00:02:44 +00:00
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trivial), and 'make check syntax-check' should pass too, before committing
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2009-11-06 15:04:19 +00:00
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anything</li>
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2009-06-29 11:09:17 +00:00
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<li>
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2009-11-06 15:04:19 +00:00
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fixes for documentation and code comments can be managed
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in the same way, but still make sure they get reviewed if non-trivial.
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2009-06-29 11:09:17 +00:00
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</li>
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</ul>
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</body>
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</html>
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