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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>LLVM Developer Policy</title>
<link rel="stylesheet" href="llvm.css" type="text/css">
</head>
<body>
<h1>LLVM Developer Policy</h1>
<ol>
<li><a href="#introduction">Introduction</a></li>
<li><a href="#policies">Developer Policies</a>
<ol>
<li><a href="#informed">Stay Informed</a></li>
<li><a href="#patches">Making a Patch</a></li>
<li><a href="#reviews">Code Reviews</a></li>
<li><a href="#owners">Code Owners</a></li>
<li><a href="#testcases">Test Cases</a></li>
<li><a href="#quality">Quality</a></li>
<li><a href="#commitaccess">Obtaining Commit Access</a></li>
<li><a href="#newwork">Making a Major Change</a></li>
<li><a href="#incremental">Incremental Development</a></li>
<li><a href="#attribution">Attribution of Changes</a></li>
</ol></li>
<li><a href="#clp">Copyright, License, and Patents</a>
<ol>
<li><a href="#copyright">Copyright</a></li>
<li><a href="#license">License</a></li>
<li><a href="#patents">Patents</a></li>
</ol></li>
</ol>
<div class="doc_author">Written by the LLVM Oversight Team</div>
<!--=========================================================================-->
<h2><a name="introduction">Introduction</a></h2>
<!--=========================================================================-->
<div>
<p>This document contains the LLVM Developer Policy which defines the project's
policy towards developers and their contributions. The intent of this policy
is to eliminate miscommunication, rework, and confusion that might arise from
the distributed nature of LLVM's development. By stating the policy in clear
terms, we hope each developer can know ahead of time what to expect when
making LLVM contributions. This policy covers all llvm.org subprojects,
including Clang, LLDB, libc++, etc.</p>
<p>This policy is also designed to accomplish the following objectives:</p>
<ol>
<li>Attract both users and developers to the LLVM project.</li>
<li>Make life as simple and easy for contributors as possible.</li>
<li>Keep the top of Subversion trees as stable as possible.</li>
<li>Establish awareness of the project's <a href="#clp">copyright,
license, and patent policies</a> with contributors to the project.</li>
</ol>
<p>This policy is aimed at frequent contributors to LLVM. People interested in
contributing one-off patches can do so in an informal way by sending them to
the
<a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits">llvm-commits
mailing list</a> and engaging another developer to see it through the
process.</p>
</div>
<!--=========================================================================-->
<h2><a name="policies">Developer Policies</a></h2>
<!--=========================================================================-->
<div>
<p>This section contains policies that pertain to frequent LLVM developers. We
always welcome <a href="#patches">one-off patches</a> from people who do not
routinely contribute to LLVM, but we expect more from frequent contributors
to keep the system as efficient as possible for everyone. Frequent LLVM
contributors are expected to meet the following requirements in order for
LLVM to maintain a high standard of quality.<p>
<!-- _______________________________________________________________________ -->
<h3><a name="informed">Stay Informed</a></h3>
<div>
<p>Developers should stay informed by reading at least the "dev" mailing list
for the projects you are interested in, such as
<a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">llvmdev</a> for
LLVM, <a href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev">cfe-dev</a>
for Clang, or <a
href="http://lists.cs.uiuc.edu/mailman/listinfo/lldb-dev">lldb-dev</a>
for LLDB. If you are doing anything more than just casual work on LLVM, it
is suggested that you also subscribe to the "commits" mailing list for the
subproject you're interested in, such as
<a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits">llvm-commits</a>,
<a href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits">cfe-commits</a>,
or <a href="http://lists.cs.uiuc.edu/mailman/listinfo/lldb-commits">lldb-commits</a>.
Reading the "commits" list and paying attention to changes being made by
others is a good way to see what other people are interested in and watching
the flow of the project as a whole.</p>
<p>We recommend that active developers register an email account with
<a href="http://llvm.org/bugs/">LLVM Bugzilla</a> and preferably subscribe to
the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmbugs">llvm-bugs</a>
email list to keep track of bugs and enhancements occurring in LLVM. We
really appreciate people who are proactive at catching incoming bugs in their
components and dealing with them promptly.</p>
</div>
<!-- _______________________________________________________________________ -->
<h3><a name="patches">Making a Patch</a></h3>
<div>
<p>When making a patch for review, the goal is to make it as easy for the
reviewer to read it as possible. As such, we recommend that you:</p>
<ol>
<li>Make your patch against the Subversion trunk, not a branch, and not an old
version of LLVM. This makes it easy to apply the patch. For information
on how to check out SVN trunk, please see the <a
href="GettingStarted.html#checkout">Getting Started Guide</a>.</li>
<li>Similarly, patches should be submitted soon after they are generated. Old
patches may not apply correctly if the underlying code changes between the
time the patch was created and the time it is applied.</li>
<li>Patches should be made with <tt>svn diff</tt>, or similar. If you use
a different tool, make sure it uses the <tt>diff -u</tt> format and
that it doesn't contain clutter which makes it hard to read.</li>
<li>If you are modifying generated files, such as the top-level
<tt>configure</tt> script, please separate out those changes into
a separate patch from the rest of your changes.</li>
</ol>
<p>When sending a patch to a mailing list, it is a good idea to send it as an
<em>attachment</em> to the message, not embedded into the text of the
message. This ensures that your mailer will not mangle the patch when it
sends it (e.g. by making whitespace changes or by wrapping lines).</p>
<p><em>For Thunderbird users:</em> Before submitting a patch, please open
<em>Preferences → Advanced → General → Config Editor</em>,
find the key <tt>mail.content_disposition_type</tt>, and set its value to
<tt>1</tt>. Without this setting, Thunderbird sends your attachment using
<tt>Content-Disposition: inline</tt> rather than <tt>Content-Disposition:
attachment</tt>. Apple Mail gamely displays such a file inline, making it
difficult to work with for reviewers using that program.</p>
</div>
<!-- _______________________________________________________________________ -->
<h3><a name="reviews">Code Reviews</a></h3>
<div>
<p>LLVM has a code review policy. Code review is one way to increase the quality
of software. We generally follow these policies:</p>
<ol>
<li>All developers are required to have significant changes reviewed before
they are committed to the repository.</li>
<li>Code reviews are conducted by email, usually on the llvm-commits
list.</li>
<li>Code can be reviewed either before it is committed or after. We expect
major changes to be reviewed before being committed, but smaller changes
(or changes where the developer owns the component) can be reviewed after
commit.</li>
<li>The developer responsible for a code change is also responsible for making
all necessary review-related changes.</li>
<li>Code review can be an iterative process, which continues until the patch
is ready to be committed.</li>
</ol>
<p>Developers should participate in code reviews as both reviewers and
reviewees. If someone is kind enough to review your code, you should return
the favor for someone else. Note that anyone is welcome to review and give
feedback on a patch, but only people with Subversion write access can approve
it.</p>
</div>
<!-- _______________________________________________________________________ -->
<h3><a name="owners">Code Owners</a></h3>
<div>
<p>The LLVM Project relies on two features of its process to maintain rapid
development in addition to the high quality of its source base: the
combination of code review plus post-commit review for trusted maintainers.
Having both is a great way for the project to take advantage of the fact that
most people do the right thing most of the time, and only commit patches
without pre-commit review when they are confident they are right.</p>
<p>The trick to this is that the project has to guarantee that all patches that
are committed are reviewed after they go in: you don't want everyone to
assume someone else will review it, allowing the patch to go unreviewed. To
solve this problem, we have a notion of an 'owner' for a piece of the code.
The sole responsibility of a code owner is to ensure that a commit to their
area of the code is appropriately reviewed, either by themself or by someone
else. The current code owners are:</p>
<ol>
<li><b>Evan Cheng</b>: Code generator and all targets.</li>
<li><b>Greg Clayton</b>: LLDB.</li>
<li><b>Doug Gregor</b>: Clang Frontend Libraries.</li>
<li><b>Howard Hinnant</b>: libc++.</li>
<li><b>Anton Korobeynikov</b>: Exception handling, debug information, and
Windows codegen.</li>
<li><b>Ted Kremenek</b>: Clang Static Analyzer.</li>
<li><b>Chris Lattner</b>: Everything not covered by someone else.</li>
<li><b>John McCall</b>: Clang LLVM IR generation.</li>
<li><b>Jakob Olesen</b>: Register allocators and TableGen.</li>
<li><b>Duncan Sands</b>: dragonegg and llvm-gcc 4.2.</li>
<li><b>Peter Collingbourne</b>: libclc.</li>
<li><b>Tobias Grosser</b>: polly.</li>
</ol>
<p>Note that code ownership is completely different than reviewers: anyone can
review a piece of code, and we welcome code review from anyone who is
interested. Code owners are the "last line of defense" to guarantee that all
patches that are committed are actually reviewed.</p>
<p>Being a code owner is a somewhat unglamorous position, but it is incredibly
important for the ongoing success of the project. Because people get busy,
interests change, and unexpected things happen, code ownership is purely
opt-in, and anyone can choose to resign their "title" at any time. For now,
we do not have an official policy on how one gets elected to be a code
owner.</p>
</div>
<!-- _______________________________________________________________________ -->
<h3><a name="testcases">Test Cases</a></h3>
<div>
<p>Developers are required to create test cases for any bugs fixed and any new
features added. Some tips for getting your testcase approved:</p>
<ol>
<li>All feature and regression test cases are added to the
<tt>llvm/test</tt> directory. The appropriate sub-directory should be
selected (see the <a href=
|
