mirror of
				https://github.com/c64scene-ar/llvm-6502.git
				synced 2025-11-04 05:17:07 +00:00 
			
		
		
		
	git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@141372 91177308-0d34-0410-b5e6-96231b3b80d8
		
			
				
	
	
		
			623 lines
		
	
	
		
			29 KiB
		
	
	
	
		
			HTML
		
	
	
	
	
	
			
		
		
	
	
			623 lines
		
	
	
		
			29 KiB
		
	
	
	
		
			HTML
		
	
	
	
	
	
<!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, 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>
 | 
						|
</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>
 | 
						|
</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="TestingGuide.html">Testing Guide</a> for
 | 
						|
      details).</li>
 | 
						|
 | 
						|
  <li>Test cases should be written in <a href="LangRef.html">LLVM assembly
 | 
						|
      language</a> unless the feature or regression being tested requires
 | 
						|
      another language (e.g. the bug being fixed or feature being implemented is
 | 
						|
      in the llvm-gcc C++ front-end, in which case it must be written in
 | 
						|
      C++).</li>
 | 
						|
 | 
						|
  <li>Test cases, especially for regressions, should be reduced as much as
 | 
						|
      possible, by <a href="Bugpoint.html">bugpoint</a> or manually. It is
 | 
						|
      unacceptable to place an entire failing program into <tt>llvm/test</tt> as
 | 
						|
      this creates a <i>time-to-test</i> burden on all developers. Please keep
 | 
						|
      them short.</li>
 | 
						|
</ol>
 | 
						|
  
 | 
						|
<p>Note that llvm/test and clang/test are designed for regression and small
 | 
						|
   feature tests only. More extensive test cases (e.g., entire applications,
 | 
						|
   benchmarks, etc)
 | 
						|
   should be added to the <tt>llvm-test</tt> test suite.  The llvm-test suite is
 | 
						|
   for coverage (correctness, performance, etc) testing, not feature or
 | 
						|
   regression testing.</p>
 | 
						|
</div>
 | 
						|
 | 
						|
<!-- _______________________________________________________________________ -->
 | 
						|
<h3><a name="quality">Quality</a></h3>
 | 
						|
<div>
 | 
						|
<p>The minimum quality standards that any change must satisfy before being
 | 
						|
   committed to the main development branch are:</p>
 | 
						|
 | 
						|
<ol>
 | 
						|
  <li>Code must adhere to the <a href="CodingStandards.html">LLVM Coding
 | 
						|
      Standards</a>.</li>
 | 
						|
 | 
						|
  <li>Code must compile cleanly (no errors, no warnings) on at least one
 | 
						|
      platform.</li>
 | 
						|
 | 
						|
  <li>Bug fixes and new features should <a href="#testcases">include a
 | 
						|
      testcase</a> so we know if the fix/feature ever regresses in the
 | 
						|
      future.</li>
 | 
						|
 | 
						|
  <li>Code must pass the <tt>llvm/test</tt> test suite.</li>
 | 
						|
 | 
						|
  <li>The code must not cause regressions on a reasonable subset of llvm-test,
 | 
						|
      where "reasonable" depends on the contributor's judgement and the scope of
 | 
						|
      the change (more invasive changes require more testing). A reasonable
 | 
						|
      subset might be something like
 | 
						|
      "<tt>llvm-test/MultiSource/Benchmarks</tt>".</li>
 | 
						|
</ol>
 | 
						|
 | 
						|
<p>Additionally, the committer is responsible for addressing any problems found
 | 
						|
   in the future that the change is responsible for.  For example:</p>
 | 
						|
 | 
						|
<ul>
 | 
						|
  <li>The code should compile cleanly on all supported platforms.</li>
 | 
						|
 | 
						|
  <li>The changes should not cause any correctness regressions in the
 | 
						|
      <tt>llvm-test</tt> suite and must not cause any major performance
 | 
						|
      regressions.</li>
 | 
						|
 | 
						|
  <li>The change set should not cause performance or correctness regressions for
 | 
						|
      the LLVM tools.</li>
 | 
						|
 | 
						|
  <li>The changes should not cause performance or correctness regressions in
 | 
						|
      code compiled by LLVM on all applicable targets.</li>
 | 
						|
 | 
						|
  <li>You are expected to address any <a href="http://llvm.org/bugs/">bugzilla
 | 
						|
      bugs</a> that result from your change.</li>
 | 
						|
</ul>
 | 
						|
  
 | 
						|
<p>We prefer for this to be handled before submission but understand that it
 | 
						|
   isn't possible to test all of this for every submission.  Our build bots and
 | 
						|
   nightly testing infrastructure normally finds these problems.  A good rule of
 | 
						|
   thumb is to check the nightly testers for regressions the day after your
 | 
						|
   change.  Build bots will directly email you if a group of commits that
 | 
						|
   included yours caused a failure.  You are expected to check the build bot
 | 
						|
   messages to see if they are your fault and, if so, fix the breakage.</p>
 | 
						|
 | 
						|
<p>Commits that violate these quality standards (e.g. are very broken) may be
 | 
						|
   reverted. This is necessary when the change blocks other developers from
 | 
						|
   making progress. The developer is welcome to re-commit the change after the
 | 
						|
   problem has been fixed.</p>
 | 
						|
</div>
 | 
						|
 | 
						|
<!-- _______________________________________________________________________ -->
 | 
						|
<h3><a name="commitaccess">Obtaining Commit Access</a></h3>
 | 
						|
<div>
 | 
						|
 | 
						|
<p>We grant commit access to contributors with a track record of submitting high
 | 
						|
   quality patches.  If you would like commit access, please send an email to
 | 
						|
   <a href="mailto:sabre@nondot.org">Chris</a> with the following
 | 
						|
   information:</p>
 | 
						|
 | 
						|
<ol>
 | 
						|
  <li>The user name you want to commit with, e.g. "hacker".</li>
 | 
						|
 | 
						|
  <li>The full name and email address you want message to llvm-commits to come
 | 
						|
      from, e.g. "J. Random Hacker <hacker@yoyodyne.com>".</li>
 | 
						|
 | 
						|
  <li>A "password hash" of the password you want to use, e.g. "2ACR96qjUqsyM".  
 | 
						|
      Note that you don't ever tell us what your password is, you just give it
 | 
						|
      to us in an encrypted form.  To get this, run "htpasswd" (a utility that
 | 
						|
      comes with apache) in crypt mode (often enabled with "-d"), or find a web
 | 
						|
      page that will do it for you.</li>
 | 
						|
</ol>
 | 
						|
 | 
						|
<p>Once you've been granted commit access, you should be able to check out an
 | 
						|
   LLVM tree with an SVN URL of "https://username@llvm.org/..." instead of the
 | 
						|
   normal anonymous URL of "http://llvm.org/...".  The first time you commit
 | 
						|
   you'll have to type in your password.  Note that you may get a warning from
 | 
						|
   SVN about an untrusted key, you can ignore this.  To verify that your commit
 | 
						|
   access works, please do a test commit (e.g. change a comment or add a blank
 | 
						|
   line).  Your first commit to a repository may require the autogenerated email
 | 
						|
   to be approved by a mailing list.  This is normal, and will be done when
 | 
						|
   the mailing list owner has time.</p>
 | 
						|
 | 
						|
<p>If you have recently been granted commit access, these policies apply:</p>
 | 
						|
 | 
						|
<ol>
 | 
						|
  <li>You are granted <i>commit-after-approval</i> to all parts of LLVM.  To get
 | 
						|
      approval, submit a <a href="#patches">patch</a> to
 | 
						|
      <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits">llvm-commits</a>.
 | 
						|
      When approved you may commit it yourself.</li>
 | 
						|
 | 
						|
  <li>You are allowed to commit patches without approval which you think are
 | 
						|
      obvious. This is clearly a subjective decision — we simply expect
 | 
						|
      you to use good judgement.  Examples include: fixing build breakage,
 | 
						|
      reverting obviously broken patches, documentation/comment changes, any
 | 
						|
      other minor changes.</li>
 | 
						|
 | 
						|
  <li>You are allowed to commit patches without approval to those portions of
 | 
						|
      LLVM that you have contributed or maintain (i.e., have been assigned
 | 
						|
      responsibility for), with the proviso that such commits must not break the
 | 
						|
      build.  This is a "trust but verify" policy and commits of this nature are
 | 
						|
      reviewed after they are committed.</li>
 | 
						|
 | 
						|
  <li>Multiple violations of these policies or a single egregious violation may
 | 
						|
      cause commit access to be revoked.</li>
 | 
						|
</ol>
 | 
						|
 | 
						|
<p>In any case, your changes are still subject to <a href="#reviews">code
 | 
						|
   review</a> (either before or after they are committed, depending on the
 | 
						|
   nature of the change).  You are encouraged to review other peoples' patches
 | 
						|
   as well, but you aren't required to.</p>
 | 
						|
</div>
 | 
						|
 | 
						|
<!-- _______________________________________________________________________ -->
 | 
						|
<h3><a name="newwork">Making a Major Change</a></h3>
 | 
						|
<div>
 | 
						|
<p>When a developer begins a major new project with the aim of contributing it
 | 
						|
   back to LLVM, s/he should inform the community with an email to
 | 
						|
   the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">llvmdev</a>
 | 
						|
   email list, to the extent possible. The reason for this is to:
 | 
						|
 | 
						|
<ol>
 | 
						|
  <li>keep the community informed about future changes to LLVM, </li>
 | 
						|
 | 
						|
  <li>avoid duplication of effort by preventing multiple parties working on the
 | 
						|
      same thing and not knowing about it, and</li>
 | 
						|
 | 
						|
  <li>ensure that any technical issues around the proposed work are discussed
 | 
						|
      and resolved before any significant work is done.</li>
 | 
						|
</ol>
 | 
						|
  
 | 
						|
<p>The design of LLVM is carefully controlled to ensure that all the pieces fit
 | 
						|
   together well and are as consistent as possible. If you plan to make a major
 | 
						|
   change to the way LLVM works or want to add a major new extension, it is a
 | 
						|
   good idea to get consensus with the development community before you start
 | 
						|
   working on it.</p>
 | 
						|
  
 | 
						|
<p>Once the design of the new feature is finalized, the work itself should be
 | 
						|
   done as a series of <a href="#incremental">incremental changes</a>, not as a
 | 
						|
   long-term development branch.</p>
 | 
						|
</div>
 | 
						|
 | 
						|
<!-- _______________________________________________________________________ -->
 | 
						|
<h3><a name="incremental">Incremental Development</a></h3>
 | 
						|
<div>
 | 
						|
<p>In the LLVM project, we do all significant changes as a series of incremental
 | 
						|
   patches.  We have a strong dislike for huge changes or long-term development
 | 
						|
   branches.  Long-term development branches have a number of drawbacks:</p>
 | 
						|
 | 
						|
<ol>
 | 
						|
  <li>Branches must have mainline merged into them periodically.  If the branch
 | 
						|
      development and mainline development occur in the same pieces of code,
 | 
						|
      resolving merge conflicts can take a lot of time.</li>
 | 
						|
 | 
						|
  <li>Other people in the community tend to ignore work on branches.</li>
 | 
						|
 | 
						|
  <li>Huge changes (produced when a branch is merged back onto mainline) are
 | 
						|
      extremely difficult to <a href="#reviews">code review</a>.</li>
 | 
						|
 | 
						|
  <li>Branches are not routinely tested by our nightly tester
 | 
						|
      infrastructure.</li>
 | 
						|
 | 
						|
  <li>Changes developed as monolithic large changes often don't work until the
 | 
						|
      entire set of changes is done.  Breaking it down into a set of smaller
 | 
						|
      changes increases the odds that any of the work will be committed to the
 | 
						|
      main repository.</li>
 | 
						|
</ol>    
 | 
						|
  
 | 
						|
<p>To address these problems, LLVM uses an incremental development style and we
 | 
						|
   require contributors to follow this practice when making a large/invasive
 | 
						|
   change.  Some tips:</p>
 | 
						|
 | 
						|
<ul>
 | 
						|
  <li>Large/invasive changes usually have a number of secondary changes that are
 | 
						|
      required before the big change can be made (e.g. API cleanup, etc).  These
 | 
						|
      sorts of changes can often be done before the major change is done,
 | 
						|
      independently of that work.</li>
 | 
						|
 | 
						|
  <li>The remaining inter-related work should be decomposed into unrelated sets
 | 
						|
      of changes if possible.  Once this is done, define the first increment and
 | 
						|
      get consensus on what the end goal of the change is.</li>
 | 
						|
 | 
						|
  <li>Each change in the set can be stand alone (e.g. to fix a bug), or part of
 | 
						|
      a planned series of changes that works towards the development goal.</li>
 | 
						|
    
 | 
						|
  <li>Each change should be kept as small as possible. This simplifies your work
 | 
						|
      (into a logical progression), simplifies code review and reduces the
 | 
						|
      chance that you will get negative feedback on the change. Small increments
 | 
						|
      also facilitate the maintenance of a high quality code base.</li>
 | 
						|
 | 
						|
  <li>Often, an independent precursor to a big change is to add a new API and
 | 
						|
      slowly migrate clients to use the new API.  Each change to use the new API
 | 
						|
      is often "obvious" and can be committed without review.  Once the new API
 | 
						|
      is in place and used, it is much easier to replace the underlying
 | 
						|
      implementation of the API.  This implementation change is logically
 | 
						|
      separate from the API change.</li>
 | 
						|
</ul>
 | 
						|
  
 | 
						|
<p>If you are interested in making a large change, and this scares you, please
 | 
						|
   make sure to first <a href="#newwork">discuss the change/gather consensus</a>
 | 
						|
   then ask about the best way to go about making the change.</p>
 | 
						|
</div>
 | 
						|
 | 
						|
<!-- _______________________________________________________________________ -->
 | 
						|
<h3><a name="attribution">Attribution of Changes</a></h3>
 | 
						|
<div>
 | 
						|
<p>We believe in correct attribution of contributions to their contributors.
 | 
						|
   However, we do not want the source code to be littered with random
 | 
						|
   attributions "this code written by J. Random Hacker" (this is noisy and
 | 
						|
   distracting).  In practice, the revision control system keeps a perfect
 | 
						|
   history of who changed what, and the CREDITS.txt file describes higher-level
 | 
						|
   contributions.  If you commit a patch for someone else, please say "patch
 | 
						|
   contributed by J. Random Hacker!" in the commit message.</p>
 | 
						|
 | 
						|
<p>Overall, please do not add contributor names to the source code.</p>
 | 
						|
</div>
 | 
						|
 | 
						|
</div>
 | 
						|
 | 
						|
<!--=========================================================================-->
 | 
						|
<h2>
 | 
						|
  <a name="clp">Copyright, License, and Patents</a>
 | 
						|
</h2>
 | 
						|
<!--=========================================================================-->
 | 
						|
 | 
						|
<div>
 | 
						|
<p>This section addresses the issues of copyright, license and patents for the
 | 
						|
   LLVM project.  The copyright holder for the code is held by the individual
 | 
						|
   contributors of the code and the terms of its license to LLVM users and 
 | 
						|
   developers is the
 | 
						|
   <a href="http://www.opensource.org/licenses/UoI-NCSA.php">University of 
 | 
						|
   Illinois/NCSA Open Source License</a>.</p>
 | 
						|
 | 
						|
<div class="doc_notes">
 | 
						|
<p style="text-align:center;font-weight:bold">NOTE: This section deals with
 | 
						|
   legal matters but does not provide legal advice.  We are not lawyers, please
 | 
						|
   seek legal counsel from an attorney.</p>
 | 
						|
</div>
 | 
						|
 | 
						|
<!-- _______________________________________________________________________ -->
 | 
						|
<h3><a name="copyright">Copyright</a></h3>
 | 
						|
<div>
 | 
						|
 | 
						|
<p>The LLVM project does not require copyright assignments, which means that the
 | 
						|
   copyright for the code in the project is held by its respective contributors
 | 
						|
   who have each agreed to release their contributed code under the terms of the
 | 
						|
   <a href="#license">LLVM License</a>.</p>
 | 
						|
   
 | 
						|
<p>An implication of this is that the LLVM license is unlikely to ever change:
 | 
						|
   changing it would require tracking down all the contributors to LLVM and
 | 
						|
   getting them to agree that a license change is acceptable for their
 | 
						|
   contribution.  Since there are no plans to change the license, this is not a
 | 
						|
   cause for concern.</p>
 | 
						|
   
 | 
						|
<p>As a contributor to the project, this means that you (or your company) retain
 | 
						|
   ownership of the code you contribute, that it cannot be used in a way that
 | 
						|
   contradicts the license (which is a liberal BSD-style license), and that the
 | 
						|
   license for your contributions won't change without your approval in the
 | 
						|
   future.</p>
 | 
						|
   
 | 
						|
</div>
 | 
						|
 | 
						|
<!-- _______________________________________________________________________ -->
 | 
						|
<h3><a name="license">License</a></h3>
 | 
						|
<div>
 | 
						|
<p>We intend to keep LLVM perpetually open source and to use a liberal open
 | 
						|
   source license. All of the code in LLVM is available under the
 | 
						|
   <a href="http://www.opensource.org/licenses/UoI-NCSA.php">University of
 | 
						|
   Illinois/NCSA Open Source License</a>, which boils down to this:</p>
 | 
						|
 | 
						|
<ul>
 | 
						|
  <li>You can freely distribute LLVM.</li>
 | 
						|
  <li>You must retain the copyright notice if you redistribute LLVM.</li>
 | 
						|
  <li>Binaries derived from LLVM must reproduce the copyright notice (e.g. in an
 | 
						|
      included readme file).</li>
 | 
						|
  <li>You can't use our names to promote your LLVM derived products.</li>
 | 
						|
  <li>There's no warranty on LLVM at all.</li>
 | 
						|
</ul>
 | 
						|
  
 | 
						|
<p>We believe this fosters the widest adoption of LLVM because it <b>allows
 | 
						|
   commercial products to be derived from LLVM</b> with few restrictions and
 | 
						|
   without a requirement for making any derived works also open source (i.e.
 | 
						|
   LLVM's license is not a "copyleft" license like the GPL). We suggest that you
 | 
						|
   read the <a href="http://www.opensource.org/licenses/UoI-NCSA.php">License</a>
 | 
						|
   if further clarification is needed.</p>
 | 
						|
   
 | 
						|
<p>In addition to the UIUC license, the runtime library components of LLVM
 | 
						|
   (<b>compiler_rt and libc++</b>) are also licensed under the <a
 | 
						|
   href="http://www.opensource.org/licenses/mit-license.php">MIT license</a>,
 | 
						|
   which does not contain the binary redistribution clause.  As a user of these
 | 
						|
   runtime libraries, it means that you can choose to use the code under either
 | 
						|
   license (and thus don't need the binary redistribution clause), and as a
 | 
						|
   contributor to the code that you agree that any contributions to these
 | 
						|
   libraries be licensed under both licenses.  We feel that this is important
 | 
						|
   for runtime libraries, because they are implicitly linked into applications
 | 
						|
   and therefore should not subject those applications to the binary
 | 
						|
   redistribution clause. This also means that it is ok to move code from (e.g.)
 | 
						|
   libc++ to the LLVM core without concern, but that code cannot be moved from
 | 
						|
   the LLVM core to libc++ without the copyright owner's permission.
 | 
						|
</p>
 | 
						|
 | 
						|
<p>Note that the LLVM Project does distribute llvm-gcc, <b>which is GPL.</b>
 | 
						|
   This means that anything "linked" into llvm-gcc must itself be compatible
 | 
						|
   with the GPL, and must be releasable under the terms of the GPL.  This
 | 
						|
   implies that <b>any code linked into llvm-gcc and distributed to others may
 | 
						|
   be subject to the viral aspects of the GPL</b> (for example, a proprietary
 | 
						|
   code generator linked into llvm-gcc must be made available under the GPL).
 | 
						|
   This is not a problem for code already distributed under a more liberal
 | 
						|
   license (like the UIUC license), and does not affect code generated by
 | 
						|
   llvm-gcc.  It may be a problem if you intend to base commercial development
 | 
						|
   on llvm-gcc without redistributing your source code.</p>
 | 
						|
  
 | 
						|
<p>We have no plans to change the license of LLVM.  If you have questions or
 | 
						|
   comments about the license, please contact the
 | 
						|
   <a href="mailto:llvmdev@cs.uiuc.edu">LLVM Developer's Mailing List</a>.</p>
 | 
						|
</div>
 | 
						|
 | 
						|
<!-- _______________________________________________________________________ -->
 | 
						|
<h3><a name="patents">Patents</a></h3>
 | 
						|
<div>
 | 
						|
<p>To the best of our knowledge, LLVM does not infringe on any patents (we have
 | 
						|
   actually removed code from LLVM in the past that was found to infringe).
 | 
						|
   Having code in LLVM that infringes on patents would violate an important goal
 | 
						|
   of the project by making it hard or impossible to reuse the code for
 | 
						|
   arbitrary purposes (including commercial use).</p>
 | 
						|
   
 | 
						|
<p>When contributing code, we expect contributors to notify us of any potential
 | 
						|
   for patent-related trouble with their changes.  If you or your employer own
 | 
						|
   the rights to a patent and would like to contribute code to LLVM that relies
 | 
						|
   on it, we require that the copyright owner sign an agreement that allows any
 | 
						|
   other user of LLVM to freely use your patent.  Please contact
 | 
						|
   the <a href="mailto:llvm-oversight@cs.uiuc.edu">oversight group</a> for more
 | 
						|
   details.</p>
 | 
						|
</div>
 | 
						|
 | 
						|
</div>
 | 
						|
 | 
						|
<!-- *********************************************************************** -->
 | 
						|
<hr>
 | 
						|
<address>
 | 
						|
  <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
 | 
						|
  src="http://jigsaw.w3.org/css-validator/images/vcss-blue" alt="Valid CSS"></a>
 | 
						|
  <a href="http://validator.w3.org/check/referer"><img
 | 
						|
  src="http://www.w3.org/Icons/valid-html401-blue" alt="Valid HTML 4.01"></a>
 | 
						|
  Written by the 
 | 
						|
  <a href="mailto:llvm-oversight@cs.uiuc.edu">LLVM Oversight Group</a><br>
 | 
						|
  <a href="http://llvm.org/">The LLVM Compiler Infrastructure</a><br>
 | 
						|
  Last modified: $Date$
 | 
						|
</address>
 | 
						|
</body>
 | 
						|
</html>
 |