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16<h1>Getting Involved with the Clang Project</h1>
17
18<p>Once you have <a href="get_started.html">checked out and built</a> clang and
19played around with it, you might be wondering what you can do to make it better
20and contribute to its development.  Alternatively, maybe you just want to follow
21the development of the project to see it progress.
22</p>
23
24<h2>Contribute</h2>
25
26See the <a href="hacking.html">hacking</a> document for information on how
27to author patches.
28
29<h2>Follow what's going on</h2>
30
31<p>Clang is a subproject of the <a href="https://llvm.org">LLVM Project</a>
32and has a Discourse forum and mailing list:</p>
33
34<ul>
35<li><a href="https://lists.llvm.org/mailman/listinfo/cfe-commits">cfe-commits
36</a> - This list is for patch submission/discussion.</li>
37
38<li><a href="https://discourse.llvm.org/c/clang/6">Clang Frontend Discourse forum</a> -
39This forum is for everything else Clang related (questions and answers, design
40discussions, etc).</li>
41
42</ul>
43
44<p>The most common way to talk with other developers on the project is through
45the <a href="https://discourse.llvm.org/c/clang/6">Clang Frontend Discourse forum
46</a>.  The clang forum is a very friendly place and we welcome
47newcomers.  In addition to the forum, a significant amount of design
48discussion takes place on the <a
49href="https://lists.llvm.org/mailman/listinfo/cfe-commits">cfe-commits mailing
50list</a>.  All of these lists have archives, so you can browse through previous
51discussions or follow the list development on the web if you prefer.</p>
52
53<p>If you're looking for something to work on, check out our <a
54href="OpenProjects.html">Open Projects</a> page or look through the <a
55href="https://github.com/llvm/llvm-project/issues/">LLVM bug tracker</a>.</p>
56
57<h2 id="criteria">Contributing Extensions to Clang</h2>
58
59<p>Clang is designed to support experimentation,
60allowing programmers to easily extend the compiler to support great
61new language features and tools. At some point, the authors of these
62extensions may propose that the extensions become a part of Clang
63itself, to benefit the whole Clang community. However, extensions
64(particularly language extensions) have long-term maintenance costs
65for Clang. The benefits of the extension need to be evaluated against
66these costs. The Clang project uses the following criteria for this
67evaluation:</p>
68
69<ol>
70  <li>Evidence of a significant user community: This is based on a number of
71  factors, including an existing user community, the perceived likelihood that
72  users would adopt such a feature if it were available, and any secondary
73  effects that come from, e.g., a library adopting the feature and providing
74  benefits to its users.</li>
75
76  <li>A specific need to reside within the Clang tree: There are some extensions
77  that would be better expressed as a separate tool, and should remain as
78  separate tools even if they end up being hosted as part of the LLVM umbrella
79  project.</li>
80
81  <li>A specification: The specification must be sufficient to understand the
82  design of the feature as well as interpret the meaning of specific examples.
83  The specification should be detailed enough that another compiler vendor
84  could implement the feature.</li>
85
86  <li>Representation within the appropriate governing organization: For
87  extensions to a language governed by a standards committee (C, C++, OpenCL),
88  the extension itself must have an active proposal and proponent within that
89  committee and have a reasonable chance of acceptance. Clang should drive the
90  standard, not diverge from it. This criterion does not apply to all
91  extensions, since some extensions fall outside of the realm of the standards
92  bodies.</li>
93
94  <li>A long-term support plan: increasingly large or complex extensions to
95  Clang need matching commitments to supporting them over time, including
96  improving their implementation and specification as Clang evolves. The
97  capacity of the contributor to make that commitment is as important as the
98  commitment itself.</li>
99
100  <li>A high-quality implementation: The implementation must fit well into
101  Clang's architecture, follow LLVM's coding conventions, and meet Clang's
102  quality standards, including diagnostics and complete AST
103  representations. This is particularly important for language extensions,
104  because users will learn how those extensions work through the behavior of the
105  compiler.</li>
106
107  <li>A test suite: Extensive testing is crucial to ensure that the language
108  extension is not broken by ongoing maintenance in Clang. The test suite
109  should be complete enough that another compiler vendor could conceivably
110  validate their implementation of the feature against it.</li>
111</ol>
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