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<h1>Getting Involved with the Clang Project</h1>

<p>Once you have <a href="get_started.html">checked out and built</a> clang and
played around with it, you might be wondering what you can do to make it better
and contribute to its development.  Alternatively, maybe you just want to follow
the development of the project to see it progress.
</p>

<h2>Follow what's going on</h2>

<p>Clang is a subproject of the <a href="http://llvm.org">LLVM Project</a>, but
has its own mailing lists because the communities have people with different
interests.  The two clang lists are:</p>

<ul>
<li><a href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits">cfe-commits
</a> - This list is for patch submission/discussion.</li>

<li><a href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev">cfe-dev</a> - 
This list is for everything else clang related (questions and answers, bug
reports, etc).</li>

</ul>

<p>If you are interested in clang only, these two lists should be all
you need.  If you are interested in the LLVM optimizer and code generator,
please consider signing up for <a 
href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">llvmdev</a> and <a
href="http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits">llvm-commits</a>
as well.</p>


<p>The best way to talk with other developers on the project is through the <a
href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev">cfe-dev mailing
list</a>.  The clang mailing list is a very friendly place and we welcome
newcomers.  In addition to the cfe-dev list, a significant amount of design
discussion takes place on the <a 
href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits">cfe-commits mailing
list</a>.  All of these lists have archives, so you can browse through previous
discussions or follow the list development on the web if you prefer.</p>


<h2>Open Projects</h2>

<p>Here are a few tasks that are available for newcomers to work on, depending
on what your interests are.  This list is provided to generate ideas, it is not
intended to be comprehensive.  Please ask on cfe-dev for more specifics or to
verify that one of these isn't already completed. :)</p>

<ul>
<li><b>Compile your favorite C/ObjC project with "clang -fsyntax-only"</b>:
the clang type checker and verifier is quite close to complete (but not bug
free!) for C and Objective C.  We appreciate all reports of code that is
rejected by the front-end, and if you notice invalid code that is not rejected
by clang, that is also very important to us.  For make-based projects,
<a href="http://lists.cs.uiuc.edu/pipermail/cfe-dev/2007-December/000613.html">
the script attached to this post</a> might help to get you started.</li>

<li><b>Compile your favorite C project with "clang -emit-llvm"</b>:
The clang to LLVM converter is getting more mature, so you may be able to
compile it.  If not, please let us know.  Again,
<a href="http://lists.cs.uiuc.edu/pipermail/cfe-dev/2007-December/000613.html">
the attachment to this post</a> might help you.  Once it compiles it should
run.  If not, that's a bug :)</li>

<li><b>Work on code generation for Objective C</b>: -emit-llvm support for
Objective C is basically nonexistent at the time of this writing, this is a
nice open project that can be tackled incrementally (one language feature at a
time).</li>

<li><b>Debug Info Generation</b>: -emit-llvm doesn't currently support emission
of <a href="http://llvm.org/docs/SourceLevelDebugging.html">LLVM debug info</a>
(which the code generator turns into DWARF).  Adding this should be
straight-forward if you follow the example of what llvm-gcc generates.</li>

<li><b>Continue work on C++ support</b>: Implementing all of C++ is a very big
job, but there are lots of little pieces that can be picked off and implemented.
See the <a href="cxx_status.html">C++ status report page</a> to find out what is
missing and what is already at least partially supported.</li>

<li><b>Improve target support</b>: The current target interfaces are heavily
stubbed out and need to be implemented fully.  See the FIXME's in TargetInfo.
Additionally, the actual target implementations (instances of TargetInfoImpl)
also need to be completed.  This includes defining builtin macros for linux
targets and other stuff like that.</li>

<li><b>Implement 'builtin' headers</b>: GCC provides a bunch of builtin headers,
such as stdbool.h, iso646.h, float.h, limits.h, etc.  It also provides a bunch
of target-specific headers like altivec.h and xmmintrin.h.  clang will
eventually need to provide its own copies of these (and there is a <a href=
"http://lists.cs.uiuc.edu/pipermail/cfe-dev/2007-December/000560.html">lot of 
improvement</a> that can be made to the GCC ones!) that are clean-room
implemented to avoid GPL taint.</li>

<li><b>Implement a clang 'libgcc'</b>: As with the headers, clang (or a another
related subproject of llvm) will need to implement the features that libgcc
provides. libgcc provides a bunch of routines the code generator uses for
"fallback" when the chip doesn't support some operation (e.g. 64-bit divide on
a 32-bit chip).  It also provides software floating point support and many other
things.  I don't think that there is a specific licensing reason to reimplement
libgcc, but there is a lot of room for improvement in it in many 
dimensions.</li>

</ul>

<p>If you hit a bug with clang, it is very useful for us if you reduce the code
that demonstrates the problem down to something small.  There are many ways to
do this; ask on cfe-dev for advice.</p>

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