www/get_involved.html - fp2-dev/platform/external/clang - Gitiles

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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,
 the <a href="get_started.html#ccc"><code>ccc</code></a> script in clang's
 <tt>utils</tt> folder 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="get_started.html#ccc"><code>ccc</code></a> might help you.  Once it
 compiles it should run.  If not, that's a bug :)</li>

 <li><b>Debug Info Generation</b>: -emit-llvm doesn't fully support emission
 of <a href="http://llvm.org/docs/SourceLevelDebugging.html">LLVM debug info</a>
 (which the code generator turns into DWARF).  The missing pieces are pretty
 minor at this point.</li>

 <li><b>Overflow detection</b>: an interesting project would be to add a -ftrapv
 compilation mode that causes -emit-llvm to generate overflow tests for all
 signed integer arithmetic operators, and call abort if they overflow.  Overflow
 is undefined in C and hard for people to reason about.  LLVM IR also has
 intrinsics for generating arithmetic with overflow checks directly.</li>

 <li><b>Undefined behavior checking</b>: similar to adding -ftrapv, codegen could
 insert runtime checks for all sorts of different undefined behaviors, from
 reading uninitialized variables, buffer overflows, and many other things.  This
 checking would be expensive, but the optimizers could eliminate many of the
 checks in some cases, and it would be very interesting to test code in this mode
 for certain crowds of people.  Because the inserted code is coming from clang,
 the "abort" message could be very detailed about exactly what went wrong.</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>

 <li><b>Implement an tool to generate code documentation</b>: Clang's
 library-based design allows it to be used by a variety of tools that reason
 about source code. One great application of Clang would be to build an
 auto-documentation system like doxygen that generates code documentation from
 source code. The advantage of using Clang for such a tool is that the tool would
 use the same preprocessor/parser/ASTs as the compiler itself, giving it a very
 rich understanding of the code.</li>

 <li><b>Use clang libraries to implement better versions of existing tools</b>:
 Clang is built as a set of libraries, which means that it is possible to
 implement capabilities similar to other source language tools, improving them
 in various ways.  Two examples are <a href="http://distcc.samba.org/">distcc</a>
 and the <a href="http://delta.tigris.org/">delta testcase reduction tool</a>.
 The former can be improved to scale better and be more efficient.  The later
 could also be faster and more efficient at reducing C-family programs if built
 on the clang preprocessor.</li>

 <li><b>Use clang libraries to extend Ragel with a JIT</b>: <a
 href="http://research.cs.queensu.ca/~thurston/ragel/">Ragel</a> is a state
 machine compiler that lets you embed C code into state machines and generate
 C code.  It would be relatively easy to turn this into a JIT compiler using
 LLVM.</li>

 <li><b>Self-testing using clang</b>: There are several neat ways to
 improve the quality of clang by self-testing. Some examples:
 <ul>
   <li>Improve the reliability of AST printing and serialization by
   ensuring that the AST produced by clang on an input doesn't change
   when it is reparsed or unserialized.

   <li>Improve parser reliability and error generation by automatically
   or randomly changing the input checking that clang doesn't crash and
   that it doesn't generate excessive errors for small input
   changes. Manipulating the input at both the text and token levels is
   likely to produce interesting test cases.
 </ul>
 </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>

 </div>
 </body>
 </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=ISO-8859-1" />
	<title>Clang - Get Involved</title>
	<link type="text/css" rel="stylesheet" href="menu.css" />
	<link type="text/css" rel="stylesheet" href="content.css" />
	</head>
	<body>

	<!--#include virtual="menu.html.incl"-->

	<div id="content">

	<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,
	the <a href="get_started.html#ccc"><code>ccc</code></a> script in clang's
	<tt>utils</tt> folder 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="get_started.html#ccc"><code>ccc</code></a> might help you. Once it
	compiles it should run. If not, that's a bug :)</li>

	<li><b>Debug Info Generation</b>: -emit-llvm doesn't fully support emission
	of <a href="http://llvm.org/docs/SourceLevelDebugging.html">LLVM debug info</a>
	(which the code generator turns into DWARF). The missing pieces are pretty
	minor at this point.</li>

	<li><b>Overflow detection</b>: an interesting project would be to add a -ftrapv
	compilation mode that causes -emit-llvm to generate overflow tests for all
	signed integer arithmetic operators, and call abort if they overflow. Overflow
	is undefined in C and hard for people to reason about. LLVM IR also has
	intrinsics for generating arithmetic with overflow checks directly.</li>

	<li><b>Undefined behavior checking</b>: similar to adding -ftrapv, codegen could
	insert runtime checks for all sorts of different undefined behaviors, from
	reading uninitialized variables, buffer overflows, and many other things. This
	checking would be expensive, but the optimizers could eliminate many of the
	checks in some cases, and it would be very interesting to test code in this mode
	for certain crowds of people. Because the inserted code is coming from clang,
	the "abort" message could be very detailed about exactly what went wrong.</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>

	<li><b>Implement an tool to generate code documentation</b>: Clang's
	library-based design allows it to be used by a variety of tools that reason
	about source code. One great application of Clang would be to build an
	auto-documentation system like doxygen that generates code documentation from
	source code. The advantage of using Clang for such a tool is that the tool would
	use the same preprocessor/parser/ASTs as the compiler itself, giving it a very
	rich understanding of the code.</li>

	<li><b>Use clang libraries to implement better versions of existing tools</b>:
	Clang is built as a set of libraries, which means that it is possible to
	implement capabilities similar to other source language tools, improving them
	in various ways. Two examples are <a href="http://distcc.samba.org/">distcc</a>
	and the <a href="http://delta.tigris.org/">delta testcase reduction tool</a>.
	The former can be improved to scale better and be more efficient. The later
	could also be faster and more efficient at reducing C-family programs if built
	on the clang preprocessor.</li>

	<li><b>Use clang libraries to extend Ragel with a JIT</b>: <a
	href="http://research.cs.queensu.ca/~thurston/ragel/">Ragel</a> is a state
	machine compiler that lets you embed C code into state machines and generate
	C code. It would be relatively easy to turn this into a JIT compiler using
	LLVM.</li>

	<li><b>Self-testing using clang</b>: There are several neat ways to
	improve the quality of clang by self-testing. Some examples:
	<ul>
	<li>Improve the reliability of AST printing and serialization by
	ensuring that the AST produced by clang on an input doesn't change
	when it is reparsed or unserialized.

	<li>Improve parser reliability and error generation by automatically
	or randomly changing the input checking that clang doesn't crash and
	that it doesn't generate excessive errors for small input
	changes. Manipulating the input at both the text and token levels is
	likely to produce interesting test cases.
	</ul>
	</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>

	</div>
	</body>
	</html>