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  16 <h1>Open Clang Projects</h1>
  17
  18 <p>Here are a few tasks that are available for newcomers to work on, depending
  19 on what your interests are.  This list is provided to generate ideas, it is not
  20 intended to be comprehensive.  Please ask on cfe-dev for more specifics or to
  21 verify that one of these isn't already completed. :)</p>
  22
  23 <ul>
  24 <li><b>Undefined behavior checking</b>:
  25 Improve and extend the runtime checks for undefined behavior which CodeGen
  26 inserts for the various <tt>-fsanitize=</tt> modes. A lot of issues can already
  27 be caught, but there is more to do here.</li>
  28
  29 <li><b>Improve target support</b>: The current target interfaces are heavily
  30 stubbed out and need to be implemented fully.  See the FIXME's in TargetInfo.
  31 Additionally, the actual target implementations (instances of TargetInfoImpl)
  32 also need to be completed.</li>
  33
  34 <li><b>Implement an tool to generate code documentation</b>: Clang's
  35 library-based design allows it to be used by a variety of tools that reason
  36 about source code. One great application of Clang would be to build an
  37 auto-documentation system like doxygen that generates code documentation from
  38 source code. The advantage of using Clang for such a tool is that the tool would
  39 use the same preprocessor/parser/ASTs as the compiler itself, giving it a very
  40 rich understanding of the code. Clang is already able to read and understand
  41 doxygen markup, but cannot yet generate documentation from it.</li>
  42
  43 <li><b>Use clang libraries to implement better versions of existing tools</b>:
  44 Clang is built as a set of libraries, which means that it is possible to
  45 implement capabilities similar to other source language tools, improving them
  46 in various ways.  Three examples are <a
  47 href="https://github.com/distcc">distcc</a>, the <a
  48 href="http://delta.tigris.org/">delta testcase reduction tool</a>, and the
  49 "indent" source reformatting tool.
  50 distcc can be improved to scale better and be more efficient.  Delta could be
  51 faster and more efficient at reducing C-family programs if built on the clang
  52 preprocessor. The clang-based indent replacement,
  53 <a href="https://clang.llvm.org/docs/ClangFormat.html">clang-format</a>,
  54 could be taught to handle simple structural rules like those in <a
  55 href="https://llvm.org/docs/CodingStandards.html#use-early-exits-and-continue-to-simplify-code">the LLVM coding
  56 standards</a>.</li>
  57
  58 <li><b>Use clang libraries to extend Ragel with a JIT</b>: <a
  59 href="https://www.colm.net/open-source/ragel/">Ragel</a> is a state
  60 machine compiler that lets you embed C code into state machines and generate
  61 C code.  It would be relatively easy to turn this into a JIT compiler using
  62 LLVM.</li>
  63
  64 <li><b>Self-testing using clang</b>: There are several neat ways to
  65 improve the quality of clang by self-testing. Some examples:
  66 <ul>
  67   <li>Improve the reliability of AST printing and serialization by
  68   ensuring that the AST produced by clang on an input doesn't change
  69   when it is reparsed or unserialized.
  70
  71   <li>Improve parser reliability and error generation by automatically
  72   or randomly changing the input checking that clang doesn't crash and
  73   that it doesn't generate excessive errors for small input
  74   changes. Manipulating the input at both the text and token levels is
  75   likely to produce interesting test cases.
  76 </ul>
  77 </li>
  78
  79 <li><b>Continue work on C++1y support</b>:
  80   C++98 and C++11 are feature-complete, but there are still several C++1y features to
  81   implement.  Please see the <a href="cxx_status.html">C++ status report
  82   page</a> to find out what is missing.</li>
  83
  84 <li><b>StringRef'ize APIs</b>: A thankless but incredibly useful project is
  85 StringRef'izing (converting to use <tt>llvm::StringRef</tt> instead of <tt>const
  86 char *</tt> or <tt>std::string</tt>) various clang interfaces. This generally
  87 simplifies the code and makes it more efficient.</li>
  88
  89 <li><b>Universal Driver</b>: Clang is inherently a cross compiler. We would like
  90 to define a new model for cross compilation which provides a great user
  91 experience -- it should be easy to cross compile applications, install support
  92 for new architectures, access different compilers and tools, and be consistent
  93 across different platforms. See the <a href="UniversalDriver.html">Universal
  94 Driver</a> web page for more information.</li>
  95
  96 <li><b>XML Representation of ASTs</b>: Clang maintains a rich Abstract Syntax Tree that describes the program. Clang could emit an XML document that describes the program, which others tools could consume rather than being tied directly to the Clang binary.The XML representation needs to meet several requirements:
  97   <ul>
  98     <li><i>General</i>, so that it's able to represent C/C++/Objective-C abstractly, and isn't tied to the specific internal ASTs that Clang uses.</li>
  99     <li><i>Documented</i>, with appropriate Schema against which the output of Clang's XML formatter can be verified.</li>
 100     <li><i>Stable</i> across Clang versions.</li>
 101   </ul></li>
 102
 103 <li><b>Configuration Manager</b>: Clang/LLVM works on a large number of
 104 architectures and operating systems and can cross-compile to a similarly large
 105 number of configurations, but the pitfalls of choosing the command-line
 106 options, making sure the right sub-architecture is chosen and that the correct
 107 optional elements of your particular system can be a pain.
 108
 109 <p>A tool that would investigate hosts and targets, and store the configuration
 110 in files that can later be used by Clang itself to avoid command-line options,
 111 especially the ones regarding which target options to use, would greatle alleviate
 112 this problem. A simple tool, with little or no dependency on LLVM itself, that
 113 will investigate a target architecture by probing hardware, software, libraries
 114 and compiling and executing code to identify all properties that would be relevant
 115 to command-line options (VFP, SSE, NEON, ARM vs. Thumb etc), triple settings etc.</p>
 116
 117 <p>The first stage is to build a CFLAGS for Clang that would produce code on the
 118 current Host to the identified Target.</p>
 119
 120 <p>The second stage would be to produce a configuration file (that can be used
 121 independently of the Host) so that Clang can read it and not need a gazillion
 122 of command-line options. Such file should be simple JSON / INI or anything that
 123 a text editor could change.</p>
 124 </ul>
 125
 126 <p>If you hit a bug with clang, it is very useful for us if you reduce the code
 127 that demonstrates the problem down to something small.  There are many ways to
 128 do this; ask on cfe-dev for advice.</p>
 129
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