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<h1>Open Projects</h1>

<p>This page lists several projects that would boost analyzer's usability and 
power. Most of the projects listed here are infrastructure-related so this list 
is an addition to the <a href="potential_checkers.html">potential checkers 
list</a>. If you are interested in tackling one of these, please send an email 
to the <a href=http://lists.llvm.org/mailman/listinfo/cfe-dev>cfe-dev
mailing list</a> to notify other members of the community.</p>

<ul>  
  <li>Core Analyzer Infrastructure
  <ul>
    <li>Explicitly model standard library functions with <tt>BodyFarm</tt>.
    <p><tt><a href="http://clang.llvm.org/doxygen/classclang_1_1BodyFarm.html">BodyFarm</a></tt> 
    allows the analyzer to explicitly model functions whose definitions are 
    not available during analysis. Modeling more of the widely used functions 
    (such as the members of <tt>std::string</tt>) will improve precision of the
    analysis. 
    <i>(Difficulty: Easy, ongoing)</i><p>
    </li>

    <li>Handle floating-point values.
    <p>Currently, the analyzer treats all floating-point values as unknown.
    However, we already have most of the infrastructure we need to handle
    floats: RangeConstraintManager. This would involve adding a new SVal kind
    for constant floats, generalizing the constraint manager to handle floats
    and integers equally, and auditing existing code to make sure it doesn't
    make untoward assumptions.
    <i> (Difficulty: Medium)</i></p>
    </li>
    
    <li>Implement generalized loop execution modeling.
    <p>Currently, the analyzer simply unrolls each loop <tt>N</tt> times. This 
    means that it will not execute any code after the loop if the loop is 
    guaranteed to execute more than <tt>N</tt> times. This results in lost 
    basic block coverage. We could continue exploring the path if we could 
    model a generic <tt>i</tt>-th iteration of a loop.
    <i> (Difficulty: Hard)</i></p>
    </li>

    <li>Enhance CFG to model C++ temporaries properly.
    <p>There is an existing implementation of this, but it's not complete and
    is disabled in the analyzer.
    <i>(Difficulty: Medium; current contact: Alex McCarthy)</i></p>    

    <li>Enhance CFG to model exception-handling properly.
    <p>Currently exceptions are treated as "black holes", and exception-handling
    control structures are poorly modeled (to be conservative). This could be
    much improved for both C++ and Objective-C exceptions.
    <i>(Difficulty: Medium)</i></p>    

    <li>Enhance CFG to model C++ <code>new</code> more precisely.
    <p>The current representation of <code>new</code> does not provide an easy
    way for the analyzer to model the call to a memory allocation function
    (<code>operator new</code>), then initialize the result with a constructor
    call. The problem is discussed at length in
    <a href="http://llvm.org/bugs/show_bug.cgi?id=12014">PR12014</a>.
    <i>(Difficulty: Easy; current contact: Karthik Bhat)</i></p>

    <li>Enhance CFG to model C++ <code>delete</code> more precisely.
    <p>Similarly, the representation of <code>delete</code> does not include
    the call to the destructor, followed by the call to the deallocation
    function (<code>operator delete</code>). One particular issue 
    (<tt>noreturn</tt> destructors) is discussed in
    <a href="http://llvm.org/bugs/show_bug.cgi?id=15599">PR15599</a>
    <i>(Difficulty: Easy; current contact: Karthik Bhat)</i></p>    

    <li>Implement a BitwiseConstraintManager to handle <a href="http://llvm.org/bugs/show_bug.cgi?id=3098">PR3098</a>.
    <p>Constraints on the bits of an integer are not easily representable as
    ranges. A bitwise constraint manager would model constraints such as "bit 32
    is known to be 1". This would help code that made use of bitmasks</code>.
    <i>(Difficulty: Medium)</i></p>
    </li>

    <li>Track type info through casts more precisely.
    <p>The DynamicTypePropagation checker is in charge of inferring a region's
    dynamic type based on what operations the code is performing. Casts are a
    rich source of type information that the analyzer currently ignores. They
    are tricky to get right, but might have very useful consequences.
    <i>(Difficulty: Medium)</i></p>    

    <li>Design and implement alpha-renaming.
    <p>Implement unifying two symbolic values along a path after they are 
    determined to be equal via comparison. This would allow us to reduce the 
    number of false positives and would be a building step to more advanced 
    analyses, such as summary-based interprocedural and cross-translation-unit 
    analysis. 
    <i>(Difficulty: Hard)</i></p>
    </li>    
  </ul>
  </li>

  <li>Bug Reporting 
  <ul>
    <li>Refactor path diagnostic generation in <a href="http://clang.llvm.org/doxygen/BugReporter_8cpp_source.html">BugReporter.cpp</a>.
    <p>It would be great to have more code reuse between "Minimal" and 
    "Extensive" PathDiagnostic generation algorithms. One idea is to create an 
    IR for representing path diagnostics, which would be later be used to 
    generate minimal or extensive report output. <i>(Difficulty: Medium)</i></p>
    </li>
  </ul>
  </li>

  <li>Other Infrastructure 
  <ul>
    <li>Rewrite <tt>scan-build</tt> (in Python).
    <p><i>(Difficulty: Easy)</i></p>
    </li>

    <li>Do a better job interposing on a compilation.
    <p>Currently, <tt>scan-build</tt> just sets the <tt>CC</tt> and <tt>CXX</tt>
    environment variables to its wrapper scripts, which then call into an
    underlying platform compiler. This is problematic for any project that
    doesn't exclusively use <tt>CC</tt> and <tt>CXX</tt> to control its
    compilers.
    <p><i>(Difficulty: Medium-Hard)</i></p>
    </li>

    <li>Create an <tt>analyzer_annotate</tt> attribute for the analyzer 
    annotations.
    <p>We would like to put all analyzer attributes behind a fence so that we 
    could add/remove them without worrying that compiler (not analyzer) users 
    depend on them. Design and implement such a generic analyzer attribute in 
    the compiler. <i>(Difficulty: Medium)</i></p>
    </li>
  </ul>
  </li>

  <li>Enhanced Checks
  <ul>
    <li>Implement a production-ready StreamChecker.
    <p>A SimpleStreamChecker has been presented in the Building a Checker in 24 
    Hours talk 
    (<a href="http://llvm.org/devmtg/2012-11/Zaks-Rose-Checker24Hours.pdf">slides</a>
    <a href="http://llvm.org/devmtg/2012-11/videos/Zaks-Rose-Checker24Hours.mp4">video</a>). 
    We need to implement a production version of the checker with richer set of 
    APIs and evaluate it by running on real codebases. 
    <i>(Difficulty: Easy)</i></p>
    </li>

    <li>Extend Malloc checker with reasoning about custom allocator, 
    deallocator, and ownership-transfer functions.
    <p>This would require extending the MallocPessimistic checker to reason 
    about annotated functions. It is strongly desired that one would rely on 
    the <tt>analyzer_annotate</tt> attribute, as described above. 
    <i>(Difficulty: Easy)</i></p>
    </li>

    <li>Implement a BitwiseMaskingChecker to handle <a href="http://llvm.org/bugs/show_bug.cgi?id=16615">PR16615</a>.
    <p>Symbolic expressions of the form <code>$sym &amp; CONSTANT</code> can range from 0 to <code>CONSTANT-</code>1 if CONSTANT is <code>2^n-1</code>, e.g. 0xFF (0b11111111), 0x7F (0b01111111), 0x3 (0b0011), 0xFFFF, etc. Even without handling general bitwise operations on symbols, we can at least bound the value of the resulting expression. Bonus points for handling masks followed by shifts, e.g. <code>($sym &amp; 0b1100) >> 2</code>.
    <i>(Difficulty: Easy)</i></p>
    </li>

    <li>Implement iterators invalidation checker.
    <p><i>(Difficulty: Easy)</i></p>
    </li>
    
    <li>Write checkers which catch Copy and Paste errors.
    <p>Take a look at the
    <a href="http://pages.cs.wisc.edu/~shanlu/paper/TSE-CPMiner.pdf">CP-Miner</a>
    paper for inspiration. 
    <i>(Difficulty: Medium-Hard; current contacts: Daniel Marjam&auml;ki and Daniel Fahlgren)</i></p>
    </li>  
  </ul>
  </li>
</ul>

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