1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" 2 "http://www.w3.org/TR/html4/strict.dtd"> 3<html> 4<head> 5 <title>Open Projects</title> 6 <link type="text/css" rel="stylesheet" href="menu.css"> 7 <link type="text/css" rel="stylesheet" href="content.css"> 8 <script type="text/javascript" src="scripts/menu.js"></script> 9</head> 10<body> 11 12<div id="page"> 13<!--#include virtual="menu.html.incl"--> 14<div id="content"> 15 16<h1>Open Projects</h1> 17 18<p>This page lists several projects that would boost analyzer's usability and 19power. Most of the projects listed here are infrastructure-related so this list 20is an addition to the <a href="potential_checkers.html">potential checkers 21list</a>. If you are interested in tackling one of these, please send an email 22to the <a href=http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev>cfe-dev 23mailing list</a> to notify other members of the community.</p> 24 25<ul> 26 <li>Core Analyzer Infrastructure 27 <ul> 28 <li>Explicitly model standard library functions with <tt>BodyFarm</tt>. 29 <p><tt><a href="http://clang.llvm.org/doxygen/classclang_1_1BodyFarm.html">BodyFarm</a></tt> 30 allows the analyzer to explicitly model functions whose definitions are 31 not available during analysis. Modeling more of the widely used functions 32 (such as the members of <tt>std::string</tt>) will improve precision of the 33 analysis. 34 <i>(Difficulty: Easy, ongoing)</i><p> 35 </li> 36 37 <li>Handle floating-point values. 38 <p>Currently, the analyzer treats all floating-point values as unknown. 39 However, we already have most of the infrastructure we need to handle 40 floats: RangeConstraintManager. This would involve adding a new SVal kind 41 for constant floats, generalizing the constraint manager to handle floats 42 and integers equally, and auditing existing code to make sure it doesn't 43 make untoward assumptions. 44 <i> (Difficulty: Medium)</i></p> 45 </li> 46 47 <li>Implement generalized loop execution modeling. 48 <p>Currently, the analyzer simply unrolls each loop <tt>N</tt> times. This 49 means that it will not execute any code after the loop if the loop is 50 guaranteed to execute more than <tt>N</tt> times. This results in lost 51 basic block coverage. We could continue exploring the path if we could 52 model a generic <tt>i</tt>-th iteration of a loop. 53 <i> (Difficulty: Hard)</i></p> 54 </li> 55 56 <li>Enhance CFG to model C++ temporaries properly. 57 <p>There is an existing implementation of this, but it's not complete and 58 is disabled in the analyzer. 59 <i>(Difficulty: Medium)</i></p> 60 61 <li>Enhance CFG to model exception-handling properly. 62 <p>Currently exceptions are treated as "black holes", and exception-handling 63 control structures are poorly modeled (to be conservative). This could be 64 much improved for both C++ and Objective-C exceptions. 65 <i>(Difficulty: Medium)</i></p> 66 67 <li>Enhance CFG to model C++ <code>new</code> more precisely. 68 <p>The current representation of <code>new</code> does not provide an easy 69 way for the analyzer to model the call to a memory allocation function 70 (<code>operator new</code>), then initialize the result with a constructor 71 call. The problem is discussed at length in 72 <a href="http://llvm.org/bugs/show_bug.cgi?id=12014">PR12014</a>. 73 <i>(Difficulty: Easy)</i></p> 74 75 <li>Enhance CFG to model C++ <code>delete</code> more precisely. 76 <p>Similarly, the representation of <code>delete</code> does not include 77 the call to the destructor, followed by the call to the deallocation 78 function (<code>operator delete</code>). One particular issue 79 (<tt>noreturn</tt> destructors) is discussed in 80 <a href="http://llvm.org/bugs/show_bug.cgi?id=15599">PR15599</a> 81 <i>(Difficulty: Easy)</i></p> 82 83 <li>Track type info through casts more precisely. 84 <p>The DynamicTypePropagation checker is in charge of inferring a region's 85 dynamic type based on what operations the code is performing. Casts are a 86 rich source of type information that the analyzer currently ignores. They 87 are tricky to get right, but might have very useful consequences. 88 <i>(Difficulty: Medium)</i></p> 89 90 <li>Design and implement alpha-renaming. 91 <p>Implement unifying two symbolic values along a path after they are 92 determined to be equal via comparison. This would allow us to reduce the 93 number of false positives and would be a building step to more advanced 94 analyses, such as summary-based interprocedural and cross-translation-unit 95 analysis. 96 <i>(Difficulty: Hard)</i></p> 97 </li> 98 </ul> 99 </li> 100 101 <li>Bug Reporting 102 <ul> 103 <li>Add support for displaying cross-file diagnostic paths in HTML output 104 (used by <tt>scan-build</tt>). 105 <p>Currently <tt>scan-build</tt> output does not display reports that span 106 multiple files. The main problem is that we do not have a good format to 107 display such paths in HTML output. <i>(Difficulty: Medium)</i> </p> 108 </li> 109 110 <li>Relate bugs to checkers / "bug types" 111 <p>We need to come up with an API which will relate bug reports 112 to the checkers that produce them and refactor the existing code to use the 113 new API. This would allow us to identify the checker from the bug report, 114 which paves the way for selective control of certain checks. 115 <i>(Difficulty: Easy-Medium)</i></p> 116 </li> 117 118 <li>Refactor path diagnostic generation in <a href="http://clang.llvm.org/doxygen/BugReporter_8cpp_source.html">BugReporter.cpp</a>. 119 <p>It would be great to have more code reuse between "Minimal" and 120 "Extensive" PathDiagnostic generation algorithms. One idea is to create an 121 IR for representing path diagnostics, which would be later be used to 122 generate minimal or extensive report output. <i>(Difficulty: Medium)</i></p> 123 </li> 124 </ul> 125 </li> 126 127 <li>Other Infrastructure 128 <ul> 129 <li>Rewrite <tt>scan-build</tt> (in Python). 130 <p><i>(Difficulty: Easy)</i></p> 131 </li> 132 133 <li>Do a better job interposing on a compilation. 134 <p>Currently, <tt>scan-build</tt> just sets the <tt>CC</tt> and <tt>CXX</tt> 135 environment variables to its wrapper scripts, which then call into an 136 underlying platform compiler. This is problematic for any project that 137 doesn't exclusively use <tt>CC</tt> and <tt>CXX</tt> to control its 138 compilers. 139 <p><i>(Difficulty: Medium-Hard)</i></p> 140 </li> 141 142 <li>Create an <tt>analyzer_annotate</tt> attribute for the analyzer 143 annotations. 144 <p>We would like to put all analyzer attributes behind a fence so that we 145 could add/remove them without worrying that compiler (not analyzer) users 146 depend on them. Design and implement such a generic analyzer attribute in 147 the compiler. <i>(Difficulty: Medium)</i></p> 148 </li> 149 </ul> 150 </li> 151 152 <li>Enhanced Checks 153 <ul> 154 <li>Implement a production-ready StreamChecker. 155 <p>A SimpleStreamChecker has been presented in the Building a Checker in 24 156 Hours talk 157 (<a href="http://llvm.org/devmtg/2012-11/Zaks-Rose-Checker24Hours.pdf">slides</a> 158 <a href="http://llvm.org/devmtg/2012-11/videos/Zaks-Rose-Checker24Hours.mp4">video</a>). 159 We need to implement a production version of the checker with richer set of 160 APIs and evaluate it by running on real codebases. 161 <i>(Difficulty: Easy)</i></p> 162 </li> 163 164 <li>Extend Malloc checker with reasoning about custom allocator, 165 deallocator, and ownership-transfer functions. 166 <p>This would require extending the MallocPessimistic checker to reason 167 about annotated functions. It is strongly desired that one would rely on 168 the <tt>analyzer_annotate</tt> attribute, as described above. 169 <i>(Difficulty: Easy)</i></p> 170 </li> 171 172 <li>Implement a BitwiseMaskingChecker to handle <a href="http://llvm.org/bugs/show_bug.cgi?id=16615">PR16615</a>. 173 <p>Symbolic expressions of the form <code>$sym & CONSTANT</code> can range from 0 to <code>CONSTANT-</code>1 if CONSTANT is <code>2^n-1</code>, e.g. 0xFF (0b11111111), 0x7F (0b01111111), 0x3 (0b0011), 0xFFFF, etc. Even without handling general bitwise operations on symbols, we can at least bound the value of the resulting expression. Bonus points for handling masks followed by shifts, e.g. <code>($sym & 0b1100) >> 2</code>. 174 <i>(Difficulty: Easy)</i></p> 175 </li> 176 177 <li>Implement iterators invalidation checker. 178 <p><i>(Difficulty: Easy)</i></p> 179 </li> 180 181 <li>Write checkers which catch Copy and Paste errors. 182 <p>Take a look at the 183 <a href="http://pages.cs.wisc.edu/~shanlu/paper/TSE-CPMiner.pdf">CP-Miner</a> 184 paper for inspiration. 185 <i>(Difficulty: Medium-Hard)</i></p> 186 </li> 187 </ul> 188 </li> 189</ul> 190 191</div> 192</div> 193</body> 194</html> 195 196