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 19 power. Most of the projects listed here are infrastructure-related so this list 20 is an addition to the <a href="potential_checkers.html">potential checkers 21 list</a>. If you are interested in tackling one of these, please send an email 22 to the <a href=http://lists.llvm.org/mailman/listinfo/cfe-dev>cfe-dev 23 mailing 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; current contact: Alex McCarthy)</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; current contact: Karthik Bhat)</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; current contact: Karthik Bhat)</i></p> 82 83 <li>Implement a BitwiseConstraintManager to handle <a href="http://llvm.org/bugs/show_bug.cgi?id=3098">PR3098</a>. 84 <p>Constraints on the bits of an integer are not easily representable as 85 ranges. A bitwise constraint manager would model constraints such as "bit 32 86 is known to be 1". This would help code that made use of bitmasks</code>. 87 <i>(Difficulty: Medium)</i></p> 88 </li> 89 90 <li>Track type info through casts more precisely. 91 <p>The DynamicTypePropagation checker is in charge of inferring a region's 92 dynamic type based on what operations the code is performing. Casts are a 93 rich source of type information that the analyzer currently ignores. They 94 are tricky to get right, but might have very useful consequences. 95 <i>(Difficulty: Medium)</i></p> 96 97 <li>Design and implement alpha-renaming. 98 <p>Implement unifying two symbolic values along a path after they are 99 determined to be equal via comparison. This would allow us to reduce the 100 number of false positives and would be a building step to more advanced 101 analyses, such as summary-based interprocedural and cross-translation-unit 102 analysis. 103 <i>(Difficulty: Hard)</i></p> 104 </li> 105 </ul> 106 </li> 107 108 <li>Bug Reporting 109 <ul> 110 <li>Add support for displaying cross-file diagnostic paths in HTML output 111 (used by <tt>scan-build</tt>). 112 <p>Currently <tt>scan-build</tt> output does not display reports that span 113 multiple files. The main problem is that we do not have a good format to 114 display such paths in HTML output. <i>(Difficulty: Medium)</i> </p> 115 </li> 116 117 <li>Refactor path diagnostic generation in <a href="http://clang.llvm.org/doxygen/BugReporter_8cpp_source.html">BugReporter.cpp</a>. 118 <p>It would be great to have more code reuse between "Minimal" and 119 "Extensive" PathDiagnostic generation algorithms. One idea is to create an 120 IR for representing path diagnostics, which would be later be used to 121 generate minimal or extensive report output. <i>(Difficulty: Medium)</i></p> 122 </li> 123 </ul> 124 </li> 125 126 <li>Other Infrastructure 127 <ul> 128 <li>Rewrite <tt>scan-build</tt> (in Python). 129 <p><i>(Difficulty: Easy)</i></p> 130 </li> 131 132 <li>Do a better job interposing on a compilation. 133 <p>Currently, <tt>scan-build</tt> just sets the <tt>CC</tt> and <tt>CXX</tt> 134 environment variables to its wrapper scripts, which then call into an 135 underlying platform compiler. This is problematic for any project that 136 doesn't exclusively use <tt>CC</tt> and <tt>CXX</tt> to control its 137 compilers. 138 <p><i>(Difficulty: Medium-Hard)</i></p> 139 </li> 140 141 <li>Create an <tt>analyzer_annotate</tt> attribute for the analyzer 142 annotations. 143 <p>We would like to put all analyzer attributes behind a fence so that we 144 could add/remove them without worrying that compiler (not analyzer) users 145 depend on them. Design and implement such a generic analyzer attribute in 146 the compiler. <i>(Difficulty: Medium)</i></p> 147 </li> 148 </ul> 149 </li> 150 151 <li>Enhanced Checks 152 <ul> 153 <li>Implement a production-ready StreamChecker. 154 <p>A SimpleStreamChecker has been presented in the Building a Checker in 24 155 Hours talk 156 (<a href="http://llvm.org/devmtg/2012-11/Zaks-Rose-Checker24Hours.pdf">slides</a> 157 <a href="http://llvm.org/devmtg/2012-11/videos/Zaks-Rose-Checker24Hours.mp4">video</a>). 158 We need to implement a production version of the checker with richer set of 159 APIs and evaluate it by running on real codebases. 160 <i>(Difficulty: Easy)</i></p> 161 </li> 162 163 <li>Extend Malloc checker with reasoning about custom allocator, 164 deallocator, and ownership-transfer functions. 165 <p>This would require extending the MallocPessimistic checker to reason 166 about annotated functions. It is strongly desired that one would rely on 167 the <tt>analyzer_annotate</tt> attribute, as described above. 168 <i>(Difficulty: Easy)</i></p> 169 </li> 170 171 <li>Implement a BitwiseMaskingChecker to handle <a href="http://llvm.org/bugs/show_bug.cgi?id=16615">PR16615</a>. 172 <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>. 173 <i>(Difficulty: Easy)</i></p> 174 </li> 175 176 <li>Implement iterators invalidation checker. 177 <p><i>(Difficulty: Easy)</i></p> 178 </li> 179 180 <li>Write checkers which catch Copy and Paste errors. 181 <p>Take a look at the 182 <a href="http://pages.cs.wisc.edu/~shanlu/paper/TSE-CPMiner.pdf">CP-Miner</a> 183 paper for inspiration. 184 <i>(Difficulty: Medium-Hard; current contacts: Daniel Marjamäki and Daniel Fahlgren)</i></p> 185 </li> 186 </ul> 187 </li> 188 </ul> 189 190 </div> 191 </div> 192 </body> 193 </html> 194 195
