open_projects.html - OpenGrok cross reference for /external/clang/www/analyzer/open_projects.html

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16<h1>Open Projects</h1>
17
18This 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.
24
25<ul>
26 <li>Core Analyzer Infrastructure
27 <ul>
28 <li>Explicitly model standard library functions with <tt>BodyFarm</tt>.
29 <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 (Difficulty: Easy, ongoing)
35 </li>
36
37 <li>Handle floating-point values.
38 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 (Difficulty: Medium)
45 </li>
46
47 <li>Implement generalized loop execution modeling.
48 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 (Difficulty: Hard)
54 </li>
55
56 <li>Enhance CFG to model C++ temporaries properly.
57 There is an existing implementation of this, but it's not complete and
58 is disabled in the analyzer.
59 (Difficulty: Medium; current contact: Alex McCarthy)
60
61 <li>Enhance CFG to model exception-handling properly.
62 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 (Difficulty: Medium)
66
67 <li>Enhance CFG to model C++ <code>new</code> more precisely.
68 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 (Difficulty: Easy; current contact: Karthik Bhat)
74
75 <li>Enhance CFG to model C++ <code>delete</code> more precisely.
76 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 (Difficulty: Easy; current contact: Karthik Bhat)
82
83 <li>Implement a BitwiseConstraintManager to handle <a href="http://llvm.org/bugs/show_bug.cgi?id=3098">PR3098</a>.
84 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 (Difficulty: Medium)
88 </li>
89
90 <li>Track type info through casts more precisely.
91 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 (Difficulty: Medium)
96
97 <li>Design and implement alpha-renaming.
98 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 (Difficulty: Hard)
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 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. (Difficulty: Medium) 
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 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. (Difficulty: Medium)
122 </li>
123 </ul>
124 </li>
125
126 <li>Other Infrastructure
127 <ul>
128 <li>Rewrite <tt>scan-build</tt> (in Python).
129 (Difficulty: Easy)
130 </li>
131
132 <li>Do a better job interposing on a compilation.
133 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 (Difficulty: Medium-Hard)
139 </li>
140
141 <li>Create an <tt>analyzer_annotate</tt> attribute for the analyzer
142 annotations.
143 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. (Difficulty: Medium)
147 </li>
148 </ul>
149 </li>
150
151 <li>Enhanced Checks
152 <ul>
153 <li>Implement a production-ready StreamChecker.
154 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 (Difficulty: Easy)
161 </li>
162
163 <li>Extend Malloc checker with reasoning about custom allocator,
164 deallocator, and ownership-transfer functions.
165 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 (Difficulty: Easy)
169 </li>
170
171 <li>Implement a BitwiseMaskingChecker to handle <a href="http://llvm.org/bugs/show_bug.cgi?id=16615">PR16615</a>.
172 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>.
173 (Difficulty: Easy)
174 </li>
175
176 <li>Implement iterators invalidation checker.
177 (Difficulty: Easy)
178 </li>
179
180 <li>Write checkers which catch Copy and Paste errors.
181 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 (Difficulty: Medium-Hard; current contacts: Per Viberg and Daniel Fahlgren)
185 </li>
186 </ul>
187 </li>
188</ul>
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