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| 5 | <title>Clang Static Analyzer</title> |
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| 63 | <!--#include virtual="menu.html.incl"--> |
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| 64 | <div id="content"> |
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| 65 | |
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| 66 | |
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| 67 | <table style="margin-top:0px" width="100%" border="0" cellpadding="0px" cellspacing="0"> |
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| 68 | <tr><td> |
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| 69 | |
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| 70 | <h1>Clang Static Analyzer</h1> |
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| 71 | |
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| 72 | <p>The Clang Static Analyzer is a source code analysis tool that finds bugs in |
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| 73 | C, C++, and Objective-C programs.</p> |
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| 74 | |
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| 75 | <p>Currently it can be run either as a <a href="scan-build.html">standalone |
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| 76 | tool</a> or <a href="xcode.html">within Xcode</a>. The standalone tool is |
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| 77 | invoked from the command line, and is intended to be run in tandem with a build |
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| 78 | of a codebase.</p> |
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| 79 | |
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| 80 | <p>The analyzer is 100% open source and is part of the <a |
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| 81 | href="http://clang.llvm.org">Clang</a> project. Like the rest of Clang, the |
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| 82 | analyzer is implemented as a C++ library that can be used by other tools and |
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| 83 | applications.</p> |
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| 84 | |
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| 85 | <h2>Download</h2> |
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| 86 | |
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| 87 | <div style="padding:0px; font-size: 90%"> |
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| 88 | <b class="spiffy"> |
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| 94 | <div class="spiffyfg"> |
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| 95 | <div style="padding:15px"> |
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| 96 | <h3 style="margin:0px;padding:0px">Mac OS X</h3> |
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| 97 | <ul> |
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| 98 | <li>Latest build (10.8+):<br> |
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| 99 | <!--#include virtual="latest_checker.html.incl"--> |
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| 100 | </li> |
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| 101 | <li><a href="/release_notes.html">Release notes</a></li> |
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| 102 | <li>This build can be used both from the command line and from within Xcode</li> |
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| 103 | <li><a href="/installation.html">Installation</a> and <a href="/scan-build.html">usage</a></li> |
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| 104 | </ul> |
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| 105 | </div> |
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| 106 | </div> |
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| 114 | |
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| 122 | <div class="spiffyfg"> |
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| 123 | <div style="padding:15px"> |
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| 124 | <h3 style="margin:0px;padding:0px">Other Platforms</h3> |
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| 125 | <p>For other platforms, please follow the instructions for <a |
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| 126 | href="/installation#OtherPlatforms">building the analyzer</a> from |
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| 127 | source code.<p> |
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| 128 | </div> |
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| 129 | </div> |
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| 130 | <b class="spiffy"> |
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| 136 | </div> |
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| 137 | |
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| 138 | |
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| 139 | </td><td style="padding-left:10px"> |
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| 140 | <a href="images/analyzer_xcode.png"><img src="images/analyzer_xcode.png" width="450" alt="analyzer in xcode"></a> |
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| 141 | <div style="text-align:center"><b>Viewing static analyzer results in Xcode</b></div> |
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| 142 | <a href="images/analyzer_html.png"><img src="images/analyzer_html.png" width="450" alt="analyzer in browser"></a> |
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| 143 | <div style="text-align:center"><b>Viewing static analyzer results in a web browser</b></div> |
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| 144 | </td></tr></table> |
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| 145 | |
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| 146 | <h2 id="StaticAnalysis">What is Static Analysis?</h2> |
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| 147 | |
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| 148 | <p>The term "static analysis" is conflated, but here we use it to mean |
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| 149 | a collection of algorithms and techniques used to analyze source code in order |
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| 150 | to automatically find bugs. The idea is similar in spirit to compiler warnings |
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| 151 | (which can be useful for finding coding errors) but to take that idea a step |
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| 152 | further and find bugs that are traditionally found using run-time debugging |
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| 153 | techniques such as testing.</p> |
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| 154 | |
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| 155 | <p>Static analysis bug-finding tools have evolved over the last several decades |
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| 156 | from basic syntactic checkers to those that find deep bugs by reasoning about |
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| 157 | the semantics of code. The goal of the Clang Static Analyzer is to provide a |
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| 158 | industrial-quality static analysis framework for analyzing C, C++, and |
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| 159 | Objective-C programs that is freely available, extensible, and has a high quality of implementation.</p> |
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| 160 | |
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| 161 | <h3 id="Clang">Part of Clang and LLVM</h3> |
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| 162 | |
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| 163 | <p>As its name implies, the Clang Static Analyzer is built on top of <a |
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| 164 | href="http://clang.llvm.org">Clang</a> and <a href="http://llvm.org">LLVM</a>. |
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| 165 | Strictly speaking, the analyzer is part of Clang, as Clang consists of a set of |
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| 166 | reusable C++ libraries for building powerful source-level tools. The static |
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| 167 | analysis engine used by the Clang Static Analyzer is a Clang library, and has |
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| 168 | the capability to be reused in different contexts and by different clients.</p> |
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| 169 | |
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| 170 | <h2>Important Points to Consider</h2> |
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| 171 | |
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| 172 | <p>While we believe that the static analyzer is already very useful for finding |
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| 173 | bugs, we ask you to bear in mind a few points when using it.</p> |
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| 174 | |
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| 175 | <h3>Work-in-Progress</h3> |
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| 176 | |
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| 177 | <p>The analyzer is a continuous work-in-progress. There are many planned |
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| 178 | enhancements to improve both the precision and scope of its analysis algorithms |
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| 179 | as well as the kinds of bugs it will find. While there are fundamental |
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| 180 | limitations to what static analysis can do, we have a long way to go before |
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| 181 | hitting that wall.</p> |
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| 182 | |
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| 183 | <h3>Slower than Compilation</h3> |
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| 184 | |
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| 185 | <p>Operationally, using static analysis to |
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| 186 | automatically find deep program bugs is about trading CPU time for the hardening |
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| 187 | of code. Because of the deep analysis performed by state-of-the-art static |
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| 188 | analysis tools, static analysis can be much slower than compilation.</p> |
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| 189 | |
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| 190 | <p>While the Clang Static Analyzer is being designed to be as fast and |
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| 191 | light-weight as possible, please do not expect it to be as fast as compiling a |
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| 192 | program (even with optimizations enabled). Some of the algorithms needed to find |
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| 193 | bugs require in the worst case exponential time.</p> |
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| 194 | |
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| 195 | <p>The Clang Static Analyzer runs in a reasonable amount of time by both |
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| 196 | bounding the amount of checking work it will do as well as using clever |
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| 197 | algorithms to reduce the amount of work it must do to find bugs.</p> |
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| 198 | |
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| 199 | <h3>False Positives</h3> |
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| 200 | |
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| 201 | <p>Static analysis is not perfect. It can falsely flag bugs in a program where |
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| 202 | the code behaves correctly. Because some code checks require more analysis |
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| 203 | precision than others, the frequency of false positives can vary widely between |
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| 204 | different checks. Our long-term goal is to have the analyzer have a low false |
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| 205 | positive rate for most code on all checks.</p> |
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| 206 | |
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| 207 | <p>Please help us in this endeavor by <a href="filing_bugs.html">reporting false |
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| 208 | positives</a>. False positives cannot be addressed unless we know about |
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| 209 | them.</p> |
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| 210 | |
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| 211 | <h3>More Checks</h3> |
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| 212 | |
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| 213 | <p>Static analysis is not magic; a static analyzer can only find bugs that it |
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| 214 | has been specifically engineered to find. If there are specific kinds of bugs |
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| 215 | you would like the Clang Static Analyzer to find, please feel free to |
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| 216 | file <a href="filing_bugs.html">feature requests</a> or contribute your own |
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| 217 | patches.</p> |
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| 218 | |
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| 219 | </div> |
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| 220 | </div> |
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| 221 | </body> |
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| 222 | </html> |
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