clang/www/analyzer/index.html

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