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188 строки
6.4 KiB
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188 строки
6.4 KiB
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<title>Clang Static Analyzer</title>
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<h1>Clang Static Analyzer</h1>
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<p>The Clang Static Analyzer consists of both a source code analysis framework
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and a standalone tool that finds bugs in C and Objective-C programs. The
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standalone tool is invoked from the command-line, and is intended to run in
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tandem with a build of a project or code base.</p>
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<p>Both are 100% open source and are part of the <a
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href="http://clang.llvm.org">Clang</a> project.</p>
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<div style="padding:15px">
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<h2 style="padding:0px; margin:0px">Download</h2>
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<h3 style="margin-top:5px">Mac OS X</h3>
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<ul>
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<li>Latest build (Universal binary, 10.5+):
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<!--#include virtual="latest_checker.html.incl"-->
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</li>
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<li><a href="/installation.html">Installation</a> and <a
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href="/scan-build.html">usage</a></li>
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</ul>
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<h3>Other Platforms</h3>
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<p>For other platforms, please follow the instructions for <a
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href="/installation#OtherPlatforms">building the analyzer</a> from
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source code.<p>
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<h2 id="StaticAnalysis">What is Static Analysis?</h2>
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<p>The term "static analysis" is conflated, but here we use it to mean
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a collection of algorithms and techniques used to analyze source code in order
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to automatically find bugs. The idea is similar in spirit to compiler warnings
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(which can be useful for finding coding errors) but to take that idea a step
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further and find bugs that are traditionally found using run-time debugging
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techniques such as testing.</p>
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<p>Static analysis bug-finding tools have evolved over the last several decades
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from basic syntactic checkers to those that find deep bugs by reasoning about
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the semantics of code. The goal of the Clang Static Analyzer is to provide a
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industrial-quality static analysis framework for analyzing C and Objective-C
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programs that is freely available, extensible, and has a high quality of
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implementation.</p>
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<h3 id="Clang">Part of Clang and LLVM</h3>
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<p>As its name implies, the Clang Static Analyzer is built on top of <a
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href="http://clang.llvm.org">Clang</a> and <a href="http://llvm.org">LLVM</a>.
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Strictly speaking, the analyzer is part of Clang, as Clang consists of a set of
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reusable C++ libraries for building powerful source-level tools. The static
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analysis engine used by the Clang Static Analyzer is a Clang library, and has
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the capability to be reused in different contexts and by different clients.</p>
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<h2>Important Points to Consider</h2>
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<p>While we believe that the static analyzer is already very useful for finding
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bugs, we ask you to bear in mind a few points when using it.</p>
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<h3>Work-in-Progress</h3>
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<p>The analyzer is a continuous work-in-progress.
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There are many planned enhancements to improve both the precision and scope of
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its analysis algorithms as well as the kinds bugs it will find. While there are
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fundamental limitations to what static analysis can do, we have a long way to go
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before hitting that wall.</p>
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<h3>Slower than Compilation</h3>
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<p>Operationally, using static analysis to
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automatically find deep program bugs is about trading CPU time for the hardening
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of code. Because of the deep analysis performed by state-of-the-art static
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analysis tools, static analysis can be much slower than compilation.</p>
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<p>While the Clang Static Analyzer is being designed to be as fast and
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light-weight as possible, please do not expect it to be as fast as compiling a
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program (even with optimizations enabled). Some of the algorithms needed to find
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bugs require in the worst case exponential time.</p>
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<p>The Clang Static Analyzer runs in a reasonable amount of time by both
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bounding the amount of checking work it will do as well as using clever
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algorithms to reduce the amount of work it must do to find bugs.</p></li>
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<h3>False Positives</h3>
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<p>Static analysis is not perfect. It can falsely flag bugs in a program where
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the code behaves correctly. Because some code checks require more analysis
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precision than others, the frequency of false positives can vary widely between
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different checks. Our long-term goal is to have the analyzer have a low false
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positive rate for most code on all checks.</p>
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<p>Please help us in this endeavor by <a href="filing_bugs.html">reporting false
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positives</a>. False positives cannot be addressed unless we know about
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them.</p>
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<h3>More Checks</h3>
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<p>Static analysis is not magic; a static analyzer can only find bugs that it
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has been specifically engineered to find. If there are specific kinds of bugs
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you would like the Clang Static Analyzer to find, please feel free to
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file <a href="filing_bugs.html">feature requests</a> or contribute your own
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patches.</p>
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</div>
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