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				15	<h1>Clang Static Analyzer</h1>
				16
				17	<p>The Clang Static Analyzer consists of both a source code analysis framework
				18	and a standalone tool that finds bugs in C and Objective-C programs. The
				19	standalone tool is invoked from the command-line, and is intended to run in
				20	tandem with a build of a project or code base.</p>
				21
				22	<p>Both are 100% open source and are part of the <a
				23	href="http://clang.llvm.org">Clang</a> project.</p>
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				87	<h2 style="padding:0px; margin:0px">Download</h2>
				88	<h3 style="margin-top:5px">Mac OS X</h3>
				89	<ul>
				90	<li>Latest build (Universal binary, 10.5+):
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				92	</li>
				93	<li><a href="/installation.html">Installation</a> and <a
				94	href="/scan-build.html">usage</a></li>
				95	</ul>
				96	<h3>Other Platforms</h3>
				97	<p>For other platforms, please follow the instructions for <a
				98	href="/installation#OtherPlatforms">building the analyzer</a> from
				99	source code.<p>
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				110	<h2 id="StaticAnalysis">What is Static Analysis?</h2>
				111
				112	<p>The term "static analysis" is conflated, but here we use it to mean
				113	a collection of algorithms and techniques used to analyze source code in order
				114	to automatically find bugs. The idea is similar in spirit to compiler warnings
				115	(which can be useful for finding coding errors) but to take that idea a step
				116	further and find bugs that are traditionally found using run-time debugging
				117	techniques such as testing.</p>
				118
				119	<p>Static analysis bug-finding tools have evolved over the last several decades
				120	from basic syntactic checkers to those that find deep bugs by reasoning about
				121	the semantics of code. The goal of the Clang Static Analyzer is to provide a
				122	industrial-quality static analysis framework for analyzing C and Objective-C
				123	programs that is freely available, extensible, and has a high quality of
				124	implementation.</p>
				125
				126	<h3 id="Clang">Part of Clang and LLVM</h3>
				127
				128	<p>As its name implies, the Clang Static Analyzer is built on top of <a
				129	href="http://clang.llvm.org">Clang</a> and <a href="http://llvm.org">LLVM</a>.
				130	Strictly speaking, the analyzer is part of Clang, as Clang consists of a set of
				131	reusable C++ libraries for building powerful source-level tools. The static
				132	analysis engine used by the Clang Static Analyzer is a Clang library, and has
				133	the capability to be reused in different contexts and by different clients.</p>
				134
				135	<h2>Important Points to Consider</h2>
				136
				137	<p>While we believe that the static analyzer is already very useful for finding
				138	bugs, we ask you to bear in mind a few points when using it.</p>
				139
				140	<h3>Work-in-Progress</h3>
				141
				142	<p>The analyzer is a continuous work-in-progress.
				143	There are many planned enhancements to improve both the precision and scope of
				144	its analysis algorithms as well as the kinds bugs it will find. While there are
				145	fundamental limitations to what static analysis can do, we have a long way to go
				146	before hitting that wall.</p>
				147
				148	<h3>Slower than Compilation</h3>
				149
				150	<p>Operationally, using static analysis to
				151	automatically find deep program bugs is about trading CPU time for the hardening
				152	of code. Because of the deep analysis performed by state-of-the-art static
				153	analysis tools, static analysis can be much slower than compilation.</p>
				154
				155	<p>While the Clang Static Analyzer is being designed to be as fast and
				156	light-weight as possible, please do not expect it to be as fast as compiling a
				157	program (even with optimizations enabled). Some of the algorithms needed to find
				158	bugs require in the worst case exponential time.</p>
				159
				160	<p>The Clang Static Analyzer runs in a reasonable amount of time by both
				161	bounding the amount of checking work it will do as well as using clever
				162	algorithms to reduce the amount of work it must do to find bugs.</p></li>
				163
				164	<h3>False Positives</h3>
				165
				166	<p>Static analysis is not perfect. It can falsely flag bugs in a program where
				167	the code behaves correctly. Because some code checks require more analysis
				168	precision than others, the frequency of false positives can vary widely between
				169	different checks. Our long-term goal is to have the analyzer have a low false
				170	positive rate for most code on all checks.</p>
				171
				172	<p>Please help us in this endeavor by <a href="filing_bugs.html">reporting false
				173	positives</a>. False positives cannot be addressed unless we know about
				174	them.</p>
				175
				176	<h3>More Checks</h3>
				177
				178	<p>Static analysis not magic; a static analyzer can only find bugs that it has
				179	been specifically engineered to find. If there are specific kinds of bugs you
				180	would like the Clang Static Analyzer to find, please feel free to file <a
				181	href="filing_bugs.html">feature requests</a> or contribute your own patches.</p>
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