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11 KiB
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
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<html>
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<META http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
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<title>Clang - Getting Started</title>
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<link type="text/css" rel="stylesheet" href="menu.css">
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<link type="text/css" rel="stylesheet" href="content.css">
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</head>
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<body>
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<!--#include virtual="menu.html.incl"-->
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<div id="content">
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<h1>Getting Started: Building and Running Clang</h1>
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<p>This page gives you the shortest path to checking out Clang and demos a few
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options. This should get you up and running with the minimum of muss and fuss.
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If you like what you see, please consider <a href="get_involved.html">getting
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involved</a> with the Clang community. If you run into problems, please file
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bugs in <a href="http://llvm.org/bugs/">LLVM Bugzilla</a>.</p>
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<h2 id="download">Release Clang Versions</h2>
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<p>Clang is released as part of regular LLVM releases. You can download the release versions from <a href="http://llvm.org/releases/">http://llvm.org/releases/</a>.</p>
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<p>Clang is also provided in all major BSD or GNU/Linux distributions as part of their respective packaging systems. From Xcode 4.2, Clang is the default compiler for Mac OS X.</p>
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<h2 id="build">Building Clang and Working with the Code</h2>
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<h3 id="buildNix">On Unix-like Systems</h3>
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<p>If you would like to check out and build Clang, the current procedure is as
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follows:</p>
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<ol>
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<li>Get the required tools.
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<ul>
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<li>See
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<a href="http://llvm.org/docs/GettingStarted.html#requirements">
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Getting Started with the LLVM System - Requirements</a>.</li>
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<li>Note also that Python is needed for running the test suite.
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Get it at: <a href="http://www.python.org/download">
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http://www.python.org/download</a></li>
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</ul>
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<li>Checkout LLVM:
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<ul>
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<li>Change directory to where you want the llvm directory placed.</li>
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<li><tt>svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm</tt></li>
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</ul>
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</li>
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<li>Checkout Clang:
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<ul>
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<li><tt>cd llvm/tools</tt></li>
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<li><tt>svn co http://llvm.org/svn/llvm-project/cfe/trunk clang</tt></li>
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<li><tt>cd ../..</tt></li>
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</ul>
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</li>
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<li>Checkout extra Clang Tools: (optional)
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<ul>
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<li><tt>cd llvm/tools/clang/tools</tt></li>
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<li><tt>svn co http://llvm.org/svn/llvm-project/clang-tools-extra/trunk
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extra</tt></li>
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<li><tt>cd ../../../..</tt></li>
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</ul>
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</li>
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<li>Checkout Compiler-RT:
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<ul>
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<li><tt>cd llvm/projects</tt></li>
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<li><tt>svn co http://llvm.org/svn/llvm-project/compiler-rt/trunk
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compiler-rt</tt></li>
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<li><tt>cd ../..</tt></li>
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</ul>
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</li>
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<li>Build LLVM and Clang:
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<ul>
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<li><tt>mkdir build</tt> (for building without polluting the source dir)
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</li>
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<li><tt>cd build</tt></li>
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<li><tt>../llvm/configure</tt></li>
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<li><tt>make</tt></li>
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<li>This builds both LLVM and Clang for debug mode.</li>
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<li>Note: For subsequent Clang development, you can just do make at the
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clang directory level.</li>
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<li>It is also possible to use CMake instead of the makefiles. With CMake
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it is possible to generate project files for several IDEs: Xcode, Eclipse
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CDT4, CodeBlocks, Qt-Creator (use the CodeBlocks generator), KDevelop3.</li>
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</ul>
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</li>
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<li>If you intend to use Clang's C++ support, you may need to tell it how
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to find your C++ standard library headers. In general, Clang will detect
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the best version of libstdc++ headers available and use them - it will
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look both for system installations of libstdc++ as well as installations
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adjacent to Clang itself. If your configuration fits neither of these
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scenarios, you can use the <tt>--with-gcc-toolchain</tt> configure option
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to tell Clang where the gcc containing the desired libstdc++ is installed.
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</li>
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<li>Try it out (assuming you add llvm/Debug+Asserts/bin to your path):
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<ul>
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<li><tt>clang --help</tt></li>
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<li><tt>clang file.c -fsyntax-only</tt> (check for correctness)</li>
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<li><tt>clang file.c -S -emit-llvm -o -</tt> (print out unoptimized llvm code)</li>
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<li><tt>clang file.c -S -emit-llvm -o - -O3</tt></li>
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<li><tt>clang file.c -S -O3 -o -</tt> (output native machine code)</li>
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</ul>
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</li>
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</ol>
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<p>Note that the C front-end uses LLVM, but does not depend on llvm-gcc. If you
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encounter problems with building Clang, make sure you have the latest SVN
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version of LLVM. LLVM contains support libraries for Clang that will be updated
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as well as development on Clang progresses.</p>
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<h3>Simultaneously Building Clang and LLVM:</h3>
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<p>Once you have checked out Clang into the llvm source tree it will build along
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with the rest of <tt>llvm</tt>. To build all of LLVM and Clang together all at
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once simply run <tt>make</tt> from the root LLVM directory.</p>
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<p><em>Note:</em> Observe that Clang is technically part of a separate
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Subversion repository. As mentioned above, the latest Clang sources are tied to
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the latest sources in the LLVM tree. You can update your toplevel LLVM project
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and all (possibly unrelated) projects inside it with <tt><b>make
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update</b></tt>. This will run <tt>svn update</tt> on all subdirectories related
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to subversion. </p>
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<h3 id="buildWindows">Using Visual Studio</h3>
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<p>The following details setting up for and building Clang on Windows using
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Visual Studio:</p>
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<ol>
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<li>Get the required tools:
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<ul>
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<li><b>Subversion</b>. Source code control program. Get it from:
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<a href="http://subversion.tigris.org/getting.html">
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http://subversion.tigris.org/getting.html</a></li>
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<li><b>CMake</b>. This is used for generating Visual Studio solution and
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project files. Get it from:
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<a href="http://www.cmake.org/cmake/resources/software.html">
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http://www.cmake.org/cmake/resources/software.html</a></li>
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<li><b>Visual Studio 2012 or later</b></li>
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<li><b>Python</b>. This is needed only if you will be running the tests
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(which is essential, if you will be developing for clang).
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Get it from:
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<a href="http://www.python.org/download/">
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http://www.python.org/download/</a></li>
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<li><b>GnuWin32 tools</b>
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These are also necessary for running the tests.
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(Note that the grep from MSYS or Cygwin doesn't work with the tests
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because of embedded double-quotes in the search strings. The GNU
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grep does work in this case.)
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Get them from <a href="http://getgnuwin32.sourceforge.net/">
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http://getgnuwin32.sourceforge.net/</a>.</li>
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</ul>
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</li>
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<li>Checkout LLVM:
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<ul>
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<li><tt>svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm</tt></li>
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</ul>
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</li>
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<li>Checkout Clang:
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<ul>
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<li><tt>cd llvm\tools</tt>
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<li><tt>svn co http://llvm.org/svn/llvm-project/cfe/trunk clang</tt></li>
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</ul>
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</li>
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<li>Run CMake to generate the Visual Studio solution and project files:
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<ul>
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<li><tt>cd ..\..</tt> (back to where you started)</li>
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<li><tt>mkdir build</tt> (for building without polluting the source dir)</li>
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<li><tt>cd build</tt></li>
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<li>If you are using Visual Studio 2012: <tt>cmake -G "Visual Studio 11" ..\llvm</tt></li>
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<li>See the <a href="http://www.llvm.org/docs/CMake.html">LLVM CMake guide</a> for
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more information on other configuration options for CMake.</li>
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<li>The above, if successful, will have created an LLVM.sln file in the
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<tt>build</tt> directory.
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</ul>
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</li>
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<li>Build Clang:
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<ul>
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<li>Open LLVM.sln in Visual Studio.</li>
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<li>Build the "clang" project for just the compiler driver and front end, or
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the "ALL_BUILD" project to build everything, including tools.</li>
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</ul>
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</li>
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<li>Try it out (assuming you added llvm/debug/bin to your path). (See the
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running examples from above.)</li>
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<li>See <a href="hacking.html#testingWindows">
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Hacking on clang - Testing using Visual Studio on Windows</a> for information
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on running regression tests on Windows.</li>
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</ol>
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<p>Note that once you have checked out both llvm and clang, to synchronize
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to the latest code base, use the <tt>svn update</tt> command in both the
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llvm and llvm\tools\clang directories, as they are separate repositories.</p>
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<h2 id="driver">Clang Compiler Driver (Drop-in Substitute for GCC)</h2>
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<p>The <tt>clang</tt> tool is the compiler driver and front-end, which is
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designed to be a drop-in replacement for the <tt>gcc</tt> command. Here are
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some examples of how to use the high-level driver:
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</p>
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<pre class="code">
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$ <b>cat t.c</b>
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#include <stdio.h>
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int main(int argc, char **argv) { printf("hello world\n"); }
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$ <b>clang t.c</b>
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$ <b>./a.out</b>
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hello world
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</pre>
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<p>The 'clang' driver is designed to work as closely to GCC as possible to
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maximize portability. The only major difference between the two is that
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Clang defaults to gnu99 mode while GCC defaults to gnu89 mode. If you see
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weird link-time errors relating to inline functions, try passing -std=gnu89
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to clang.</p>
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<h2>Examples of using Clang</h2>
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<!-- Thanks to
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http://shiflett.org/blog/2006/oct/formatting-and-highlighting-php-code-listings
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Site suggested using pre in CSS, but doesn't work in IE, so went for the <pre>
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tag. -->
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<pre class="code">
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$ <b>cat ~/t.c</b>
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typedef float V __attribute__((vector_size(16)));
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V foo(V a, V b) { return a+b*a; }
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</pre>
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<h3>Preprocessing:</h3>
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<pre class="code">
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$ <b>clang ~/t.c -E</b>
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# 1 "/Users/sabre/t.c" 1
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typedef float V __attribute__((vector_size(16)));
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V foo(V a, V b) { return a+b*a; }
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</pre>
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<h3>Type checking:</h3>
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<pre class="code">
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$ <b>clang -fsyntax-only ~/t.c</b>
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</pre>
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<h3>GCC options:</h3>
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<pre class="code">
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$ <b>clang -fsyntax-only ~/t.c -pedantic</b>
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/Users/sabre/t.c:2:17: <span style="color:magenta">warning:</span> extension used
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<span style="color:darkgreen">typedef float V __attribute__((vector_size(16)));</span>
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<span style="color:blue"> ^</span>
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1 diagnostic generated.
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</pre>
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<h3>Pretty printing from the AST:</h3>
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<p>Note, the <tt>-cc1</tt> argument indicates the compiler front-end, and
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not the driver, should be run. The compiler front-end has several additional
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Clang specific features which are not exposed through the GCC compatible driver
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interface.</p>
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<pre class="code">
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$ <b>clang -cc1 ~/t.c -ast-print</b>
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typedef float V __attribute__(( vector_size(16) ));
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V foo(V a, V b) {
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return a + b * a;
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}
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</pre>
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<h3>Code generation with LLVM:</h3>
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<pre class="code">
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$ <b>clang ~/t.c -S -emit-llvm -o -</b>
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define <4 x float> @foo(<4 x float> %a, <4 x float> %b) {
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entry:
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%mul = mul <4 x float> %b, %a
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%add = add <4 x float> %mul, %a
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ret <4 x float> %add
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}
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$ <b>clang -fomit-frame-pointer -O3 -S -o - t.c</b> <i># On x86_64</i>
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...
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_foo:
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Leh_func_begin1:
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mulps %xmm0, %xmm1
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addps %xmm1, %xmm0
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ret
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Leh_func_end1:
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</pre>
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</div>
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</body>
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</html>
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