1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" 2 "http://www.w3.org/TR/html4/strict.dtd"> 3<html> 4<head> 5 <META http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> 6 <title>Clang - Getting Started</title> 7 <link type="text/css" rel="stylesheet" href="menu.css"> 8 <link type="text/css" rel="stylesheet" href="content.css"> 9</head> 10<body> 11 12<!--#include virtual="menu.html.incl"--> 13 14<div id="content"> 15 16<h1>Getting Started: Building and Running Clang</h1> 17 18<p>This page gives you the shortest path to checking out Clang and demos a few 19options. This should get you up and running with the minimum of muss and fuss. 20If you like what you see, please consider <a href="get_involved.html">getting 21involved</a> with the Clang community. If you run into problems, please file 22bugs in <a href="http://llvm.org/bugs/">LLVM Bugzilla</a>.</p> 23 24<h2 id="download">Release Clang Versions</h2> 25 26<p>Clang has been released as part of regular LLVM releases since LLVM 2.6. You 27can download the release versions 28from <a href="http://llvm.org/releases/">http://llvm.org/releases/</a>.</p> 29 30<h2 id="build">Building Clang and Working with the Code</h2> 31 32<h3 id="buildNix">On Unix-like Systems</h3> 33 34<p>If you would like to check out and build Clang, the current procedure is as 35follows:</p> 36 37<ol> 38 <li>Get the required tools. 39 <ul> 40 <li>See 41 <a href="http://llvm.org/docs/GettingStarted.html#requirements"> 42 Getting Started with the LLVM System - Requirements</a>.</li> 43 <li>Note also that Python is needed for running the test suite. 44 Get it at: <a href="http://www.python.org/download"> 45 http://www.python.org/download</a></li> 46 </ul> 47 48 <li>Checkout LLVM: 49 <ul> 50 <li>Change directory to where you want the llvm directory placed.</li> 51 <li><tt>svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm</tt></li> 52 </ul> 53 </li> 54 <li>Checkout Clang: 55 <ul> 56 <li><tt>cd llvm/tools</tt></li> 57 <li><tt>svn co http://llvm.org/svn/llvm-project/cfe/trunk clang</tt></li> 58 <li><tt>cd ../..</tt></li> 59 </ul> 60 </li> 61 <li>Checkout extra Clang Tools: (optional) 62 <ul> 63 <li><tt>cd llvm/tools/clang/tools</tt></li> 64 <li><tt>svn co http://llvm.org/svn/llvm-project/clang-tools-extra/trunk 65 extra</tt></li> 66 <li><tt>cd ../../../..</tt></li> 67 </ul> 68 </li> 69 <li>Checkout Compiler-RT: 70 <ul> 71 <li><tt>cd llvm/projects</tt></li> 72 <li><tt>svn co http://llvm.org/svn/llvm-project/compiler-rt/trunk 73 compiler-rt</tt></li> 74 <li><tt>cd ../..</tt></li> 75 </ul> 76 </li> 77 <li>Build LLVM and Clang: 78 <ul> 79 <li><tt>mkdir build</tt> (for building without polluting the source dir) 80 </li> 81 <li><tt>cd build</tt></li> 82 <li><tt>../llvm/configure</tt></li> 83 <li><tt>make</tt></li> 84 <li>This builds both LLVM and Clang for debug mode.</li> 85 <li>Note: For subsequent Clang development, you can just do make at the 86 clang directory level.</li> 87 <li>It is also possible to use CMake instead of the makefiles. With CMake 88 it is possible to generate project files for several IDEs: Xcode, Eclipse 89 CDT4, CodeBlocks, Qt-Creator (use the CodeBlocks generator), KDevelop3.</li> 90 </ul> 91 </li> 92 93 <li>If you intend to use Clang's C++ support, you may need to tell it how 94 to find your C++ standard library headers. In general, Clang will detect 95 the best version of libstdc++ headers available and use them - it will 96 look both for system installations of libstdc++ as well as installations 97 adjacent to Clang itself. If your configuration fits neither of these 98 scenarios, you can use the <tt>--with-gcc-toolchain</tt> configure option 99 to tell Clang where the gcc containing the desired libstdc++ is installed. 100 </li> 101 <li>Try it out (assuming you add llvm/Debug+Asserts/bin to your path): 102 <ul> 103 <li><tt>clang --help</tt></li> 104 <li><tt>clang file.c -fsyntax-only</tt> (check for correctness)</li> 105 <li><tt>clang file.c -S -emit-llvm -o -</tt> (print out unoptimized llvm code)</li> 106 <li><tt>clang file.c -S -emit-llvm -o - -O3</tt></li> 107 <li><tt>clang file.c -S -O3 -o -</tt> (output native machine code)</li> 108 </ul> 109 </li> 110</ol> 111 112<p>Note that the C front-end uses LLVM, but does not depend on llvm-gcc. If you 113encounter problems with building Clang, make sure you have the latest SVN 114version of LLVM. LLVM contains support libraries for Clang that will be updated 115as well as development on Clang progresses.</p> 116 117<h3>Simultaneously Building Clang and LLVM:</h3> 118 119<p>Once you have checked out Clang into the llvm source tree it will build along 120with the rest of <tt>llvm</tt>. To build all of LLVM and Clang together all at 121once simply run <tt>make</tt> from the root LLVM directory.</p> 122 123<p><em>Note:</em> Observe that Clang is technically part of a separate 124Subversion repository. As mentioned above, the latest Clang sources are tied to 125the latest sources in the LLVM tree. You can update your toplevel LLVM project 126and all (possibly unrelated) projects inside it with <tt><b>make 127update</b></tt>. This will run <tt>svn update</tt> on all subdirectories related 128to subversion. </p> 129 130<h3 id="buildWindows">Using Visual Studio</h3> 131 132<p>The following details setting up for and building Clang on Windows using 133Visual Studio:</p> 134 135<ol> 136 <li>Get the required tools: 137 <ul> 138 <li><b>Subversion</b>. Source code control program. Get it from: 139 <a href="http://subversion.tigris.org/getting.html"> 140 http://subversion.tigris.org/getting.html</a></li> 141 <li><b>CMake</b>. This is used for generating Visual Studio solution and 142 project files. Get it from: 143 <a href="http://www.cmake.org/cmake/resources/software.html"> 144 http://www.cmake.org/cmake/resources/software.html</a></li> 145 <li><b>Visual Studio 2008 or 2010</b></li> 146 <li><b>Python</b>. This is needed only if you will be running the tests 147 (which is essential, if you will be developing for clang). 148 Get it from: 149 <a href="http://www.python.org/download/"> 150 http://www.python.org/download/</a></li> 151 <li><b>GnuWin32 tools</b> 152 These are also necessary for running the tests. 153 (Note that the grep from MSYS or Cygwin doesn't work with the tests 154 because of embedded double-quotes in the search strings. The GNU 155 grep does work in this case.) 156 Get them from <a href="http://getgnuwin32.sourceforge.net/"> 157 http://getgnuwin32.sourceforge.net/</a>.</li> 158 </ul> 159 </li> 160 161 <li>Checkout LLVM: 162 <ul> 163 <li><tt>svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm</tt></li> 164 </ul> 165 </li> 166 <li>Checkout Clang: 167 <ul> 168 <li><tt>cd llvm\tools</tt> 169 <li><tt>svn co http://llvm.org/svn/llvm-project/cfe/trunk clang</tt></li> 170 </ul> 171 </li> 172 <li>Run CMake to generate the Visual Studio solution and project files: 173 <ul> 174 <li><tt>cd ..\..</tt> (back to where you started)</li> 175 <li><tt>mkdir build</tt> (for building without polluting the source dir)</li> 176 <li><tt>cd build</tt></li> 177 <li>If you are using Visual Studio 2008: <tt>cmake -G "Visual Studio 9 2008" ..\llvm</tt></li> 178 <li>Or if you are using Visual Studio 2010: <tt>cmake -G "Visual Studio 10" ..\llvm</tt></li> 179 <li>See the <a href="http://www.llvm.org/docs/CMake.html">LLVM CMake guide</a> for 180 more information on other configuration options for CMake.</li> 181 <li>The above, if successful, will have created an LLVM.sln file in the 182 <tt>build</tt> directory. 183 </ul> 184 </li> 185 <li>Build Clang: 186 <ul> 187 <li>Open LLVM.sln in Visual Studio.</li> 188 <li>Build the "clang" project for just the compiler driver and front end, or 189 the "ALL_BUILD" project to build everything, including tools.</li> 190 </ul> 191 </li> 192 <li>Try it out (assuming you added llvm/debug/bin to your path). (See the 193 running examples from above.)</li> 194 <li>See <a href="hacking.html#testingWindows"> 195 Hacking on clang - Testing using Visual Studio on Windows</a> for information 196 on running regression tests on Windows.</li> 197</ol> 198 199<p>Note that once you have checked out both llvm and clang, to synchronize 200to the latest code base, use the <tt>svn update</tt> command in both the 201llvm and llvm\tools\clang directories, as they are separate repositories.</p> 202 203<h2 id="driver">Clang Compiler Driver (Drop-in Substitute for GCC)</h2> 204 205<p>The <tt>clang</tt> tool is the compiler driver and front-end, which is 206designed to be a drop-in replacement for the <tt>gcc</tt> command. Here are 207some examples of how to use the high-level driver: 208</p> 209 210<pre class="code"> 211$ <b>cat t.c</b> 212#include <stdio.h> 213int main(int argc, char **argv) { printf("hello world\n"); } 214$ <b>clang t.c</b> 215$ <b>./a.out</b> 216hello world 217</pre> 218 219<p>The 'clang' driver is designed to work as closely to GCC as possible to 220 maximize portability. The only major difference between the two is that 221 Clang defaults to gnu99 mode while GCC defaults to gnu89 mode. If you see 222 weird link-time errors relating to inline functions, try passing -std=gnu89 223 to clang.</p> 224 225<h2>Examples of using Clang</h2> 226 227<!-- Thanks to 228 http://shiflett.org/blog/2006/oct/formatting-and-highlighting-php-code-listings 229Site suggested using pre in CSS, but doesn't work in IE, so went for the <pre> 230tag. --> 231 232<pre class="code"> 233$ <b>cat ~/t.c</b> 234typedef float V __attribute__((vector_size(16))); 235V foo(V a, V b) { return a+b*a; } 236</pre> 237 238 239<h3>Preprocessing:</h3> 240 241<pre class="code"> 242$ <b>clang ~/t.c -E</b> 243# 1 "/Users/sabre/t.c" 1 244 245typedef float V __attribute__((vector_size(16))); 246 247V foo(V a, V b) { return a+b*a; } 248</pre> 249 250 251<h3>Type checking:</h3> 252 253<pre class="code"> 254$ <b>clang -fsyntax-only ~/t.c</b> 255</pre> 256 257 258<h3>GCC options:</h3> 259 260<pre class="code"> 261$ <b>clang -fsyntax-only ~/t.c -pedantic</b> 262/Users/sabre/t.c:2:17: <span style="color:magenta">warning:</span> extension used 263<span style="color:darkgreen">typedef float V __attribute__((vector_size(16)));</span> 264<span style="color:blue"> ^</span> 2651 diagnostic generated. 266</pre> 267 268 269<h3>Pretty printing from the AST:</h3> 270 271<p>Note, the <tt>-cc1</tt> argument indicates the compiler front-end, and 272not the driver, should be run. The compiler front-end has several additional 273Clang specific features which are not exposed through the GCC compatible driver 274interface.</p> 275 276<pre class="code"> 277$ <b>clang -cc1 ~/t.c -ast-print</b> 278typedef float V __attribute__(( vector_size(16) )); 279V foo(V a, V b) { 280 return a + b * a; 281} 282</pre> 283 284 285<h3>Code generation with LLVM:</h3> 286 287<pre class="code"> 288$ <b>clang ~/t.c -S -emit-llvm -o -</b> 289define <4 x float> @foo(<4 x float> %a, <4 x float> %b) { 290entry: 291 %mul = mul <4 x float> %b, %a 292 %add = add <4 x float> %mul, %a 293 ret <4 x float> %add 294} 295$ <b>clang -fomit-frame-pointer -O3 -S -o - t.c</b> <i># On x86_64</i> 296... 297_foo: 298Leh_func_begin1: 299 mulps %xmm0, %xmm1 300 addps %xmm1, %xmm0 301 ret 302Leh_func_end1: 303</pre> 304 305</div> 306</body> 307</html> 308