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:</li> 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>Checkout Clang:</li> 54 <ul> 55 <li><tt>cd llvm/tools</tt> 56 <li><tt>svn co http://llvm.org/svn/llvm-project/cfe/trunk clang</tt></li> 57 </ul> 58 <li>Build LLVM and Clang:</li> 59 <ul> 60 <li><tt>cd ../..</tt> (back to where you started)</li> 61 <li><tt>mkdir build</tt> (for building without polluting the source dir) 62 </li> 63 <li><tt>cd build</tt></li> 64 <li><tt>../llvm/configure</tt></li> 65 <li><tt>make</tt></li> 66 <li>This builds both LLVM and Clang for debug mode.</li> 67 <li>Note: For subsequent Clang development, you can just do make at the 68 clang directory level.</li> 69 </ul> 70 71 <p>It is also possible to use CMake instead of the makefiles. With CMake it 72 is also possible to generate project files for several IDEs: Eclipse CDT4, 73 CodeBlocks, Qt-Creator (use the CodeBlocks generator), KDevelop3.</p> 74 75 <li>If you intend to work on Clang C++ support, you may need to tell it how 76 to find your C++ standard library headers. If Clang cannot find your 77 system libstdc++ headers, please follow these instructions:</li> 78 <ul> 79 <li>'<tt>gcc -v -x c++ /dev/null -fsyntax-only</tt>' to get the 80 path.</li> 81 <li>Look for the comment "FIXME: temporary hack: 82 hard-coded paths" in <tt>clang/lib/Frontend/InitHeaderSearch.cpp</tt> and 83 change the lines below to include that path.</li> 84 </ul> 85 <li>Try it out (assuming you add llvm/Debug+Asserts/bin to your path):</li> 86 <ul> 87 <li><tt>clang --help</tt></li> 88 <li><tt>clang file.c -fsyntax-only</tt> (check for correctness)</li> 89 <li><tt>clang file.c -S -emit-llvm -o -</tt> (print out unoptimized llvm code)</li> 90 <li><tt>clang file.c -S -emit-llvm -o - -O3</tt></li> 91 <li><tt>clang file.c -S -O3 -o -</tt> (output native machine code)</li> 92 </ul> 93</ol> 94 95<p>Note that the C front-end uses LLVM, but does not depend on llvm-gcc. If you 96encounter problems with building Clang, make sure you have the latest SVN 97version of LLVM. LLVM contains support libraries for Clang that will be updated 98as well as development on Clang progresses.</p> 99 100<h3>Simultaneously Building Clang and LLVM:</h3> 101 102<p>Once you have checked out Clang into the llvm source tree it will build along 103with the rest of <tt>llvm</tt>. To build all of LLVM and Clang together all at 104once simply run <tt>make</tt> from the root LLVM directory.</p> 105 106<p><em>Note:</em> Observe that Clang is technically part of a separate 107Subversion repository. As mentioned above, the latest Clang sources are tied to 108the latest sources in the LLVM tree. You can update your toplevel LLVM project 109and all (possibly unrelated) projects inside it with <tt><b>make 110update</b></tt>. This will run <tt>svn update</tt> on all subdirectories related 111to subversion. </p> 112 113<h3 id="buildWindows">Using Visual Studio</h3> 114 115<p>The following details setting up for and building Clang on Windows using 116Visual Studio:</p> 117 118<ol> 119 <li>Get the required tools:</li> 120 <ul> 121 <li><b>Subversion</b>. Source code control program. Get it from: 122 <a href="http://subversion.tigris.org/getting.html"> 123 http://subversion.tigris.org/getting.html</a></li> 124 <li><b>cmake</b>. This is used for generating Visual Studio solution and 125 project files. Get it from: 126 <a href="http://www.cmake.org/cmake/resources/software.html"> 127 http://www.cmake.org/cmake/resources/software.html</a></li> 128 <li><b>Visual Studio 2005, 2008, or 2010</b></li> 129 <li><b>Python</b>. This is needed only if you will be running the tests 130 (which is essential, if you will be developing for clang). 131 Get it from: 132 <a href="http://www.python.org/download/"> 133 http://www.python.org/download/</a></li> 134 <li><b>GnuWin32 tools</b> 135 These are also necessary for running the tests. 136 (Note that the grep from MSYS or Cygwin doesn't work with the tests 137 because of embedded double-quotes in the search strings. The GNU 138 grep does work in this case.) 139 Get them from <a href="http://getgnuwin32.sourceforge.net/"> 140 http://getgnuwin32.sourceforge.net/</a>.</li> 141 </ul> 142 143 <li>Checkout LLVM:</li> 144 <ul> 145 <li><tt>svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm</tt></li> 146 </ul> 147 <li>Checkout Clang:</li> 148 <ul> 149 <li><tt>cd llvm\tools</tt> 150 <li><tt>svn co http://llvm.org/svn/llvm-project/cfe/trunk clang</tt></li> 151 </ul> 152 <li>Run cmake to generate the Visual Studio solution and project files:</li> 153 <ul> 154 <li><tt>cd ..\..</tt> (back to where you started)</li> 155 <li><tt>mkdir build</tt> (for building without polluting the source dir)</li> 156 <li><tt>cd build</tt></li> 157 <li>If you are using Visual Studio 2005: <tt>cmake -G "Visual Studio 8 2005" ..\llvm</tt></li> 158 <li>Or if you are using Visual Studio 2008: <tt>cmake -G "Visual Studio 9 2008" ..\llvm</tt></li> 159 <li>Or if you are using Visual Studio 2010: <tt>cmake -G "Visual Studio 10" ..\llvm</tt></li> 160 <li>By default, cmake will target LLVM to X86. If you want all targets 161 (needed if you want to run the LLVM tests), add the <tt>-DLLVM_TARGETS_TO_BUILD=all</tt> option to the 162 cmake command line. Or specify a target from the LLVM_TARGETS_TO_BUILD 163 definition in CMakeLists.txt.</li> 164 <li>See the <a href="http://www.llvm.org/docs/CMake.html">LLVM CMake guide</a> for 165 more information on other configuration options for cmake.</li> 166</li> 167 <li>The above, if successful, will have created an LLVM.sln file in the 168 llvm directory. 169 </ul> 170 <li>Build Clang:</li> 171 <ul> 172 <li>Open LLVM.sln in Visual Studio.</li> 173 <li>Build the "clang" project for just the compiler driver and front end, or 174 the "ALL_BUILD" project to build everything, including tools.</li> 175 </ul> 176 <li>Try it out (assuming you added llvm/debug/bin to your path). (See the 177 running examples from above.)</li> 178 <li>See <a href="hacking.html#testingWindows"> 179 Hacking on clang - Testing using Visual Studio on Windows</a> for information 180 on running regression tests on Windows.</li> 181</ol> 182 183<p>Note that once you have checked out both llvm and clang, to synchronize 184to the latest code base, use the <tt>svn update</tt> command in both the 185llvm and llvm\tools\clang directories, as they are separate repositories.</p> 186 187<a name="driver"><h2>Clang Compiler Driver (Drop-in Substitute for GCC)</h2></a> 188 189<p>The <tt>clang</tt> tool is the compiler driver and front-end, which is 190designed to be a drop-in replacement for the <tt>gcc</tt> command. Here are 191some examples of how to use the high-level driver: 192</p> 193 194<pre class="code"> 195$ <b>cat t.c</b> 196#include <stdio.h> 197int main(int argc, char **argv) { printf("hello world\n"); } 198$ <b>clang t.c</b> 199$ <b>./a.out</b> 200hello world 201</pre> 202 203<p>The 'clang' driver is designed to work as closely to GCC as possible to 204 maximize portability. The only major difference between the two is that 205 Clang defaults to gnu99 mode while GCC defaults to gnu89 mode. If you see 206 weird link-time errors relating to inline functions, try passing -std=gnu89 207 to clang.</p> 208 209<h2>Examples of using Clang</h2> 210 211<!-- Thanks to 212 http://shiflett.org/blog/2006/oct/formatting-and-highlighting-php-code-listings 213Site suggested using pre in CSS, but doesn't work in IE, so went for the <pre> 214tag. --> 215 216<pre class="code"> 217$ <b>cat ~/t.c</b> 218typedef float V __attribute__((vector_size(16))); 219V foo(V a, V b) { return a+b*a; } 220</pre> 221 222 223<h3>Preprocessing:</h3> 224 225<pre class="code"> 226$ <b>clang ~/t.c -E</b> 227# 1 "/Users/sabre/t.c" 1 228 229typedef float V __attribute__((vector_size(16))); 230 231V foo(V a, V b) { return a+b*a; } 232</pre> 233 234 235<h3>Type checking:</h3> 236 237<pre class="code"> 238$ <b>clang -fsyntax-only ~/t.c</b> 239</pre> 240 241 242<h3>GCC options:</h3> 243 244<pre class="code"> 245$ <b>clang -fsyntax-only ~/t.c -pedantic</b> 246/Users/sabre/t.c:2:17: warning: extension used 247typedef float V __attribute__((vector_size(16))); 248 ^ 2491 diagnostic generated. 250</pre> 251 252 253<h3>Pretty printing from the AST:</h3> 254 255<p>Note, the <tt>-cc1</tt> argument indicates the the compiler front-end, and 256not the driver, should be run. The compiler front-end has several additional 257Clang specific features which are not exposed through the GCC compatible driver 258interface.</p> 259 260<pre class="code"> 261$ <b>clang -cc1 ~/t.c -ast-print</b> 262typedef float V __attribute__(( vector_size(16) )); 263V foo(V a, V b) { 264 return a + b * a; 265} 266</pre> 267 268 269<h3>Code generation with LLVM:</h3> 270 271<pre class="code"> 272$ <b>clang ~/t.c -S -emit-llvm -o -</b> 273define <4 x float> @foo(<4 x float> %a, <4 x float> %b) { 274entry: 275 %mul = mul <4 x float> %b, %a 276 %add = add <4 x float> %mul, %a 277 ret <4 x float> %add 278} 279$ <b>clang -fomit-frame-pointer -O3 -S -o - t.c</b> <i># On x86_64</i> 280... 281_foo: 282Leh_func_begin1: 283 mulps %xmm0, %xmm1 284 addps %xmm1, %xmm0 285 ret 286Leh_func_end1: 287</pre> 288 289</div> 290</body> 291</html> 292