external/bsd/llvm/dist/clang/www/get_started.html

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  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
  19 options.  This should get you up and running with the minimum of muss and fuss.
  20 If you like what you see, please consider <a href="get_involved.html">getting
  21 involved</a> with the Clang community.  If you run into problems, please file
  22 bugs in <a href="http://llvm.org/bugs/">LLVM Bugzilla</a>.</p>
  23
  24 <h2 id="download">Release Clang Versions</h2>
  25
  26 <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>
  27 <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>
  28
  29 <h2 id="build">Building Clang and Working with the Code</h2>
  30
  31 <h3 id="buildNix">On Unix-like Systems</h3>
  32
  33 <p>If you would like to check out and build Clang, the current procedure is as
  34 follows:</p>
  35
  36 <ol>
  37   <li>Get the required tools.
  38   <ul>
  39     <li>See
  40       <a href="http://llvm.org/docs/GettingStarted.html#requirements">
  41       Getting Started with the LLVM System - Requirements</a>.</li>
  42     <li>Note also that Python is needed for running the test suite.
  43       Get it at: <a href="http://www.python.org/download">
  44       http://www.python.org/download</a></li>
  45   </ul>
  46
  47   <li>Checkout LLVM:
  48   <ul>
  49     <li>Change directory to where you want the llvm directory placed.</li>
  50     <li><tt>svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm</tt></li>
  51   </ul>
  52   </li>
  53   <li>Checkout Clang:
  54   <ul>
  55     <li><tt>cd llvm/tools</tt></li>
  56     <li><tt>svn co http://llvm.org/svn/llvm-project/cfe/trunk clang</tt></li>
  57     <li><tt>cd ../..</tt></li>
  58   </ul>
  59   </li>
  60   <li>Checkout extra Clang Tools: (optional)
  61   <ul>
  62     <li><tt>cd llvm/tools/clang/tools</tt></li>
  63     <li><tt>svn co http://llvm.org/svn/llvm-project/clang-tools-extra/trunk
  64         extra</tt></li>
  65     <li><tt>cd ../../../..</tt></li>
  66   </ul>
  67   </li>
  68   <li>Checkout Compiler-RT:
  69   <ul>
  70     <li><tt>cd llvm/projects</tt></li>
  71     <li><tt>svn co http://llvm.org/svn/llvm-project/compiler-rt/trunk
  72         compiler-rt</tt></li>
  73     <li><tt>cd ../..</tt></li>
  74   </ul>
  75   </li>
  76   <li>Build LLVM and Clang:
  77   <ul>
  78     <li><tt>mkdir build</tt> (for building without polluting the source dir)
  79     </li>
  80     <li><tt>cd build</tt></li>
  81     <li><tt>../llvm/configure</tt></li>
  82     <li><tt>make</tt></li>
  83     <li>This builds both LLVM and Clang for debug mode.</li>
  84     <li>Note: For subsequent Clang development, you can just do make at the
  85     clang directory level.</li>
  86     <li>It is also possible to use CMake instead of the makefiles. With CMake
  87     it is possible to generate project files for several IDEs: Xcode, Eclipse
  88     CDT4, CodeBlocks, Qt-Creator (use the CodeBlocks generator), KDevelop3.</li>
  89   </ul>
  90   </li>
  91
  92   <li>If you intend to use Clang's C++ support, you may need to tell it how
  93       to find your C++ standard library headers. In general, Clang will detect
  94       the best version of libstdc++ headers available and use them - it will
  95       look both for system installations of libstdc++ as well as installations
  96       adjacent to Clang itself. If your configuration fits neither of these
  97       scenarios, you can use the <tt>--with-gcc-toolchain</tt> configure option
  98       to tell Clang where the gcc containing the desired libstdc++ is installed.
  99   </li>
 100   <li>Try it out (assuming you add llvm/Debug+Asserts/bin to your path):
 101   <ul>
 102     <li><tt>clang --help</tt></li>
 103     <li><tt>clang file.c -fsyntax-only</tt> (check for correctness)</li>
 104     <li><tt>clang file.c -S -emit-llvm -o -</tt> (print out unoptimized llvm code)</li>
 105     <li><tt>clang file.c -S -emit-llvm -o - -O3</tt></li>
 106     <li><tt>clang file.c -S -O3 -o -</tt> (output native machine code)</li>
 107   </ul>
 108   </li>
 109 </ol>
 110
 111 <p>Note that the C front-end uses LLVM, but does not depend on llvm-gcc. If you
 112 encounter problems with building Clang, make sure you have the latest SVN
 113 version of LLVM. LLVM contains support libraries for Clang that will be updated
 114 as well as development on Clang progresses.</p>
 115
 116 <h3>Simultaneously Building Clang and LLVM:</h3>
 117
 118 <p>Once you have checked out Clang into the llvm source tree it will build along
 119 with the rest of <tt>llvm</tt>. To build all of LLVM and Clang together all at
 120 once simply run <tt>make</tt> from the root LLVM directory.</p>
 121
 122 <p><em>Note:</em> Observe that Clang is technically part of a separate
 123 Subversion repository. As mentioned above, the latest Clang sources are tied to
 124 the latest sources in the LLVM tree. You can update your toplevel LLVM project
 125 and all (possibly unrelated) projects inside it with <tt><b>make
 126 update</b></tt>. This will run <tt>svn update</tt> on all subdirectories related
 127 to subversion. </p>
 128
 129 <h3 id="buildWindows">Using Visual Studio</h3>
 130
 131 <p>The following details setting up for and building Clang on Windows using
 132 Visual Studio:</p>
 133
 134 <ol>
 135   <li>Get the required tools:
 136   <ul>
 137     <li><b>Subversion</b>.  Source code control program.  Get it from:
 138         <a href="http://subversion.tigris.org/getting.html">
 139         http://subversion.tigris.org/getting.html</a></li>
 140     <li><b>CMake</b>.  This is used for generating Visual Studio solution and
 141         project files.  Get it from:
 142         <a href="http://www.cmake.org/cmake/resources/software.html">
 143         http://www.cmake.org/cmake/resources/software.html</a></li>
 144     <li><b>Visual Studio 2012 or later</b></li>
 145     <li><b>Python</b>.  This is needed only if you will be running the tests
 146         (which is essential, if you will be developing for clang).
 147         Get it from:
 148         <a href="http://www.python.org/download/">
 149         http://www.python.org/download/</a></li>
 150     <li><b>GnuWin32 tools</b>
 151         These are also necessary for running the tests.
 152         (Note that the grep from MSYS or Cygwin doesn't work with the tests
 153         because of embedded double-quotes in the search strings.  The GNU
 154         grep does work in this case.)
 155         Get them from <a href="http://getgnuwin32.sourceforge.net/">
 156         http://getgnuwin32.sourceforge.net/</a>.</li>
 157   </ul>
 158   </li>
 159
 160   <li>Checkout LLVM:
 161   <ul>
 162     <li><tt>svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm</tt></li>
 163   </ul>
 164   </li>
 165   <li>Checkout Clang:
 166   <ul>
 167      <li><tt>cd llvm\tools</tt>
 168      <li><tt>svn co http://llvm.org/svn/llvm-project/cfe/trunk clang</tt></li>
 169   </ul>
 170   </li>
 171   <li>Run CMake to generate the Visual Studio solution and project files:
 172   <ul>
 173     <li><tt>cd ..\..</tt>  (back to where you started)</li>
 174     <li><tt>mkdir build</tt> (for building without polluting the source dir)</li>
 175     <li><tt>cd build</tt></li>
 176     <li>If you are using Visual Studio 2012:  <tt>cmake -G "Visual Studio 11" ..\llvm</tt></li>
 177     <li>See the <a href="http://www.llvm.org/docs/CMake.html">LLVM CMake guide</a> for
 178         more information on other configuration options for CMake.</li>
 179     <li>The above, if successful, will have created an LLVM.sln file in the
 180        <tt>build</tt> directory.
 181   </ul>
 182   </li>
 183   <li>Build Clang:
 184   <ul>
 185     <li>Open LLVM.sln in Visual Studio.</li>
 186     <li>Build the "clang" project for just the compiler driver and front end, or
 187       the "ALL_BUILD" project to build everything, including tools.</li>
 188   </ul>
 189   </li>
 190   <li>Try it out (assuming you added llvm/debug/bin to your path).  (See the
 191     running examples from above.)</li>
 192   <li>See <a href="hacking.html#testingWindows">
 193      Hacking on clang - Testing using Visual Studio on Windows</a> for information
 194      on running regression tests on Windows.</li>
 195 </ol>
 196
 197 <p>Note that once you have checked out both llvm and clang, to synchronize
 198 to the latest code base, use the <tt>svn update</tt> command in both the
 199 llvm and llvm\tools\clang directories, as they are separate repositories.</p>
 200
 201 <h2 id="driver">Clang Compiler Driver (Drop-in Substitute for GCC)</h2>
 202
 203 <p>The <tt>clang</tt> tool is the compiler driver and front-end, which is
 204 designed to be a drop-in replacement for the <tt>gcc</tt> command.  Here are
 205 some examples of how to use the high-level driver:
 206 </p>
 207
 208 <pre class="code">
 209 $ <b>cat t.c</b>
 210 #include &lt;stdio.h&gt;
 211 int main(int argc, char **argv) { printf("hello world\n"); }
 212 $ <b>clang t.c</b>
 213 $ <b>./a.out</b>
 214 hello world
 215 </pre>
 216
 217 <p>The 'clang' driver is designed to work as closely to GCC as possible to
 218   maximize portability.  The only major difference between the two is that
 219   Clang defaults to gnu99 mode while GCC defaults to gnu89 mode.  If you see
 220   weird link-time errors relating to inline functions, try passing -std=gnu89
 221   to clang.</p>
 222
 223 <h2>Examples of using Clang</h2>
 224
 225 <!-- Thanks to
 226  http://shiflett.org/blog/2006/oct/formatting-and-highlighting-php-code-listings
 227 Site suggested using pre in CSS, but doesn't work in IE, so went for the <pre>
 228 tag. -->
 229
 230 <pre class="code">
 231 $ <b>cat ~/t.c</b>
 232 typedef float V __attribute__((vector_size(16)));
 233 V foo(V a, V b) { return a+b*a; }
 234 </pre>
 235
 236
 237 <h3>Preprocessing:</h3>
 238
 239 <pre class="code">
 240 $ <b>clang ~/t.c -E</b>
 241 # 1 "/Users/sabre/t.c" 1
 242
 243 typedef float V __attribute__((vector_size(16)));
 244
 245 V foo(V a, V b) { return a+b*a; }
 246 </pre>
 247
 248
 249 <h3>Type checking:</h3>
 250
 251 <pre class="code">
 252 $ <b>clang -fsyntax-only ~/t.c</b>
 253 </pre>
 254
 255
 256 <h3>GCC options:</h3>
 257
 258 <pre class="code">
 259 $ <b>clang -fsyntax-only ~/t.c -pedantic</b>
 260 /Users/sabre/t.c:2:17: <span style="color:magenta">warning:</span> extension used
 261 <span style="color:darkgreen">typedef float V __attribute__((vector_size(16)));</span>
 262 <span style="color:blue">                ^</span>
 263 1 diagnostic generated.
 264 </pre>
 265
 266
 267 <h3>Pretty printing from the AST:</h3>
 268
 269 <p>Note, the <tt>-cc1</tt> argument indicates the compiler front-end, and
 270 not the driver, should be run. The compiler front-end has several additional
 271 Clang specific features which are not exposed through the GCC compatible driver
 272 interface.</p>
 273
 274 <pre class="code">
 275 $ <b>clang -cc1 ~/t.c -ast-print</b>
 276 typedef float V __attribute__(( vector_size(16) ));
 277 V foo(V a, V b) {
 278    return a + b * a;
 279 }
 280 </pre>
 281
 282
 283 <h3>Code generation with LLVM:</h3>
 284
 285 <pre class="code">
 286 $ <b>clang ~/t.c -S -emit-llvm -o -</b>
 287 define &lt;4 x float&gt; @foo(&lt;4 x float&gt; %a, &lt;4 x float&gt; %b) {
 288 entry:
 289          %mul = mul &lt;4 x float&gt; %b, %a
 290          %add = add &lt;4 x float&gt; %mul, %a
 291          ret &lt;4 x float&gt; %add
 292 }
 293 $ <b>clang -fomit-frame-pointer -O3 -S -o - t.c</b> <i># On x86_64</i>
 294 ...
 295 _foo:
 296 Leh_func_begin1:
 297         mulps   %xmm0, %xmm1
 298         addps   %xmm1, %xmm0
 299         ret
 300 Leh_func_end1:
 301 </pre>
 302
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