www/get_started.html - clang - Git at Google

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 <div id="content">

 <h1>Getting Started: Building and Running Clang</h1>

 <p>This page gives you the shortest path to checking out Clang and demos a few
 options.  This should get you up and running with the minimum of muss and fuss.
 If you like what you see, please consider <a href="get_involved.html">getting
 involved</a> with the Clang community.</p>

 <h2>A Word of Warning</h2>

 <p>While this work aims to provide a fully functional C/C++/ObjC front-end, it
 is still relatively new and under heavy development. Currently we believe clang
 to be very usable as a C and Objective-C compiler, however there is no real C++
 support yet (this is obviously a big project). Additionally, for C and
 Objective-C:</p>

 <ol>
   <li>The semantic analyzer does not produce all of the warnings it should.</li>
   <li>We don't consider the API to be stable yet, and reserve the right to
       change fundamental things.</li>
   <li>Only the X86-32 and X86-64 targets have been well tested.</li>
 </ol>

 <p>If you run into problems, please file
 bugs in <a href="http://llvm.org/bugs/">LLVM Bugzilla</a> or bring up the issue
 on the
 <a href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev">Clang development
 mailing list</a>.</p>

 <h2 id="build">Building Clang and Working with the Code</h2>

 <h3 id="buildNix">On Unix-like Systems</h3>

 <p>If you would like to check out and build Clang, the current procedure is as
 follows:</p>

 <ol>
   <li>Get the required tools.
   <ul>
     <li>See
       <a href="http://llvm.org/docs/GettingStarted.html#requirements">
       Getting Started with the LLVM System - Requirements</a>.</li>
     <li>Note also that Python is needed for running the test suite.
       Get it at: <a href="http://www.python.org/download">
       http://www.python.org/download</a></li>
   </ul>

   <li>Checkout LLVM:</li>
   <ul>
     <li>Change directory to where you want the llvm directory placed.</li>
     <li><tt>svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm</tt></li>
   </ul>
   <li>Checkout Clang:</li>
   <ul>
     <li><tt>cd llvm/tools</tt>
     <li><tt>svn co http://llvm.org/svn/llvm-project/cfe/trunk clang</tt></li>
   </ul>
   <li>Build LLVM and Clang:</li>
   <ul>
     <li><tt>cd ..</tt>  (back to llvm)</li>
     <li><tt>./configure</tt></li>
     <li><tt>make</tt></li>
     <li>This builds both LLVM and Clang for debug mode.</li>
     <li>Note: For subsequent Clang development, you can just do make at the
     clang directory level.</li>
   </ul>
   <li>If you intend to work on Clang C++ support, you may need to tell it how
       to find your C++ standard library headers.  If Clang cannot find your
       system libstdc++ headers, please follow these instructions:</li>
   <ul>
     <li>'<tt>touch empty.cpp; gcc -v empty.cpp -fsyntax-only</tt>' to get the
     path.</li>
     <li>Look for the comment "FIXME: temporary hack:
     hard-coded paths" in <tt>clang/lib/Frontend/InitHeaderSearch.cpp</tt> and
     change the lines below to include that path.</li>
   </ul>
   <li>Try it out (assuming you add llvm/Debug/bin to your path):</li>
   <ul>
     <li><tt>clang-cc --help</tt></li>
     <li><tt>clang-cc file.c -fsyntax-only</tt> (check for correctness)</li>
     <li><tt>clang-cc file.c -ast-dump</tt> (internal debug dump of ast)</li>
     <li><tt>clang-cc file.c -ast-view</tt> (<a
     href="http://llvm.org/docs/ProgrammersManual.html#ViewGraph">set up graphviz
      and rebuild llvm first</a>)</li>
     <li><tt>clang-cc file.c -emit-llvm</tt> (print out unoptimized llvm code)</li>
     <li><tt>clang-cc file.c -emit-llvm -o - | llvm-as | opt -std-compile-opts |
          llvm-dis</tt> (print out optimized llvm code)</li>
     <li><tt>clang-cc file.c -emit-llvm -o - | llvm-as | opt -std-compile-opts | llc
          &gt; file.s</tt> (output native machine code)</li>
   </ul>
   <p><em>Note</em>: Here <tt>clang-cc</tt> is the "low-level" frontend
   executable that is similar in purpose to <tt>cc1</tt>. Clang also has a <a
   href="#driver">high-level compiler driver</a> that acts as a drop-in
   replacement for <tt>gcc</tt>.
 </ol>

 <p>Note that the C front-end uses LLVM, but does not depend on llvm-gcc. If you
 encounter problems with building Clang, make sure you have the latest SVN
 version of LLVM. LLVM contains support libraries for Clang that will be updated
 as well as development on Clang progresses.</p>

 <h3>Simultaneously Building Clang and LLVM:</h3>

 <p>Once you have checked out Clang into the llvm source tree it will build along
 with the rest of <tt>llvm</tt>. To build all of LLVM and Clang together all at
 once simply run <tt>make</tt> from the root LLVM directory.</p>

 <p><em>Note:</em> Observe that Clang is technically part of a separate
 Subversion repository. As mentioned above, the latest Clang sources are tied to
 the latest sources in the LLVM tree. You can update your toplevel LLVM project
 and all (possibly unrelated) projects inside it with <tt><b>make
 update</b></tt>. This will run <tt>svn update</tt> on all subdirectories related
 to subversion. </p>

 <h3 id="buildWindows">Using Visual Studio</h3>

 <p>The following details setting up for and building Clang on Windows using
 Visual Studio:</p>

 <ol>
   <li>Get the required tools:</li>
   <ul>
     <li><b>Subversion</b>.  Source code control program.  Get it from:
         <a href="http://subversion.tigris.org/getting.html">
         http://subversion.tigris.org/getting.html</a></li>
     <li><b>cmake</b>.  This is used for generating Visual Studio solution and
         project files.  Get it from:
         <a href="http://www.cmake.org/cmake/resources/software.html">
         http://www.cmake.org/cmake/resources/software.html</a></li>
     <li><b>Visual Studio 2005</b>
         (VS 2008 may work also - cmake outputs VS2005 project files)</li>
     <li><b>Python</b>.  This is needed only if you will be running the tests
         (which is essential, if you will be developing for clang).
         Get it from:
         <a href="http://www.python.org/download">
         http://www.python.org/download</a></li>
     <li><b>GnuWin32 tools</b>
         These are also necessary for running the tests.
         (Note that the grep from MSYS or Cygwin doesn't work with the tests
         because of embedded double-quotes in the search strings.  The GNU
         grep does work in this case.)
         Get them from <a href="http://getgnuwin32.sourceforge.net">
         http://getgnuwin32.sourceforge.net</a>.</li>
   </ul>

   <li>Checkout LLVM:</li>
   <ul>
     <li><tt>svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm</tt></li>
   </ul>
   <li>Checkout Clang:</li>
   <ul>
      <li><tt>cd llvm\tools</tt>
      <li><tt>svn co http://llvm.org/svn/llvm-project/cfe/trunk clang</tt></li>
   </ul>
   <li>Run cmake to generate the Visual Studio solution and project files:</li>
   <ul>
     <li><tt>cd ..</tt>  (Change directory back to the llvm top.)</li>
     <li><tt>cmake .</tt></li>
     <li>The above, if successful, will have created an LLVM.sln file in the
        llvm directory.
   </ul>
   <li>Build Clang:</li>
   <ul>
     <li>Open LLVM.sln in Visual Studio.</li>
     <li>Build the "clang-cc" project for just the compiler front end.
        Alternatively, build the "clang" project for the compiler driver
        (note that the driver is currently broken on Windows),
        or the "ALL_BUILD" project to build everything, including tools.</li>
   </ul>
   <li>Try it out (assuming you added llvm/debug/bin to your path).  (See the
     running examples from above.)</li>
   <li>See <a href="hacking.html#testingWindows">
      Hacking on clang - Testing using Visual Studio on Windows</a> for information
      on running regression tests on Windows.</li>
 </ol>

 <p>Note that once you have checked out both llvm and clang, to synchronize
 to the latest code base, use the <tt>svn update</tt> command in both the
 llvm and llvm\tools\clang directories, as they are separate repositories.</p>

 <a name="driver"><h2>High-Level Compiler Driver (Drop-in Substitute for GCC)</h2></a>

 <p>While the <tt>clang-cc</tt> executable is a low-level frontend executable
 that can perform code generation, program analysis, and other actions, it is not
 designed to be a drop-in replacement for GCC's <tt>cc</tt>. For this purpose,
 use the high-level driver, aptly named <tt>clang</tt>.  Here are some
 examples of how to use the high-level driver:
 </p>

 <pre class="code">
 $ <b>cat t.c</b>
 #include &lt;stdio.h&gt;
 int main(int argc, char **argv) { printf("hello world\n"); }
 $ <b>clang t.c</b>
 $ <b>./a.out</b>
 hello world
 </pre>

 <h2>Examples of using Clang</h2>

 <p>The high-level driver <tt>clang</tt> is designed to understand most of GCC's
 options, and the lower-level <tt>clang-cc</tt> executable also directly takes
 many of GCC's options. You can see which options <tt>clang-cc</tt> accepts with
 '<tt>clang-cc --help</tt>'. Here are a few examples of using <tt>clang</tt> and
 <tt>clang-cc</tt>:</p>

 <!-- Thanks to
  http://shiflett.org/blog/2006/oct/formatting-and-highlighting-php-code-listings
 Site suggested using pre in CSS, but doesn't work in IE, so went for the <pre>
 tag. -->

 <pre class="code">
 $ <b>cat ~/t.c</b>
 typedef float V __attribute__((vector_size(16)));
 V foo(V a, V b) { return a+b*a; }
 </pre>


 <h3>Preprocessing:</h3>

 <pre class="code">
 $ <b>clang ~/t.c -E</b>
 # 1 "/Users/sabre/t.c" 1

 typedef float V __attribute__((vector_size(16)));

 V foo(V a, V b) { return a+b*a; }
 </pre>


 <h3>Type checking:</h3>

 <pre class="code">
 $ <b>clang -fsyntax-only ~/t.c</b>
 </pre>


 <h3>GCC options:</h3>

 <pre class="code">
 $ <b>clang -fsyntax-only ~/t.c -pedantic</b>
 /Users/sabre/t.c:2:17: warning: extension used
 typedef float V __attribute__((vector_size(16)));
                 ^
 1 diagnostic generated.
 </pre>


 <h3>Pretty printing from the AST:</h3>

 <pre class="code">
 $ <b>clang-cc ~/t.c -ast-print</b>
 typedef float V __attribute__(( vector_size(16) ));
 V foo(V a, V b) {
    return a + b * a;
 }
 </pre>


 <h3>Code generation with LLVM:</h3>

 <pre class="code">
 $ <b>clang-cc ~/t.c -emit-llvm -o - | llvm-as | opt -std-compile-opts | llvm-dis</b>
 define &lt;4 x float&gt; @foo(&lt;4 x float&gt; %a, &lt;4 x float&gt; %b) {
 entry:
          %mul = mul &lt;4 x float&gt; %b, %a
          %add = add &lt;4 x float&gt; %mul, %a
          ret &lt;4 x float&gt; %add
 }
 $ <b>clang-cc ~/t.c -emit-llvm -o - | llvm-as | opt -std-compile-opts | llc -march=ppc32 -mcpu=g5</b>
 ..
 _foo:
          vmaddfp v2, v3, v2, v2
          blr
 $ <b>clang-cc ~/t.c -emit-llvm -o - | llvm-as | opt -std-compile-opts | llc -march=x86 -mcpu=yonah</b>
 ..
 _foo:
          mulps %xmm0, %xmm1
          addps %xmm0, %xmm1
          movaps %xmm1, %xmm0
          ret
 </pre>

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	<html>
	<head>
	<META http-equiv="Content-Type" content="text/html; charset=ISO-8859-1" />
	<title>Clang - Getting Started</title>
	<link type="text/css" rel="stylesheet" href="menu.css" />
	<link type="text/css" rel="stylesheet" href="content.css" />
	</head>
	<body>

	<!--#include virtual="menu.html.incl"-->

	<div id="content">

	<h1>Getting Started: Building and Running Clang</h1>

	<p>This page gives you the shortest path to checking out Clang and demos a few
	options. This should get you up and running with the minimum of muss and fuss.
	If you like what you see, please consider <a href="get_involved.html">getting
	involved</a> with the Clang community.</p>

	<h2>A Word of Warning</h2>

	<p>While this work aims to provide a fully functional C/C++/ObjC front-end, it
	is still relatively new and under heavy development. Currently we believe clang
	to be very usable as a C and Objective-C compiler, however there is no real C++
	support yet (this is obviously a big project). Additionally, for C and
	Objective-C:</p>

	<ol>
	<li>The semantic analyzer does not produce all of the warnings it should.</li>
	<li>We don't consider the API to be stable yet, and reserve the right to
	change fundamental things.</li>
	<li>Only the X86-32 and X86-64 targets have been well tested.</li>
	</ol>

	<p>If you run into problems, please file
	bugs in <a href="http://llvm.org/bugs/">LLVM Bugzilla</a> or bring up the issue
	on the
	<a href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev">Clang development
	mailing list</a>.</p>

	<h2 id="build">Building Clang and Working with the Code</h2>

	<h3 id="buildNix">On Unix-like Systems</h3>

	<p>If you would like to check out and build Clang, the current procedure is as
	follows:</p>

	<ol>
	<li>Get the required tools.
	<ul>
	<li>See
	<a href="http://llvm.org/docs/GettingStarted.html#requirements">
	Getting Started with the LLVM System - Requirements</a>.</li>
	<li>Note also that Python is needed for running the test suite.
	Get it at: <a href="http://www.python.org/download">
	http://www.python.org/download</a></li>
	</ul>

	<li>Checkout LLVM:</li>
	<ul>
	<li>Change directory to where you want the llvm directory placed.</li>
	<li><tt>svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm</tt></li>
	</ul>
	<li>Checkout Clang:</li>
	<ul>
	<li><tt>cd llvm/tools</tt>
	<li><tt>svn co http://llvm.org/svn/llvm-project/cfe/trunk clang</tt></li>
	</ul>
	<li>Build LLVM and Clang:</li>
	<ul>
	<li><tt>cd ..</tt> (back to llvm)</li>
	<li><tt>./configure</tt></li>
	<li><tt>make</tt></li>
	<li>This builds both LLVM and Clang for debug mode.</li>
	<li>Note: For subsequent Clang development, you can just do make at the
	clang directory level.</li>
	</ul>
	<li>If you intend to work on Clang C++ support, you may need to tell it how
	to find your C++ standard library headers. If Clang cannot find your
	system libstdc++ headers, please follow these instructions:</li>
	<ul>
	<li>'<tt>touch empty.cpp; gcc -v empty.cpp -fsyntax-only</tt>' to get the
	path.</li>
	<li>Look for the comment "FIXME: temporary hack:
	hard-coded paths" in <tt>clang/lib/Frontend/InitHeaderSearch.cpp</tt> and
	change the lines below to include that path.</li>
	</ul>
	<li>Try it out (assuming you add llvm/Debug/bin to your path):</li>
	<ul>
	<li><tt>clang-cc --help</tt></li>
	<li><tt>clang-cc file.c -fsyntax-only</tt> (check for correctness)</li>
	<li><tt>clang-cc file.c -ast-dump</tt> (internal debug dump of ast)</li>
	<li><tt>clang-cc file.c -ast-view</tt> (<a
	href="http://llvm.org/docs/ProgrammersManual.html#ViewGraph">set up graphviz
	and rebuild llvm first</a>)</li>
	<li><tt>clang-cc file.c -emit-llvm</tt> (print out unoptimized llvm code)</li>
	<li><tt>clang-cc file.c -emit-llvm -o - \| llvm-as \| opt -std-compile-opts \|
	llvm-dis</tt> (print out optimized llvm code)</li>
	<li><tt>clang-cc file.c -emit-llvm -o - \| llvm-as \| opt -std-compile-opts \| llc
	> file.s</tt> (output native machine code)</li>
	</ul>
	<p><em>Note</em>: Here <tt>clang-cc</tt> is the "low-level" frontend
	executable that is similar in purpose to <tt>cc1</tt>. Clang also has a <a
	href="#driver">high-level compiler driver</a> that acts as a drop-in
	replacement for <tt>gcc</tt>.
	</ol>

	<p>Note that the C front-end uses LLVM, but does not depend on llvm-gcc. If you
	encounter problems with building Clang, make sure you have the latest SVN
	version of LLVM. LLVM contains support libraries for Clang that will be updated
	as well as development on Clang progresses.</p>

	<h3>Simultaneously Building Clang and LLVM:</h3>

	<p>Once you have checked out Clang into the llvm source tree it will build along
	with the rest of <tt>llvm</tt>. To build all of LLVM and Clang together all at
	once simply run <tt>make</tt> from the root LLVM directory.</p>

	<p><em>Note:</em> Observe that Clang is technically part of a separate
	Subversion repository. As mentioned above, the latest Clang sources are tied to
	the latest sources in the LLVM tree. You can update your toplevel LLVM project
	and all (possibly unrelated) projects inside it with <tt><b>make
	update</b></tt>. This will run <tt>svn update</tt> on all subdirectories related
	to subversion. </p>

	<h3 id="buildWindows">Using Visual Studio</h3>

	<p>The following details setting up for and building Clang on Windows using
	Visual Studio:</p>

	<ol>
	<li>Get the required tools:</li>
	<ul>
	<li><b>Subversion</b>. Source code control program. Get it from:
	<a href="http://subversion.tigris.org/getting.html">
	http://subversion.tigris.org/getting.html</a></li>
	<li><b>cmake</b>. This is used for generating Visual Studio solution and
	project files. Get it from:
	<a href="http://www.cmake.org/cmake/resources/software.html">
	http://www.cmake.org/cmake/resources/software.html</a></li>
	<li><b>Visual Studio 2005</b>
	(VS 2008 may work also - cmake outputs VS2005 project files)</li>
	<li><b>Python</b>. This is needed only if you will be running the tests
	(which is essential, if you will be developing for clang).
	Get it from:
	<a href="http://www.python.org/download">
	http://www.python.org/download</a></li>
	<li><b>GnuWin32 tools</b>
	These are also necessary for running the tests.
	(Note that the grep from MSYS or Cygwin doesn't work with the tests
	because of embedded double-quotes in the search strings. The GNU
	grep does work in this case.)
	Get them from <a href="http://getgnuwin32.sourceforge.net">
	http://getgnuwin32.sourceforge.net</a>.</li>
	</ul>

	<li>Checkout LLVM:</li>
	<ul>
	<li><tt>svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm</tt></li>
	</ul>
	<li>Checkout Clang:</li>
	<ul>
	<li><tt>cd llvm\tools</tt>
	<li><tt>svn co http://llvm.org/svn/llvm-project/cfe/trunk clang</tt></li>
	</ul>
	<li>Run cmake to generate the Visual Studio solution and project files:</li>
	<ul>
	<li><tt>cd ..</tt> (Change directory back to the llvm top.)</li>
	<li><tt>cmake .</tt></li>
	<li>The above, if successful, will have created an LLVM.sln file in the
	llvm directory.
	</ul>
	<li>Build Clang:</li>
	<ul>
	<li>Open LLVM.sln in Visual Studio.</li>
	<li>Build the "clang-cc" project for just the compiler front end.
	Alternatively, build the "clang" project for the compiler driver
	(note that the driver is currently broken on Windows),
	or the "ALL_BUILD" project to build everything, including tools.</li>
	</ul>
	<li>Try it out (assuming you added llvm/debug/bin to your path). (See the
	running examples from above.)</li>
	<li>See <a href="hacking.html#testingWindows">
	Hacking on clang - Testing using Visual Studio on Windows</a> for information
	on running regression tests on Windows.</li>
	</ol>

	<p>Note that once you have checked out both llvm and clang, to synchronize
	to the latest code base, use the <tt>svn update</tt> command in both the
	llvm and llvm\tools\clang directories, as they are separate repositories.</p>

	<a name="driver"><h2>High-Level Compiler Driver (Drop-in Substitute for GCC)</h2></a>

	<p>While the <tt>clang-cc</tt> executable is a low-level frontend executable
	that can perform code generation, program analysis, and other actions, it is not
	designed to be a drop-in replacement for GCC's <tt>cc</tt>. For this purpose,
	use the high-level driver, aptly named <tt>clang</tt>. Here are some
	examples of how to use the high-level driver:
	</p>

	<pre class="code">
	$ <b>cat t.c</b>
	#include <stdio.h>
	int main(int argc, char **argv) { printf("hello world\n"); }
	$ <b>clang t.c</b>
	$ <b>./a.out</b>
	hello world
	</pre>

	<h2>Examples of using Clang</h2>

	<p>The high-level driver <tt>clang</tt> is designed to understand most of GCC's
	options, and the lower-level <tt>clang-cc</tt> executable also directly takes
	many of GCC's options. You can see which options <tt>clang-cc</tt> accepts with
	'<tt>clang-cc --help</tt>'. Here are a few examples of using <tt>clang</tt> and
	<tt>clang-cc</tt>:</p>

	<!-- Thanks to
	http://shiflett.org/blog/2006/oct/formatting-and-highlighting-php-code-listings
	Site suggested using pre in CSS, but doesn't work in IE, so went for the <pre>
	tag. -->

	<pre class="code">
	$ <b>cat ~/t.c</b>
	typedef float V __attribute__((vector_size(16)));
	V foo(V a, V b) { return a+b*a; }
	</pre>


	<h3>Preprocessing:</h3>

	<pre class="code">
	$ <b>clang ~/t.c -E</b>
	# 1 "/Users/sabre/t.c" 1

	typedef float V __attribute__((vector_size(16)));

	V foo(V a, V b) { return a+b*a; }
	</pre>


	<h3>Type checking:</h3>

	<pre class="code">
	$ <b>clang -fsyntax-only ~/t.c</b>
	</pre>


	<h3>GCC options:</h3>

	<pre class="code">
	$ <b>clang -fsyntax-only ~/t.c -pedantic</b>
	/Users/sabre/t.c:2:17: warning: extension used
	typedef float V __attribute__((vector_size(16)));
	^
	1 diagnostic generated.
	</pre>


	<h3>Pretty printing from the AST:</h3>

	<pre class="code">
	$ <b>clang-cc ~/t.c -ast-print</b>
	typedef float V __attribute__(( vector_size(16) ));
	V foo(V a, V b) {
	return a + b * a;
	}
	</pre>


	<h3>Code generation with LLVM:</h3>

	<pre class="code">
	$ <b>clang-cc ~/t.c -emit-llvm -o - \| llvm-as \| opt -std-compile-opts \| llvm-dis</b>
	define <4 x float> @foo(<4 x float> %a, <4 x float> %b) {
	entry:
	%mul = mul <4 x float> %b, %a
	%add = add <4 x float> %mul, %a
	ret <4 x float> %add
	}
	$ <b>clang-cc ~/t.c -emit-llvm -o - \| llvm-as \| opt -std-compile-opts \| llc -march=ppc32 -mcpu=g5</b>
	..
	_foo:
	vmaddfp v2, v3, v2, v2
	blr
	$ <b>clang-cc ~/t.c -emit-llvm -o - \| llvm-as \| opt -std-compile-opts \| llc -march=x86 -mcpu=yonah</b>
	..
	_foo:
	mulps %xmm0, %xmm1
	addps %xmm0, %xmm1
	movaps %xmm1, %xmm0
	ret
	</pre>

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