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+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
+ "http://www.w3.org/TR/html4/strict.dtd">
+<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 <em>still very early work</em> and is under heavy development. In particular,
+there is no real C++ support yet (this is obviously a big project), and C/ObjC
+support is still missing some features. Some of the more notable missing pieces
+of C support are:</p>
+
+<ol>
+ <li>The semantic analyzer does not produce all of the warnings and errors it
+ should.</li>
+ <li>The LLVM code generator is still missing important features. clang is not
+ ready to be used as a general purpose C code generator yet, but if you
+ hit problems and report them to cfe-dev, we'll fix them :).</li>
+ <li>We don't consider the API to be stable yet, and reserve the right to
+ change fundamental things.</li>
+</ol>
+
+<p>Our plan is to continue chipping away at these issues until C works really
+well, but we'd love help from other interested contributors. We expect C to be
+in good shape by mid to late 2008.</p>
+
+<h3><a name="build">Building clang / working with the code</a></h3>
+
+<p>If you would like to check out and build the project, the current scheme
+is:</p>
+
+<ol>
+ <li><a href="http://www.llvm.org/docs/GettingStarted.html#checkout">Checkout
+ and build LLVM</a> from SVN head:</li>
+
+ <ul>
+ <li><tt>svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm</tt></li>
+ <li><tt>cd llvm</tt></li>
+ <li><tt>./configure; make</tt></li>
+ </ul>
+ <li>Checkout clang:</li>
+ <ul>
+ <li>From within the <tt>llvm</tt> directory (where you
+ built llvm):</li>
+ <li><tt>cd llvm/tools</tt>
+ <li><tt>svn co http://llvm.org/svn/llvm-project/cfe/trunk clang</tt></li>
+
+ </ul>
+ <li>Non-mac users: Paths to system header files are currently hard coded
+ into clang; as a result, if clang can't find your system headers,
+ please follow these instructions:</li>
+
+ <ul>
+ <li>'<tt>touch empty.c; gcc -v empty.c -fsyntax-only</tt>' to get the
+ path.</li>
+ <li>Look for the comment "FIXME: temporary hack:
+ hard-coded paths" in <tt>clang/Driver/clang.cpp</tt> and
+ change the lines below to include that path.</li>
+ </ul>
+
+ <li>Build clang:</li>
+ <ul>
+ <li><tt>cd clang</tt> (assuming that you are in <tt>llvm/tools</tt>)</li>
+ <li><tt>make</tt> (this will give you a debug build)</li>
+ </ul>
+
+ <li>Try it out (assuming you add llvm/Debug/bin to your path):</li>
+ <ul>
+ <li><tt>clang --help</tt></li>
+ <li><tt>clang file.c -fsyntax-only</tt> (check for correctness)</li>
+ <li><tt>clang file.c -ast-dump</tt> (internal debug dump of ast)</li>
+ <li><tt>clang 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 file.c -emit-llvm</tt> (print out unoptimized llvm code)</li>
+ <li><tt>clang file.c -emit-llvm | llvm-as | opt -std-compile-opts |
+ llvm-dis</tt> (print out optimized llvm code)</li>
+ <li><tt>clang file.c -emit-llvm | llvm-as | opt -std-compile-opts | llc
+ > file.s</tt> (output native machine code)</li>
+ </ul>
+</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>Examples of using clang</h3>
+
+<p>The clang driver takes a lot of GCC compatible options, which you can see
+with 'clang --help'. Here are a few examples:</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>
+
+
+<h4>Preprocessing:</h4>
+
+<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>
+
+
+<h4>Type checking:</h4>
+
+<pre class="code">
+$ <b>clang -fsyntax-only ~/t.c</b>
+</pre>
+
+
+<h4>GCC options:</h4>
+
+<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>
+
+
+<h4>Pretty printing from the AST:</h4>
+
+<pre class="code">
+$ <b>clang ~/t.c -ast-print</b>
+typedef float V __attribute__(( vector_size(16) ));
+V foo(V a, V b) {
+ return a + b * a;
+}
+</pre>
+
+
+<h4>Code generation with LLVM:</h4>
+
+<pre class="code">
+$ <b>clang ~/t.c -emit-llvm | 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 ~/t.c -emit-llvm | llvm-as | opt -std-compile-opts | llc -march=ppc32 -mcpu=g5</b>
+..
+_foo:
+ vmaddfp v2, v3, v2, v2
+ blr
+$ <b>clang ~/t.c -emit-llvm | llvm-as | opt -std-compile-opts | llc -march=x86 -mcpu=yonah</b>
+..
+_foo:
+ mulps %xmm0, %xmm1
+ addps %xmm0, %xmm1
+ movaps %xmm1, %xmm0
+ ret
+</pre>
+
+</div>
+</body>
+</html>