229 lines
7.2 KiB
HTML
229 lines
7.2 KiB
HTML
<!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>Building clang while building llvm:</h3>
|
|
<p>Since you've checked out clang into the llvm source tree you can
|
|
build them all at once with a simple Makefile change. This moves
|
|
Step 1 above to Step 4.</p>
|
|
<ul>
|
|
<li><tt>cd llvm/tools</tt></li>
|
|
<li>then edit <tt>Makefile</tt> to have a clang target in <tt>PARALLEL_DIRS</tt>
|
|
just like <tt>llvm-config</tt></li>
|
|
<li>then just build llvm normally as above and clang will build at
|
|
the same time</li>
|
|
</ul>
|
|
|
|
<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>
|
|
|
|
<h3>GCC "Emulation" Driver</h3>
|
|
|
|
While the <tt>clang</tt> executable is a compiler driver 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>. There is interest in developing such
|
|
a driver for clang, but in the interim the clang source tree includes a Python
|
|
script <tt>ccc</tt> in the <tt>utils</tt> subdirectory that provides some of
|
|
this functionality (the script is intended to be used where GCC's <tt>cc</tt>
|
|
could be used). It is currently a work in progress, and eventually will likely
|
|
be replaced by a more complete driver.
|
|
|
|
<p>Example use:</p>
|
|
|
|
<pre class="code">
|
|
$ <b>ccc t.c</b>
|
|
clang -emit-llvm-bc -o t.o -U__GNUC__ t.c
|
|
llvm-ld -native -o a.out t.o
|
|
$ <b>ls</b>
|
|
a.out a.out.bc t.c t.o
|
|
</pre>
|
|
|
|
|
|
|
|
|
|
</div>
|
|
</body>
|
|
</html>
|