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 <div class="doc_title">
   Building the LLVM GCC Front-End
 </div>

 <ol>
   <li><a href="#instructions">Building llvm-gcc from Source</a></li>
   <li><a href="#ada">Building the Ada front-end</a></li>
   <li><a href="#fortran">Building the Fortran front-end</a></li>
   <li><a href="#license">License Information</a></li>
 </ol>

 <div class="doc_author">
   <p>Written by the LLVM Team</p>
 </div>

 <!-- *********************************************************************** -->
 <h1><a name="instructions">Building llvm-gcc from Source</a></h1>
 <!-- *********************************************************************** -->

 <div class="doc_text">

 <p>This section describes how to acquire and build llvm-gcc 4.2, which is based
 on the GCC 4.2.1 front-end.  Supported languages are Ada, C, C++, Fortran,
 Objective-C and Objective-C++.  Note that the instructions for building these
 front-ends are completely different (and much easier!) than those for building
 llvm-gcc3 in the past.</p>

 <ol>
   <li><p>Retrieve the appropriate llvm-gcc-4.2-<i>version</i>.source.tar.gz
          archive from the <a href="http://llvm.org/releases/">LLVM web
          site</a>.</p>

       <p>It is also possible to download the sources of the llvm-gcc front end
          from a read-only mirror using subversion.  To check out the 4.2 code
          for first time use:</p>

 <div class="doc_code">
 <pre>
 svn co http://llvm.org/svn/llvm-project/llvm-gcc-4.2/trunk <i>dst-directory</i>
 </pre>
 </div>

       <p>After that, the code can be be updated in the destination directory
          using:</p>

 <div class="doc_code">
 <pre>svn update</pre>
 </div>

       <p>The mirror is brought up to date every evening.</p></li>

   <li>Follow the directions in the top-level <tt>README.LLVM</tt> file for
       up-to-date instructions on how to build llvm-gcc.  See below for building
       with support for Ada or Fortran.
 </ol>

 </div>

 <!-- *********************************************************************** -->
 <h1><a name="ada">Building the Ada front-end</a></h1>
 <!-- *********************************************************************** -->

 <div class="doc_text">
 <p>Building with support for Ada amounts to following the directions in the
 top-level <tt>README.LLVM</tt> file, adding ",ada" to EXTRALANGS, for example:
 <tt>EXTRALANGS=,ada</tt></p>

 <p>There are some complications however:</p>

 <ol>
   <li><p>The only platform for which the Ada front-end is known to build is
       32 bit intel x86 running linux.  It is unlikely to build for other
       systems without some work.</p></li>
   <li><p>The build requires having a compiler that supports Ada, C and C++.
       The Ada front-end is written in Ada so an Ada compiler is needed to
       build it.  Compilers known to work with the
       <a href="http://llvm.org/releases/download.html">LLVM 2.7 release</a>
       are <a href="http://gcc.gnu.org/releases.html">gcc-4.2</a> and the
       2005, 2006 and 2007 versions of the
       <a href="http://libre.adacore.com/">GNAT GPL Edition</a>.
       <b>GNAT GPL 2008, gcc-4.3 and later will not work</b>.
       The LLVM parts of llvm-gcc are written in C++ so a C++ compiler is
       needed to build them.  The rest of gcc is written in C.
       Some linux distributions provide a version of gcc that supports all
       three languages (the Ada part often comes as an add-on package to
       the rest of gcc).  Otherwise it is possible to combine two versions
       of gcc, one that supports Ada and C (such as the
       <a href="http://libre.adacore.com/">2007 GNAT GPL Edition</a>)
       and another which supports C++, see below.</p></li>
   <li><p>Because the Ada front-end is experimental, it is wise to build the
       compiler with checking enabled.  This causes it to run much slower, but
       helps catch mistakes in the compiler (please report any problems using
       <a href="http://llvm.org/bugs">LLVM bugzilla</a>).</p></li>
   <li><p>The Ada front-end <a href="http://llvm.org/PR2007">fails to
       bootstrap</a>, due to lack of LLVM support for
       <tt>setjmp</tt>/<tt>longjmp</tt> style exception handling (used
       internally by the compiler), so you must specify
       <tt>--disable-bootstrap</tt>.</p></li>
 </ol>

 <p>Supposing appropriate compilers are available, llvm-gcc with Ada support can
    be built on an x86-32 linux box using the following recipe:</p>

 <ol>
   <li><p>Download the <a href="http://llvm.org/releases/download.html">LLVM source</a>
       and unpack it:</p>

 <pre class="doc_code">
 wget http://llvm.org/releases/2.7/llvm-2.7.tgz
 tar xzf llvm-2.7.tgz
 mv llvm-2.7 llvm
 </pre>

       <p>or <a href="GettingStarted.html#checkout">check out the
       latest version from subversion</a>:</p>

 <pre class="doc_code">svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm</pre>

       </li>

   <li><p>Download the
       <a href="http://llvm.org/releases/download.html">llvm-gcc-4.2 source</a>
       and unpack it:</p>

 <pre class="doc_code">
 wget http://llvm.org/releases/2.7/llvm-gcc-4.2-2.7.source.tgz
 tar xzf llvm-gcc-4.2-2.7.source.tgz
 mv llvm-gcc-4.2-2.7.source llvm-gcc-4.2
 </pre>

       <p>or <a href="GettingStarted.html#checkout">check out the
       latest version from subversion</a>:</p>

 <pre class="doc_code">
 svn co http://llvm.org/svn/llvm-project/llvm-gcc-4.2/trunk llvm-gcc-4.2
 </pre>
       </li>

   <li><p>Make a build directory <tt>llvm-objects</tt> for llvm and make it the
       current directory:</p>

 <pre class="doc_code">
 mkdir llvm-objects
 cd llvm-objects
 </pre>
       </li>

   <li><p>Configure LLVM (here it is configured to install into <tt>/usr/local</tt>):</p>

 <pre class="doc_code">
 ../llvm/configure --prefix=<b>/usr/local</b> --enable-optimized --enable-assertions
 </pre>

       <p>If you have a multi-compiler setup and the C++ compiler is not the
       default, then you can configure like this:</p>

 <pre class="doc_code">
 CXX=<b>PATH_TO_C++_COMPILER</b> ../llvm/configure --prefix=<b>/usr/local</b> --enable-optimized --enable-assertions
 </pre>

       <p>To compile without checking (not recommended), replace
       <tt>--enable-assertions</tt> with <tt>--disable-assertions</tt>.</p>

       </li>

   <li><p>Build LLVM:</p>

 <pre class="doc_code">
 make
 </pre>
       </li>

   <li><p>Install LLVM (optional):</p>

 <pre class="doc_code">
 make install
 </pre>
       </li>

   <li><p>Make a build directory <tt>llvm-gcc-4.2-objects</tt> for llvm-gcc and make it the
       current directory:</p>

 <pre class="doc_code">
 cd ..
 mkdir llvm-gcc-4.2-objects
 cd llvm-gcc-4.2-objects
 </pre>
       </li>

   <li><p>Configure llvm-gcc (here it is configured to install into <tt>/usr/local</tt>).
       The <tt>--enable-checking</tt> flag turns on sanity checks inside the compiler.
       To turn off these checks (not recommended), replace <tt>--enable-checking</tt>
       with <tt>--disable-checking</tt>.
       Additional languages can be appended to the <tt>--enable-languages</tt> switch,
       for example <tt>--enable-languages=ada,c,c++</tt>.</p>

 <pre class="doc_code">
 ../llvm-gcc-4.2/configure --prefix=<b>/usr/local</b> --enable-languages=ada,c \
                           --enable-checking --enable-llvm=$PWD/../llvm-objects \
 			  --disable-bootstrap --disable-multilib
 </pre>

       <p>If you have a multi-compiler setup, then you can configure like this:</p>

 <pre class="doc_code">
 export CC=<b>PATH_TO_C_AND_ADA_COMPILER</b>
 export CXX=<b>PATH_TO_C++_COMPILER</b>
 ../llvm-gcc-4.2/configure --prefix=<b>/usr/local</b> --enable-languages=ada,c \
                           --enable-checking --enable-llvm=$PWD/../llvm-objects \
 			  --disable-bootstrap --disable-multilib
 </pre>
       </li>

   <li><p>Build and install the compiler:</p>

 <pre class="doc_code">
 make
 make install
 </pre>
       </li>
 </ol>

 </div>

 <!-- *********************************************************************** -->
 <h1><a name="fortran">Building the Fortran front-end</a></h1>
 <!-- *********************************************************************** -->

 <div class="doc_text">
 <p>To build with support for Fortran, follow the directions in the top-level
 <tt>README.LLVM</tt> file, adding ",fortran" to EXTRALANGS, for example:</p>

 <pre class="doc_code">
 EXTRALANGS=,fortran
 </pre>

 </div>

 <!-- *********************************************************************** -->
 <h1><a name="license">License Information</a></h1>
 <!-- *********************************************************************** -->

 <div class="doc_text">
 <p>
 The LLVM GCC frontend is licensed to you under the GNU General Public License
 and the GNU Lesser General Public License.  Please see the files COPYING and
 COPYING.LIB for more details.
 </p>

 <p>
 More information is <a href="FAQ.html#license">available in the FAQ</a>.
 </p>
 </div>

 <!-- *********************************************************************** -->

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	<html>
	<head>
	<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
	<link rel="stylesheet" href="llvm.css" type="text/css" media="screen">
	<title>Building the LLVM GCC Front-End</title>
	</head>
	<body>

	<div class="doc_title">
	Building the LLVM GCC Front-End
	</div>

	<ol>
	<li><a href="#instructions">Building llvm-gcc from Source</a></li>
	<li><a href="#ada">Building the Ada front-end</a></li>
	<li><a href="#fortran">Building the Fortran front-end</a></li>
	<li><a href="#license">License Information</a></li>
	</ol>

	<div class="doc_author">
	<p>Written by the LLVM Team</p>
	</div>

	<!-- *********************************************************************** -->
	<h1><a name="instructions">Building llvm-gcc from Source</a></h1>
	<!-- *********************************************************************** -->

	<div class="doc_text">

	<p>This section describes how to acquire and build llvm-gcc 4.2, which is based
	on the GCC 4.2.1 front-end. Supported languages are Ada, C, C++, Fortran,
	Objective-C and Objective-C++. Note that the instructions for building these
	front-ends are completely different (and much easier!) than those for building
	llvm-gcc3 in the past.</p>

	<ol>
	<li><p>Retrieve the appropriate llvm-gcc-4.2-<i>version</i>.source.tar.gz
	archive from the <a href="http://llvm.org/releases/">LLVM web
	site</a>.</p>

	<p>It is also possible to download the sources of the llvm-gcc front end
	from a read-only mirror using subversion. To check out the 4.2 code
	for first time use:</p>

	<div class="doc_code">
	<pre>
	svn co http://llvm.org/svn/llvm-project/llvm-gcc-4.2/trunk <i>dst-directory</i>
	</pre>
	</div>

	<p>After that, the code can be be updated in the destination directory
	using:</p>

	<div class="doc_code">
	<pre>svn update</pre>
	</div>

	<p>The mirror is brought up to date every evening.</p></li>

	<li>Follow the directions in the top-level <tt>README.LLVM</tt> file for
	up-to-date instructions on how to build llvm-gcc. See below for building
	with support for Ada or Fortran.
	</ol>

	</div>

	<!-- *********************************************************************** -->
	<h1><a name="ada">Building the Ada front-end</a></h1>
	<!-- *********************************************************************** -->

	<div class="doc_text">
	<p>Building with support for Ada amounts to following the directions in the
	top-level <tt>README.LLVM</tt> file, adding ",ada" to EXTRALANGS, for example:
	<tt>EXTRALANGS=,ada</tt></p>

	<p>There are some complications however:</p>

	<ol>
	<li><p>The only platform for which the Ada front-end is known to build is
	32 bit intel x86 running linux. It is unlikely to build for other
	systems without some work.</p></li>
	<li><p>The build requires having a compiler that supports Ada, C and C++.
	The Ada front-end is written in Ada so an Ada compiler is needed to
	build it. Compilers known to work with the
	<a href="http://llvm.org/releases/download.html">LLVM 2.7 release</a>
	are <a href="http://gcc.gnu.org/releases.html">gcc-4.2</a> and the
	2005, 2006 and 2007 versions of the
	<a href="http://libre.adacore.com/">GNAT GPL Edition</a>.
	<b>GNAT GPL 2008, gcc-4.3 and later will not work</b>.
	The LLVM parts of llvm-gcc are written in C++ so a C++ compiler is
	needed to build them. The rest of gcc is written in C.
	Some linux distributions provide a version of gcc that supports all
	three languages (the Ada part often comes as an add-on package to
	the rest of gcc). Otherwise it is possible to combine two versions
	of gcc, one that supports Ada and C (such as the
	<a href="http://libre.adacore.com/">2007 GNAT GPL Edition</a>)
	and another which supports C++, see below.</p></li>
	<li><p>Because the Ada front-end is experimental, it is wise to build the
	compiler with checking enabled. This causes it to run much slower, but
	helps catch mistakes in the compiler (please report any problems using
	<a href="http://llvm.org/bugs">LLVM bugzilla</a>).</p></li>
	<li><p>The Ada front-end <a href="http://llvm.org/PR2007">fails to
	bootstrap</a>, due to lack of LLVM support for
	<tt>setjmp</tt>/<tt>longjmp</tt> style exception handling (used
	internally by the compiler), so you must specify
	<tt>--disable-bootstrap</tt>.</p></li>
	</ol>

	<p>Supposing appropriate compilers are available, llvm-gcc with Ada support can
	be built on an x86-32 linux box using the following recipe:</p>

	<ol>
	<li><p>Download the <a href="http://llvm.org/releases/download.html">LLVM source</a>
	and unpack it:</p>

	<pre class="doc_code">
	wget http://llvm.org/releases/2.7/llvm-2.7.tgz
	tar xzf llvm-2.7.tgz
	mv llvm-2.7 llvm
	</pre>

	<p>or <a href="GettingStarted.html#checkout">check out the
	latest version from subversion</a>:</p>

	<pre class="doc_code">svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm</pre>

	</li>

	<li><p>Download the
	<a href="http://llvm.org/releases/download.html">llvm-gcc-4.2 source</a>
	and unpack it:</p>

	<pre class="doc_code">
	wget http://llvm.org/releases/2.7/llvm-gcc-4.2-2.7.source.tgz
	tar xzf llvm-gcc-4.2-2.7.source.tgz
	mv llvm-gcc-4.2-2.7.source llvm-gcc-4.2
	</pre>

	<p>or <a href="GettingStarted.html#checkout">check out the
	latest version from subversion</a>:</p>

	<pre class="doc_code">
	svn co http://llvm.org/svn/llvm-project/llvm-gcc-4.2/trunk llvm-gcc-4.2
	</pre>
	</li>

	<li><p>Make a build directory <tt>llvm-objects</tt> for llvm and make it the
	current directory:</p>

	<pre class="doc_code">
	mkdir llvm-objects
	cd llvm-objects
	</pre>
	</li>

	<li><p>Configure LLVM (here it is configured to install into <tt>/usr/local</tt>):</p>

	<pre class="doc_code">
	../llvm/configure --prefix=<b>/usr/local</b> --enable-optimized --enable-assertions
	</pre>

	<p>If you have a multi-compiler setup and the C++ compiler is not the
	default, then you can configure like this:</p>

	<pre class="doc_code">
	CXX=<b>PATH_TO_C++_COMPILER</b> ../llvm/configure --prefix=<b>/usr/local</b> --enable-optimized --enable-assertions
	</pre>

	<p>To compile without checking (not recommended), replace
	<tt>--enable-assertions</tt> with <tt>--disable-assertions</tt>.</p>

	</li>

	<li><p>Build LLVM:</p>

	<pre class="doc_code">
	make
	</pre>
	</li>

	<li><p>Install LLVM (optional):</p>

	<pre class="doc_code">
	make install
	</pre>
	</li>

	<li><p>Make a build directory <tt>llvm-gcc-4.2-objects</tt> for llvm-gcc and make it the
	current directory:</p>

	<pre class="doc_code">
	cd ..
	mkdir llvm-gcc-4.2-objects
	cd llvm-gcc-4.2-objects
	</pre>
	</li>

	<li><p>Configure llvm-gcc (here it is configured to install into <tt>/usr/local</tt>).
	The <tt>--enable-checking</tt> flag turns on sanity checks inside the compiler.
	To turn off these checks (not recommended), replace <tt>--enable-checking</tt>
	with <tt>--disable-checking</tt>.
	Additional languages can be appended to the <tt>--enable-languages</tt> switch,
	for example <tt>--enable-languages=ada,c,c++</tt>.</p>

	<pre class="doc_code">
	../llvm-gcc-4.2/configure --prefix=<b>/usr/local</b> --enable-languages=ada,c \
	--enable-checking --enable-llvm=$PWD/../llvm-objects \
	--disable-bootstrap --disable-multilib
	</pre>

	<p>If you have a multi-compiler setup, then you can configure like this:</p>

	<pre class="doc_code">
	export CC=<b>PATH_TO_C_AND_ADA_COMPILER</b>
	export CXX=<b>PATH_TO_C++_COMPILER</b>
	../llvm-gcc-4.2/configure --prefix=<b>/usr/local</b> --enable-languages=ada,c \
	--enable-checking --enable-llvm=$PWD/../llvm-objects \
	--disable-bootstrap --disable-multilib
	</pre>
	</li>

	<li><p>Build and install the compiler:</p>

	<pre class="doc_code">
	make
	make install
	</pre>
	</li>
	</ol>

	</div>

	<!-- *********************************************************************** -->
	<h1><a name="fortran">Building the Fortran front-end</a></h1>
	<!-- *********************************************************************** -->

	<div class="doc_text">
	<p>To build with support for Fortran, follow the directions in the top-level
	<tt>README.LLVM</tt> file, adding ",fortran" to EXTRALANGS, for example:</p>

	<pre class="doc_code">
	EXTRALANGS=,fortran
	</pre>

	</div>

	<!-- *********************************************************************** -->
	<h1><a name="license">License Information</a></h1>
	<!-- *********************************************************************** -->

	<div class="doc_text">
	<p>
	The LLVM GCC frontend is licensed to you under the GNU General Public License
	and the GNU Lesser General Public License. Please see the files COPYING and
	COPYING.LIB for more details.
	</p>

	<p>
	More information is <a href="FAQ.html#license">available in the FAQ</a>.
	</p>
	</div>

	<!-- *********************************************************************** -->

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