elua/doc/en/tc_386.html

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<h3>Building GCC for i386</h3>
<p>At first, the idea of an i386 "cross" compiler under Linux seems
strange. After all, you're already running Linux on a i386 compatible
architecture. But the compiler is sometimes tied in mysterious ways
with the operating system it's running on (see for example <a href="http://wiki.osdev.org/GCC_Cross-Compiler">this page</a>
for some possible symptoms). And after all, you want to use Newlib, not
libc, and to customize your development environment as much as
possible. This tutorial will show you how to do that.</p>

<p><span class="warning">DISCLAIMER</span>: I'm by no means a specialist in the
GCC/newlib/binutils compilation process. I'm sure that there are better
ways to accomplish what I'm describing here, however I just wanted a
quick and dirty way to build a toolchain, I have no intention in
becoming too intimate with the build process. If you think that what I
did is wrong, inaccurate, or simply outrageously ugly, feel free to 
<a href="overview.html#contacts">contact us</a> and I'll make the necessary corrections. 
And of course, this tutorial comes without any guarantees whatsoever.</p>

<h2>Prerequisites</h2>
<p>To build your toolchain you'll need:</p>

<ul>
<li><b>GNU binutils</b>: as I'm writing this, the latest binutils version is 2.19.1, which
I'll be using in this tutorial. get it from <a  href="http://ftp.gnu.org/gnu/binutils/">here</a>.</li>
<li><b>GCC</b>:as I'm writing this, the latest GCC version is
4.3.3, which I'll be using for this tutorial. Download it from <a  href="http://gcc.gnu.org/mirrors.html">here</a> after choosing a suitable mirror.</li>
<li><b>Newlib</b>: as I'm writing this, the latest official Newlib version is 1.17.0, which I'll be using for this tutorial.
Download it from <a  href="ftp://sources.redhat.com/pub/newlib/index.html">here</a>.</li>
<li>The tutorial assumes that you're using bash as your shell. If you use
something else, you might need to adjust some shell-specific commands. </li></ul>

<p>You need some support programs/libraries in order to compile the toolchain. To install them:</p>
<pre><code>$ sudo apt-get install flex bison libgmp3-dev libmpfr-dev autoconf texinfo build-essential</code></pre>
<p>Next, decide where you want to install your toolchain. They
generally go in <i>/usr/local/</i>, so I'm going to assume
<i>/usr/local/cross-i686</i> for this tutorial. To save yourself some
typing, set this path into a shell variable:</p>
<pre><code>$ export TOOLPATH=/usr/local/cross-i686</code></pre>

<h2>Step 1: binutils</h2>

<p>This is the easiest step: unpack, configure, build.</p>

<pre><code>$ tar -xvjf binutils-2.19.1.tar.bz2
$ cd binutils-2.19.1
$ mkdir build
$ cd build
$ ../configure --target=i686-elf --prefix=$TOOLPATH --with-gnu-as --with-gnu-ld --disable-nls
$ make all
$ sudo make install
$ export PATH=${TOOLPATH}/bin:$PATH
$ cd ../..</code></pre>

<p>Now you have your i386 "binutils" (assembler, linker, disassembler ...) in your PATH. </p>

<h2>Step 2: basic GCC</h2>

<p>In this step we build a "basic" GCC (that is, a GCC without any
support libs, which we'll use in order to build all the libraries for
our target). Let's compile it (and note that the install step is 
a bit different from Newlib's):</p>

<pre><code>$ tar -xvjf gcc-4.3.3.tar.bz2
$ cd gcc-4.3.3
$ mkdir build
$ cd build
$ ../configure --target=i686-elf --prefix=$TOOLPATH --enable-languages="c,c++" --with-newlib --without-headers --disable-shared --with-gnu-as --with-gnu-ld
$ make all-gcc
$ sudo -s -H
# export PATH=/usr/local/cross-i686/bin:$PATH
# make install-gcc
# exit
$ cd ../..</code></pre>

<h2>Step 3: Newlib</h2>

<p>Once again, Newlib is as easy as unpack, configure, build. But I
wanted my library to be as small as possible (as opposed to as fast as
possible) and I only wanted to keep what's needed from it in the final
executable, so I added the "-ffunction-sections -fdata-sections" flags
to allow the linker to perform dead code stripping:</p>

<pre><code>$ tar -xvzf newlib-1.17.0.tar.gz
$ cd newlib-1.17.0
$ mkdir build
$ cd build
$ ../configure --target=i686-elf --prefix=$TOOLPATH --disable-newlib-supplied-syscalls --with-gnu-ld --with-gnu-as --disable-shared
$ make CFLAGS_FOR_TARGET="-ffunction-sections -fdata-sections -DPREFER_SIZE_OVER_SPEED -D__OPTIMIZE_SIZE__ -Os -fomit-frame-pointer -D__BUFSIZ__=256"
$ sudo -s -H
# export PATH=/usr/local/cross-i686/bin:$PATH
# make install
# exit 
$ cd ../..</code></pre>

<p>Some notes about the flags used in the above sequence:</p>

<ul>
  <li><code>--disable-newlib-supplied-syscalls</code>: this deserves a page of its own, but I won't cover it here. For an explanation, see for example 
  <a  href="http://openhardware.net/Embedded_ARM/NewLib_Stubs/">this page</a></li>
  <li><code>-DPREFER_SIZE_OVER_SPEED -D__OPTIMIZE_SIZE__</code>: compile Newlib for size, not for speed (these are Newlib specific).</li>
  <li><code>-Os -fomit-frame-pointer</code>: tell GCC to optimize for size, not for speed.</li>
  <li><code>-D__BUFSIZ__=256</code>: again Newlib specific, this is the buffer size allocated by default for files opened via fopen(). The default is 1024, which I find too much
   for <b>eLua</b>, so I'm using 256 here. Of course, you can change this value.</li></ul>

<h2>Step 4: full GCC</h2>

<p>Finally, in the last step of our tutorial, we complete the GCC
build. In this stage, a number of compiler support libraries are built
(most notably libgcc.a). Fortunately this is simpler that the Newlib
compilation step:</p>

<pre><code>$ cd gcc-4.3.3/build
$ make all
$ sudo make install
</code></pre>

<h2>Step 5: all done!</h2>

<p>Now you can finally enjoy your i386 toolchain, and compile <b>eLua</b> with
it :) After you do, you'll be able to boot <b>eLua</b> directly on your PC, as
described <a href="tut_bootpc.html">here</a>, but you won't need to download the ELF file from the <b>eLua</b> project page, since you just generated it using your own toolchain!
If you need further clarification, or if the above instructions didn't work for you, feel free to <a href="overview.html#contacts">contact us</a>.</p>
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