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<div class="navheader"><table width="100%" summary="Navigation header"><tr><td width="20%" align="left"><a accesskey="p" href="kerl.html">Prev</a> </td><th width="60%" align="center"> </th><td width="20%" align="right"> <a accesskey="n" href="compat.html">Next</a></td></tr></table><hr /></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="cross_compiling"></a>Chapter 13. Cross compiling</h2></div></div></div><p>Erlang.mk supports cross-compiling. While the compiled
Erlang code is portable as-is, the C code is not and
releases need to use the correct runtime system for the
target environment.</p><p>There are therefore two steps that might require some
intervention: compiling and building the release. If
you do not have any C code you can just compile as you
would normally, however.</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="_compiling"></a>13.1. Compiling</h2></div></div></div><p>To cross-compile the C code you need a cross compiler. If you
were to target Windows from an Arch Linux machine you would
install the <a class="ulink" href="https://aur.archlinux.org/packages/mingw-w64-gcc/" target="_top">mingw-w64-gcc</a>
package. You would then need to define the <code class="literal">CC</code> environment
variable to point to this compiler instead of the default:</p><pre class="programlisting">CC=/usr/bin/x86_64-w64-mingw32-gcc</pre><p>Additionally, on Windows the shared libraries use a different
extension than on Linux, so it needs to be specified as well:</p><pre class="programlisting">C_SRC_OUTPUT_SHARED_EXTENSION=.dll</pre><p>These values can be added to the Makefile or given from the
command line, for example:</p><pre class="programlisting">$ CC=/usr/bin/x86_64-w64-mingw32-gcc C_SRC_OUTPUT_SHARED_EXTENSION=.dll make
DEPEND my_nif.d
ERLC my_nif.erl
APP my_nif
C my_nif.c
LD my_nif.dll
$ file priv/my_nif.dll
priv/my_nif.dll: PE32+ executable (DLL) (console) x86-64, for MS Windows</pre><p>You could also add this configuration to your Makefile hidden
behind a flag:</p><pre class="programlisting">ifdef WINDOWS_BUILD
CC = /usr/bin/x86_64-w64-mingw32-gcc
C_SRC_OUTPUT_SHARED_EXTENSION = .dll
endif</pre><p>And then just compile like this:</p><pre class="programlisting">$ make WINDOWS_BUILD=1</pre></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="_building_the_release"></a>13.2. Building the release</h2></div></div></div><p>For the release there are two options. You can either include
the correct runtime system directly in the release; or you
can not include the runtime system in the release and instead
let it use the one installed in the target environment.</p><p>To include the target runtime system, add the <code class="literal">include_erts</code>
tuple to your <span class="emphasis"><em>relx.config</em></span> file:</p><pre class="programlisting">{include_erts, "/path/to/alternate/erlang"}.</pre><p>If you were to target Windows for example, you could copy
the Erlang installation from the <span class="emphasis"><em>Program Files</em></span> directory
and then configure <span class="emphasis"><em>relx.config</em></span> like this:</p><pre class="programlisting">{include_erts, "/path/to/erl10.1"}.</pre><p>You need to make sure that the runtime system version you
will use is capable of running the compiled Erlang code
you used to build your project, otherwise it will fail
to run.</p><p>If you choose to not include the runtime system at all,
configure <span class="emphasis"><em>relx.config</em></span> as follow:</p><pre class="programlisting">{include_erts, false}.</pre><p>In that case the runtime system needs to be available
in the <code class="literal">$PATH</code> of the target environment.</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="kerl.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="code.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="compat.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top"> </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> </td></tr></table></div>
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