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<div class="title">Porting JACK </div>  </div>
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<div class="textblock"><p>The <a class="el" href="index.html">JACK Audio Connection Kit</a> is designed to be portable to any system supporting the relevant POSIX and C language standards. It currently works with GNU/Linux and Mac OS X on several different processor architectures. This document describes the steps needed to port JACK to another platform, and the methods used to provide portability.</p>
<ul>
<li><a class="el" href="porting-guide.html#portrequirements">Requirements</a></li>
<li><a class="el" href="porting-guide.html#portoverview">Overview</a></li>
<li><a class="el" href="porting-guide.html#portopsys">Operating System Dependencies</a></li>
<li>portcpu</li>
<li><a class="el" href="porting-guide.html#portissues">Issues Not Addressed</a></li>
</ul>
<h1><a class="anchor" id="portrequirements"></a>
Requirements</h1>
<ul>
<li>Each platform should build directly from CVS or from a tarball using the GNU <code></code>./configure tools. Platform-specific toolsets can by used for development, but the GNU tools should at least work for basic distribution and configuration.</li>
<li>For long-term maintainability we want to minimize the use of conditional compilation in source files.</li>
<li>We should provide generic versions of all system-dependent headers, so platforms need only provide those they modify.</li>
<li>In some cases, operating system-specific information must be able to override processor-specific data.</li>
</ul>
<h1><a class="anchor" id="portoverview"></a>
Overview</h1>
<p>JACK relies on two types of platform-specific headers:</p>
<ul>
<li><a class="el" href="porting-guide.html#portopsys">Operating System Dependencies</a></li>
<li>portcpu</li>
</ul>
<p>OS-specific headers take precedence over CPU-specific headers.</p>
<p>The JACK <code>configure.host</code> script and its system-dependent header directories were adapted from the <code>libstdc++-v3</code> component of the GNU Compiler Collective, <a href="http://gcc.gnu.org">http://gcc.gnu.org</a>.</p>
<h1><a class="anchor" id="portlang"></a>
C Language Dependencies</h1>
<p>JACK is written to conform with C99, as defined in International Standard ISO/IEC 9899:1999. Because many existing compilers do not fully support this standard, some new features should be avoided for portablility reasons. For example, variables should not be declared in the middle of a compound statement, because many compilers still cannot handle that language extension.</p>
<h1><a class="anchor" id="portopsys"></a>
Operating System Dependencies</h1>
<p>JACK is written for a POSIX environment compliant with IEEE Std 1003.1-2001, ISO/IEC 9945:2003, including the POSIX Threads Extension (1003.1c-1995) and the Realtime and Realtime Threads feature groups. When some needed POSIX feature is missing on a platform, the preferred solution is to provide a substitute, as with the <code>fakepoll.c</code> implementation for Mac OS X.</p>
<p>Whenever possible, OS dependencies should be auto-detected by <code>configure</code>. Sometimes they can be isolated in OS-specific header files, found in subdirectories of <code>config/os</code> and referenced with a <code>&lt;sysdeps/xxx.h&gt;</code> name.</p>
<p>If conditional compilation must be used in mainline platform-independent code, avoid using the system name. Instead, <code>#define</code> a descriptive name in <code>&lt;config.h&gt;</code>, and test it like this:</p>
<div class="fragment"><div class="line">\#ifdef JACK_USE_MACH_THREADS</div>
<div class="line">        allocate_mach_serverport(engine, client);</div>
<div class="line">        client-&gt;running = FALSE;</div>
<div class="line">\#endif</div>
</div><!-- fragment --><p>Be sure to place any generic implementation alternative in the <code>#else</code> or use an <code>#ifndef</code>, so no other code needs to know your conditional labels.</p>
<h1><a class="anchor" id="portissues"></a>
Issues Not Addressed</h1>
<ul>
<li>Cross-compilation has not been tested, or even thought through in much detail. The <em>host</em> is the system on which JACK will run. This may differ from the <em>build</em> system doing the compilation. These are selected using the standard <code></code>./configure options <code>&ndash;host</code> and <code>&ndash;build</code>. Usually, <code></code>./config.guess can print the appropriate canonical name for any system on which it runs.</li>
<li>Platform-specific build tools like Apple's Project Builder are not well-supported. </li>
</ul>
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