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<title>Introduction (libffi: the portable foreign function interface library)</title>
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<div class="chapter" id="Introduction">
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Next: <a href="Using-libffi.html" accesskey="n" rel="next">Using libffi</a>, Previous: <a href="index.html" accesskey="p" rel="prev">libffi</a>, Up: <a href="index.html" accesskey="u" rel="up">libffi</a> [<a href="Index.html" title="Index" rel="index">Index</a>]</p>
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<hr>
<span id="What-is-libffi_003f"></span><h2 class="chapter">1 What is libffi?</h2>
<p>Compilers for high level languages generate code that follow certain
conventions. These conventions are necessary, in part, for separate
compilation to work. One such convention is the <em>calling
convention</em>. The calling convention is a set of assumptions made by
the compiler about where function arguments will be found on entry to
a function. A calling convention also specifies where the return
value for a function is found. The calling convention is also
sometimes called the <em>ABI</em> or <em>Application Binary Interface</em>.
<span id="index-calling-convention"></span>
<span id="index-ABI"></span>
<span id="index-Application-Binary-Interface"></span>
</p>
<p>Some programs may not know at the time of compilation what arguments
are to be passed to a function. For instance, an interpreter may be
told at run-time about the number and types of arguments used to call
a given function. <code>libffi</code> can be used in such programs to
provide a bridge from the interpreter program to compiled code.
</p>
<p>The <code>libffi</code> library provides a portable, high level programming
interface to various calling conventions. This allows a programmer to
call any function specified by a call interface description at run
time.
</p>
<p><acronym>FFI</acronym> stands for Foreign Function Interface. A foreign
function interface is the popular name for the interface that allows
code written in one language to call code written in another language.
The <code>libffi</code> library really only provides the lowest, machine
dependent layer of a fully featured foreign function interface. A
layer must exist above <code>libffi</code> that handles type conversions for
values passed between the two languages.
<span id="index-FFI"></span>
<span id="index-Foreign-Function-Interface"></span>
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