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<title>Introduction (libffi: the portable foreign function interface library)</title>

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<h2 class="chapter" id="What-is-libffi_003f"><span>1 What is libffi?<a class="copiable-link" href="#What-is-libffi_003f"> &para;</a></span></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 class="dfn">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 class="dfn">ABI</em> or <em class="dfn">Application Binary Interface</em>.
<a class="index-entry-id" id="index-calling-convention"></a>
<a class="index-entry-id" id="index-ABI"></a>
<a class="index-entry-id" id="index-Application-Binary-Interface"></a>
</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 class="code">libffi</code> can be used in such programs to
provide a bridge from the interpreter program to compiled code.
</p>
<p>The <code class="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><abbr class="acronym">FFI</abbr> 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 class="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 class="code">libffi</code> that handles type conversions for
values passed between the two languages.
<a class="index-entry-id" id="index-FFI"></a>
<a class="index-entry-id" id="index-Foreign-Function-Interface"></a>
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