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<h1 class="title">FFI</h1>
<p><small>There is a new edition of the book and this is an old link.</small></p>
<blockquote>
<p>Sometimes, your Rust code may need to interact with code written in another language.
To do this, Rust has a keyword, <code>extern</code>, that facilitates creating and using a <em>Foreign Function Interface</em> (FFI).</p>
</blockquote>
<pre class="rust rust-example-rendered">
<span class="kw">extern</span> <span class="string">"C"</span> {
<span class="kw">fn</span> <span class="ident">abs</span>(<span class="ident">input</span>: <span class="ident">i32</span>) <span class="op">-></span> <span class="ident">i32</span>;
}
<span class="kw">fn</span> <span class="ident">main</span>() {
<span class="kw">unsafe</span> {
<span class="macro">println</span><span class="macro">!</span>(<span class="string">"Absolute value of -3 according to C: {}"</span>, <span class="ident">abs</span>(<span class="op">-</span><span class="number">3</span>));
}
}<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Aextern%20%22C%22%20%7B%0A%20%20%20%20fn%20abs(input%3A%20i32)%20-%3E%20i32%3B%0A%7D%0A%0Afn%20main()%20%7B%0A%20%20%20%20unsafe%20%7B%0A%20%20%20%20%20%20%20%20println!(%22Absolute%20value%20of%20-3%20according%20to%20C%3A%20%7B%7D%22%2C%20abs(-3))%3B%0A%20%20%20%20%7D%0A%7D">Run</a></pre>
<hr />
<p>Here are the relevant sections in the new and old books:</p>
<ul>
<li><strong><a href="second-edition/ch19-01-unsafe-rust.html#using-extern-functions-to-call-external-code">In the second edition: Ch 19.01 — Unsafe Rust, section <code>extern</code> functions</a></strong></li>
<li><small><a href="first-edition/ffi.html">In the first edition: Ch 4.9 — FFI</a></small></li>
</ul>
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