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<!DOCTYPE html> <html> <!-- Created by GNU Texinfo 7.1, https://www.gnu.org/software/texinfo/ --> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <!-- This manual is for libffi, a portable foreign function interface library. Copyright © 2008-2024 Anthony Green and Red Hat, Inc. Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. --> <title>Simple Example (libffi: the portable foreign function interface library)</title> <meta name="description" content="Simple Example (libffi: the portable foreign function interface library)"> <meta name="keywords" content="Simple Example (libffi: the portable foreign function interface library)"> <meta name="resource-type" content="document"> <meta name="distribution" content="global"> <meta name="Generator" content="makeinfo"> <meta name="viewport" content="width=device-width,initial-scale=1"> <link href="index.html" rel="start" title="Top"> <link href="Index.html" rel="index" title="Index"> <link href="Using-libffi.html" rel="up" title="Using libffi"> <link href="Types.html" rel="next" title="Types"> <link href="The-Basics.html" rel="prev" title="The Basics"> <style type="text/css"> <!-- a.copiable-link {visibility: hidden; text-decoration: none; line-height: 0em} div.example {margin-left: 3.2em} span:hover a.copiable-link {visibility: visible} --> </style> </head> <body lang="en"> <div class="section-level-extent" id="Simple-Example"> <div class="nav-panel"> <p> Next: <a href="Types.html" accesskey="n" rel="next">Types</a>, Previous: <a href="The-Basics.html" accesskey="p" rel="prev">The Basics</a>, Up: <a href="Using-libffi.html" accesskey="u" rel="up">Using libffi</a> [<a href="Index.html" title="Index" rel="index">Index</a>]</p> </div> <hr> <h3 class="section" id="Simple-Example-1"><span>2.2 Simple Example<a class="copiable-link" href="#Simple-Example-1"> ¶</a></span></h3> <p>Here is a trivial example that calls <code class="code">puts</code> a few times. </p> <div class="example"> <pre class="example-preformatted">#include <stdio.h> #include <ffi.h> int main() { ffi_cif cif; ffi_type *args[1]; void *values[1]; char *s; ffi_arg rc; /* Initialize the argument info vectors */ args[0] = &ffi_type_pointer; values[0] = &s; /* Initialize the cif */ if (ffi_prep_cif(&cif, FFI_DEFAULT_ABI, 1, &ffi_type_sint, args) == FFI_OK) { s = "Hello World!"; ffi_call(&cif, puts, &rc, values); /* rc now holds the result of the call to puts */ /* values holds a pointer to the function's arg, so to call puts() again all we need to do is change the value of s */ s = "This is cool!"; ffi_call(&cif, puts, &rc, values); } return 0; } </pre></div> </div> </body> </html>