<html><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968"><title>CL_UNWIND_PROTECT</title><link rel="stylesheet" href="ecl.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.75.2"><link rel="home" href="index.html" title="The ECL manual"><link rel="up" href="ch23s02.html" title="8.2. Embedding Reference"><link rel="prev" href="re37.html" title="CL_CATCH_ALL"><link rel="next" href="re39.html" title="cl_boot"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"><code class="function">CL_UNWIND_PROTECT</code></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="re37.html">Prev</a> </td><th width="60%" align="center">8.2. Embedding Reference</th><td width="20%" align="right"> <a accesskey="n" href="re39.html">Next</a></td></tr></table><hr></div><div class="refentry" title="CL_UNWIND_PROTECT"><a name="ref.embed.cl_unwind_protect"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p><code class="function">CL_UNWIND_PROTECT</code> — Create a protected region.</p></div><div class="refsynopsisdiv" title="C Macro"><h2>C Macro</h2><pre class="programlisting">
cl_env_ptr env = ecl_process_env();
CL_UNWIND_PROTECT_BEGIN(env) {
/*
* Code that is protected. Uncaught lisp conditions, THROW,
* signals such as SIGSEGV and SIGBUS may cause jump to
* this region.
*/
} CL_UNWIND_PROTECT_EXIT {
/*
* If the exception, lisp condition or other control transfer
* is caught, this code is executed. After this code, the
* process will jump to the original destination of the
* THROW, GOTO or other control statement that was interrupted.
*/
} CL_UNWIND_PROTECT_END
/*
* We only exit here if NO nonlocal jump was interrupted.
*/
</pre></div><div class="refsect1" title="Description"><a name="id671121"></a><h2>Description</h2><p>When embedding <span class="application">ECL</span> it is normally advisable to set up an
unwind-protect frame to avoid the embedded lisp code to perform arbitary
transfers of control. Furthermore, the unwind protect form will be
used in at least in the following ocasions:</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>In a normal program exit, caused by <code class="function">ext:quit</code>,
<span class="application">ECL</span> unwinds up to the outermost frame, which may be an <a class="xref" href="re37.html" title="CL_CATCH_ALL"><code class="function">CL_CATCH_ALL</code></a> or <a class="xref" href="re38.html" title="CL_UNWIND_PROTECT"><code class="function">CL_UNWIND_PROTECT</code></a> macro.</p></li></ul></div><p>Besides this, normal mechanisms for exit, such as
<code class="function">ext:quit</code>, and uncaught exceptions, such as serious
signals (<a class="xref" href="ch22s02.html#ext.signals.synchronous" title="7.2.1. Synchronous signals">Section 7.2.1</a>), are best handled using
unwind-protect blocks.</p></div><div class="refsect1" title="See also"><a name="id671189"></a><h2>See also</h2><p><a class="xref" href="re37.html" title="CL_CATCH_ALL"><code class="function">CL_CATCH_ALL</code></a></p></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="re37.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="ch23s02.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="re39.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top"><code class="function">CL_CATCH_ALL</code> </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> <code class="function">cl_boot</code></td></tr></table></div></body></html>
