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<a name="Function-Locking"></a>
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<p>
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<a name="Function-Locking-1"></a>
<h4 class="subsection">11.9.6 Function Locking</h4>
<p>It is sometime desirable to lock a function into memory with the <code>mlock</code>
function. This is typically used for dynamically linked functions in
oct-files or mex-files that contain some initialization, and it is desirable
that calling <code>clear</code> does not remove this initialization.
</p>
<p>As an example,
</p>
<div class="example">
<pre class="example">function my_function ()
mlock ();
…
endfunction
</pre></div>
<p>prevents <code>my_function</code> from being removed from memory after it is called,
even if <code>clear</code> is called. It is possible to determine if a function is
locked into memory with the <code>mislocked</code>, and to unlock a function with
<code>munlock</code>, which the following code illustrates.
</p>
<div class="example">
<pre class="example">my_function ();
mislocked ("my_function")
⇒ ans = 1
munlock ("my_function");
mislocked ("my_function")
⇒ ans = 0
</pre></div>
<p>A common use of <code>mlock</code> is to prevent persistent variables from being
removed from memory, as the following example shows:
</p>
<div class="example">
<pre class="example">function count_calls ()
mlock ();
persistent calls = 0;
printf ("count_calls() has been called %d times\n", ++calls);
endfunction
count_calls ();
-| count_calls() has been called 1 times
clear count_calls
count_calls ();
-| count_calls() has been called 2 times
</pre></div>
<p><code>mlock</code> might also be used to prevent changes to an m-file, such as in an
external editor, from having any effect in the current Octave session; A
similar effect can be had with the <code>ignore_function_time_stamp</code> function.
</p>
<a name="XREFmlock"></a><dl>
<dt><a name="index-mlock"></a><em></em> <strong>mlock</strong> <em>()</em></dt>
<dd><p>Lock the current function into memory so that it can’t be removed with
<code>clear</code>.
</p>
<p><strong>See also:</strong> <a href="#XREFmunlock">munlock</a>, <a href="#XREFmislocked">mislocked</a>, <a href="Persistent-Variables.html#XREFpersistent">persistent</a>, <a href="Status-of-Variables.html#XREFclear">clear</a>.
</p></dd></dl>
<a name="XREFmunlock"></a><dl>
<dt><a name="index-munlock"></a><em></em> <strong>munlock</strong> <em>()</em></dt>
<dt><a name="index-munlock-1"></a><em></em> <strong>munlock</strong> <em>(<var>fcn</var>)</em></dt>
<dd><p>Unlock the named function <var>fcn</var> so that it may be removed from memory with
<code>clear</code>.
</p>
<p>If no function is named then unlock the current function.
</p>
<p><strong>See also:</strong> <a href="#XREFmlock">mlock</a>, <a href="#XREFmislocked">mislocked</a>, <a href="Persistent-Variables.html#XREFpersistent">persistent</a>, <a href="Status-of-Variables.html#XREFclear">clear</a>.
</p></dd></dl>
<a name="XREFmislocked"></a><dl>
<dt><a name="index-mislocked"></a><em></em> <strong>mislocked</strong> <em>()</em></dt>
<dt><a name="index-mislocked-1"></a><em></em> <strong>mislocked</strong> <em>(<var>fcn</var>)</em></dt>
<dd><p>Return true if the named function <var>fcn</var> is locked in memory.
</p>
<p>If no function is named then return true if the current function is locked.
</p>
<p><strong>See also:</strong> <a href="#XREFmlock">mlock</a>, <a href="#XREFmunlock">munlock</a>, <a href="Persistent-Variables.html#XREFpersistent">persistent</a>, <a href="Status-of-Variables.html#XREFclear">clear</a>.
</p></dd></dl>
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