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<h4 class="subsection" id="Function-Locking-1"><span>11.10.6 Function Locking<a class="copiable-link" href="#Function-Locking-1"> ¶</a></span></h4>
<p>It is sometime desirable to lock a function into memory with the <code class="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 class="code">clear</code> does not remove this initialization.
</p>
<p>As an example,
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">function my_function ()
mlock ();
...
endfunction
</pre></div></div>
<p>prevents <code class="code">my_function</code> from being removed from memory after it is called,
even if <code class="code">clear</code> is called. It is possible to determine if a function is
locked into memory with the <code class="code">mislocked</code>, and to unlock a function with
<code class="code">munlock</code>, which the following code illustrates.
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">my_function ();
mislocked ("my_function")
⇒ ans = 1
munlock ("my_function");
mislocked ("my_function")
⇒ ans = 0
</pre></div></div>
<p>A common use of <code class="code">mlock</code> is to prevent persistent variables from being
removed from memory, as the following example shows:
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">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></div>
<p><code class="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 class="code">ignore_function_time_stamp</code> function.
</p>
<a class="anchor" id="XREFmlock"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-mlock"><span><strong class="def-name">mlock</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-mlock"> ¶</a></span></dt>
<dd><p>Lock the current function into memory so that it can’t be removed with
<code class="code">clear</code>.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFmunlock">munlock</a>, <a class="ref" href="#XREFmislocked">mislocked</a>, <a class="ref" href="Keywords.html#XREFpersistent">persistent</a>, <a class="ref" href="Status-of-Variables.html#XREFclear">clear</a>.
</p></dd></dl>
<a class="anchor" id="XREFmunlock"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-munlock"><span><strong class="def-name">munlock</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-munlock"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-munlock-1"><span><strong class="def-name">munlock</strong> <code class="def-code-arguments">(<var class="var">fcn</var>)</code><a class="copiable-link" href="#index-munlock-1"> ¶</a></span></dt>
<dd><p>Unlock the named function <var class="var">fcn</var> so that it may be removed from memory with
<code class="code">clear</code>.
</p>
<p>If no function is named then unlock the current function.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFmlock">mlock</a>, <a class="ref" href="#XREFmislocked">mislocked</a>, <a class="ref" href="Keywords.html#XREFpersistent">persistent</a>, <a class="ref" href="Status-of-Variables.html#XREFclear">clear</a>.
</p></dd></dl>
<a class="anchor" id="XREFmislocked"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-mislocked"><span><code class="def-type"><var class="var">tf</var> =</code> <strong class="def-name">mislocked</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-mislocked"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-mislocked-1"><span><code class="def-type"><var class="var">tf</var> =</code> <strong class="def-name">mislocked</strong> <code class="def-code-arguments">(<var class="var">fcn</var>)</code><a class="copiable-link" href="#index-mislocked-1"> ¶</a></span></dt>
<dd><p>Return true if the named function <var class="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 class="strong">See also:</strong> <a class="ref" href="#XREFmlock">mlock</a>, <a class="ref" href="#XREFmunlock">munlock</a>, <a class="ref" href="Keywords.html#XREFpersistent">persistent</a>, <a class="ref" href="Status-of-Variables.html#XREFclear">clear</a>.
</p></dd></dl>
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