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<!DOCTYPE concept
  PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
<concept id="GUID-18182059-859D-51CF-A940-D230D9F9CF8C" xml:lang="en"><title>How
to allocate and de-allocate cleanup stacks</title><shortdesc>This document describes when and how a cleanup stack should be
allocated and de-allocated.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>
<p>The main categories of programs (GUI applications and servers) both have
cleanup stacks created for them as part of their respective frameworks. Simple
console programs for test and demonstration purposes though require a cleanup
stack to be explicitly allocated. </p>
<p>Allocate the stack at the beginning of the thread as follows:</p>
<codeblock id="GUID-204BB8EA-016F-53CA-BB22-17B685BFF18A" xml:space="preserve">TheTrapCleanup=CTrapCleanup::New();</codeblock>
<p>De-allocate the cleanup stack at the end of the thread as follows:</p>
<codeblock id="GUID-C8A45849-E86C-5DA6-B1A5-88113B06C2B7" xml:space="preserve">delete TheTrapCleanup;</codeblock>
<section id="GUID-9E86AB70-D551-4356-9001-749FBE8B2DCE"><title>Notes</title> <ul>
<li id="GUID-37929EEE-F608-5754-9324-6731FEA5B1B2"><p>This explicit allocation
and de-allocation is necessary for threads which use cleanup processing. Threads
which do not use cleanup stack processing need not allocate a cleanup stack. </p> </li>
<li id="GUID-6B30E7F5-1D29-50EF-8896-0CD8400BBBCF"><p>Note that the cleanup
stack variable name (<codeph>TheTrapCleanup</codeph> in this case) is only
used to reference the stack when it needs to be destroyed. Therefore the user
is at liberty to give the stack any valid variable name. Multiple cleanup
stacks are supported: the system holds a stack of cleanup stacks, of which
the top item is the current cleanup stack. As such, when a new stack is created
it is pushed onto the stack of cleanup stacks, making it the current cleanup
stack. When it is destroyed, it is pushed off the stack of cleanup stacks
making the previously stacked cleanup stack the current one.</p> </li>
</ul> </section>
</conbody></concept>