<?xml version="1.0" encoding="utf-8"?>+
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<!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. -->+
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<!-- This component and the accompanying materials are made available under the terms of the License +
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"Eclipse Public License v1.0" which accompanies this distribution, +
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and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". -->+
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<!-- Initial Contributors:+
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    Nokia Corporation - initial contribution.+
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Contributors: +
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-->+
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<!DOCTYPE concept+
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  PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">+
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<concept id="GUID-011D0974-CC37-5335-A8EB-7ECF4FC30F93" xml:lang="en"><title>Cleanup+
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for heap arrays</title><shortdesc>C++ arrays are allocated on the heap and require their own particular+
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cleanup.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>+
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<p>C++ arrays are allocated on the heap using <codeph>operator new[]</codeph>.+
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The cleanup rules for such arrays are as follows:</p>+
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<ul>+
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<li id="GUID-41AA28AA-1D48-5B50-9065-A283CCAAD83F"><p>if it is not necessary+
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to protect against leaves, such as when the array is a class member, or no+
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leaves can occur in the lifetime of the array, then always delete the array+
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using <codeph>operator delete[]</codeph> (not <codeph>operator delete</codeph>).</p> </li>+
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<li id="GUID-B4EA79E7-EEDC-531D-90DB-7041F3650356"><p>if it is necessary to+
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protect against leaves, push the array to the cleanup stack using the utility+
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template function <codeph>CleanupArrayDeletePushL()</codeph>. This ensures+
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that if a leave occurs, the array is deleted correctly using <codeph>operator+
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delete[]</codeph>.</p> <p>Arrays should <i>not</i> be pushed to the cleanup+
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stack using the standard <codeph>CleanupStack::PushL()</codeph>, as this will+
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result in <codeph>operator delete</codeph> rather than <codeph>operator delete[]</codeph> being+
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used for cleanup.</p> </li>+
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</ul>+
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<p><b>Note on compiler behaviour</b> </p>+
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<p>Of the compilers used with Symbian platform, Metrowerks CodeWarrior is+
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the most sensitive to the rules for array deletion. If an array is deleted+
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with a simple <codeph>delete</codeph> rather than <codeph>delete[]</codeph>,+
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then a USER 42 panic (invalid heap cell) can occur. </p>+
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<p>This panic in fact occurs for arrays in which the class has either a constructor+
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or a destructor. For such arrays, CodeWarrior reserves space at the start+
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of the array storage to hold the number of elements in the array: this means+
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the first heap cell is not the start of a deletable object. GCC and MSVC C+++
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only reserve such extra space if the class has a destructor.</p>+
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</conbody></concept>+
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