1 <?xml version="1.0" encoding="utf-8"?>

     2 <!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. -->

     3 <!-- This component and the accompanying materials are made available under the terms of the License 

     4 "Eclipse Public License v1.0" which accompanies this distribution, 

     5 and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". -->

     6 <!-- Initial Contributors:

     7     Nokia Corporation - initial contribution.

     8 Contributors: 

     9 -->

    10 <!DOCTYPE concept

    11   PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">

    12 <concept id="GUID-011D0974-CC37-5335-A8EB-7ECF4FC30F93" xml:lang="en"><title>Cleanup

    13 for heap arrays</title><shortdesc>C++ arrays are allocated on the heap and require their own particular

    14 cleanup.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

    15 <p>C++ arrays are allocated on the heap using <codeph>operator new[]</codeph>.

    16 The cleanup rules for such arrays are as follows:</p>

    17 <ul>

    18 <li id="GUID-41AA28AA-1D48-5B50-9065-A283CCAAD83F"><p>if it is not necessary

    19 to protect against leaves, such as when the array is a class member, or no

    20 leaves can occur in the lifetime of the array, then always delete the array

    21 using <codeph>operator delete[]</codeph> (not <codeph>operator delete</codeph>).</p> </li>

    22 <li id="GUID-B4EA79E7-EEDC-531D-90DB-7041F3650356"><p>if it is necessary to

    23 protect against leaves, push the array to the cleanup stack using the utility

    24 template function <codeph>CleanupArrayDeletePushL()</codeph>. This ensures

    25 that if a leave occurs, the array is deleted correctly using <codeph>operator

    26 delete[]</codeph>.</p> <p>Arrays should <i>not</i> be pushed to the cleanup

    27 stack using the standard <codeph>CleanupStack::PushL()</codeph>, as this will

    28 result in <codeph>operator delete</codeph> rather than <codeph>operator delete[]</codeph> being

    29 used for cleanup.</p> </li>

    30 </ul>

    31 <p><b>Note on compiler behaviour</b> </p>

    32 <p>Of the compilers used with Symbian platform, Metrowerks CodeWarrior is

    33 the most sensitive to the rules for array deletion. If an array is deleted

    34 with a simple <codeph>delete</codeph> rather than <codeph>delete[]</codeph>,

    35 then a USER 42 panic (invalid heap cell) can occur. </p>

    36 <p>This panic in fact occurs for arrays in which the class has either a constructor

    37 or a destructor. For such arrays, CodeWarrior reserves space at the start

    38 of the array storage to hold the number of elements in the array: this means

    39 the first heap cell is not the start of a deletable object. GCC and MSVC C++

    40 only reserve such extra space if the class has a destructor.</p>

    41 </conbody></concept>