author | Dominic Pinkman <dominic.pinkman@nokia.com> |
Fri, 11 Jun 2010 12:39:03 +0100 | |
changeset 8 | ae94777fff8f |
parent 0 | 89d6a7a84779 |
permissions | -rw-r--r-- |
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Initial contribution of Documentation_content according to Feature bug 1266 bug 1268 bug 1269 bug 1270 bug 1372 bug 1374 bug 1375 bug 1379 bug 1380 bug 1381 bug 1382 bug 1383 bug 1385
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<?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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Dominic Pinkman <Dominic.Pinkman@Nokia.com>
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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-FE138F1A-1F52-5E9A-8EB2-5A8945A9CF30" xml:lang="en"><title>Destructor |
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requirements</title><shortdesc>This document describes cleanup actions required for C type and |
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other classes.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody> |
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<p>For <codeph>C</codeph> type classes, cleanup invokes the destructor. For |
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other types of object, other actions may be required. </p> |
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<p>The destructor for <codeph>C</codeph> type classes must be coded to release |
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all resources owned by the object. By definition, cleanup may occur on <i>partially</i> constructed |
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objects: the destructor may not, therefore, assume that all conditions for |
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a fully-constructed object hold in these circumstances. A typical situation |
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to watch for is calling a member function on a pointer that is initialized |
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in the <codeph>ConstructL()</codeph>, as the pointer could be <codeph>NULL</codeph> in |
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failure cases.</p> |
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<p>Resources will usually be indicated by pointers or handles. It is important |
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that such pointers or handles are null when there is no resource allocated, |
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and that the destructor test for a non-null value before destroying them.</p> |
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<p>This behaviour is facilitated in <codeph>CBase</codeph> -derived classes, |
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because their memory is guaranteed to be initially set to binary zeroes when |
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they are first allocated.</p> |
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<p>Programmers must, however, take particular care with pointers which are |
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used for owned objects which are repeatedly allocated and de-allocated throughout |
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an object’s lifetime. When such owned objects are de-allocated, the pointer |
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should always immediately be set to null.</p> |
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<section id="GUID-DFAB4D8D-FD81-4754-9472-2BCFD8B90F9E"><title>See also</title> <p><xref href="GUID-7366AE99-DE25-5DE0-BF9A-58E7742DA952.dita">Advanced |
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Cleanup</xref>.</p> </section> |
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</conbody></concept> |