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1 <?xml version="1.0" encoding="utf-8"?> |
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2 <!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. --> |
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3 <!-- This component and the accompanying materials are made available under the terms of the License |
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4 "Eclipse Public License v1.0" which accompanies this distribution, |
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5 and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". --> |
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6 <!-- Initial Contributors: |
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7 Nokia Corporation - initial contribution. |
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8 Contributors: |
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9 --> |
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10 <!DOCTYPE concept |
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11 PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd"> |
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12 <concept id="GUID-7A71CD0B-84C7-5A77-B573-C61F67C382DA" xml:lang="en"><title>Summary |
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13 of cleanup rules</title><shortdesc>This document states general rules for cleanup.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody> |
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14 <p>The general rules for cleanup during the lifetime of an object are:</p> |
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15 <ul> |
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16 <li id="GUID-AEE55F10-3FD5-5B09-B025-C5499DE7B312"><p>between the moment the |
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17 object is allocated, and the moment that a pointer to that object is stored |
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18 in a structure which would be accessible if a leave occurred, the object must |
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19 be pushed to the clean-up stack if a leave could possibly occur</p> </li> |
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20 <li id="GUID-B69DDE00-FE4C-582F-B5FA-0FA7684591F6"><p>when a pointer to the |
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21 object has been stored in an object which would be accessible if a leave occurred, |
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22 then the object should be popped from the cleanup stack before a leave could |
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23 possibly occur: normally, the object is popped first, and then the pointer |
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24 is stored</p> </li> |
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25 <li id="GUID-D8D6B31E-0B9F-56C6-B9B0-2197549E78FC"><p>an object is accessible |
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26 if a leave occurs, if either it is pushed to the cleanup stack, or there is |
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27 a reference to it from another object which would be accessible if a leave |
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28 occurred, or there is a reference to it from a stack frame which would not |
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29 be affected when a leave occurs (because of an appropriately-placed <codeph>TRAP</codeph>), |
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30 or there is a reference to it from a global variable</p> </li> |
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31 <li id="GUID-4F508BDB-59D1-52EA-84C2-CABE3E9339EC"><p>it should never be possible |
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32 to clean up an object more than once, if a leave occurred</p> </li> |
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33 </ul> |
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34 <p>In practice, this means that an object must be referred to either by a |
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35 cleanup stack frame, or by a reference from another object. More rarely, the |
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36 object may be referred to by a stack frame which cannot be unwound during |
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37 the lifetime of that object, because of an appropriate <codeph>TRAP</codeph>. |
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38 More rarely still, the object may be referred to by a global variable.</p> |
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39 </conbody></concept> |