Symbian3/SDK/Source/GUID-14BBFDA8-7765-5939-9E47-36E299841F50.dita
author Dominic Pinkman <Dominic.Pinkman@Nokia.com>
Thu, 21 Jan 2010 18:18:20 +0000
changeset 0 89d6a7a84779
permissions -rw-r--r--
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
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
0
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
     1
<?xml version="1.0" encoding="utf-8"?>
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
     2
<!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. -->
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
     3
<!-- This component and the accompanying materials are made available under the terms of the License 
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
     4
"Eclipse Public License v1.0" which accompanies this distribution, 
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
     5
and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". -->
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
     6
<!-- Initial Contributors:
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
     7
    Nokia Corporation - initial contribution.
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
     8
Contributors: 
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
     9
-->
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    10
<!DOCTYPE concept
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    11
  PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    12
<concept id="GUID-14BBFDA8-7765-5939-9E47-36E299841F50" xml:lang="en"><title>How
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    13
to use the cleanup stack</title><shortdesc>This document describes how to use the cleanup stack when a function
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    14
leaves.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    15
<p>The cleanup stack is used as follows: </p>
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    16
<ol id="GUID-BAC73597-5165-55A6-B5E7-12FA156785DF">
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    17
<li id="GUID-9C056803-25F8-557C-B630-0B40D38EFABA"><p>Use <codeph>CleanupStack::PushL()</codeph> <b>  </b> to
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    18
push a pointer to the object onto the cleanup stack before any operation which
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    19
might leave is performed </p> </li>
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    20
<li id="GUID-F5F7946D-9E99-54B7-AF13-C76317296442"><p>Use <codeph>CleanupStack::Pop()</codeph> to
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    21
pop the pointer from the cleanup stack when all operations that might leave
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    22
have completed </p> </li>
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    23
</ol>
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    24
<p>If a function leaves, then part of leave processing is to pop <i>and destroy</i> all
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    25
objects on the cleanup stack. Thus, the cleanup stack may be used to prevent
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    26
objects becoming orphaned if a leave occurs. </p>
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    27
<codeblock id="GUID-4692E277-85DD-5178-B7AF-57539C9CA2E8" xml:space="preserve">void doExampleL()
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    28
 {
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    29
 // allocate with checking
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    30
 CExample* myExample = new (ELeave) CExample;
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    31
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    32
 // do something that cannot leave
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    33
 myExample-&gt;iInt = 5; // cannot leave: no protection needed
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    34
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    35
 // do something that can leave: use cleanup stack
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    36
 CleanupStack::PushL(myExample); // pointer on cleanup stack
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    37
 myExample-&gt;DoSomethingL(); // something that might leave
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    38
 CleanupStack::Pop(); // it didn't leave: pop the pointer
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    39
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    40
 // delete
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    41
 delete myExample;
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    42
 }</codeblock>
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    43
<section id="GUID-9DCA8E7D-9F8B-4597-9743-1793458DCB9B"><title>Notes</title> <ul>
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    44
<li id="GUID-AFBFF014-D03C-56A5-AA09-EB7BCF54A22A"><p>The cleanup stack is
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    45
necessary here because the <codeph>CExample</codeph> would be orphaned on
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    46
the heap if a leave occurred. This is because the <codeph>CExample</codeph> is
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    47
referred to only by an automatic pointer <codeph>myExample</codeph>, which
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    48
itself becomes orphaned on the stack when the leave occurs. If the <codeph>CExample</codeph> ’s
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    49
address had been stored in an object which was <i>not</i> orphaned by the
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    50
leave, then it would not be necessary to use the cleanup stack to ensure that
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    51
it is cleaned up correctly. </p> </li>
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    52
<li id="GUID-2B0103C5-991E-54AF-B21C-E68205212510"><p>The <codeph>CleanupStack::PushL()</codeph> operation
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    53
itself may leave because more memory may be needed for more cleanup stack
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    54
frames. It is guaranteed that the object is pushed to the stack before any
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    55
attempt is made to allocate more stack space. Thus, a failure of <codeph>CleanupStack::PushL()</codeph> will
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    56
cause the object that was being pushed to be cleaned up properly. </p> </li>
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    57
</ul> </section>
89d6a7a84779 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
Dominic Pinkman <Dominic.Pinkman@Nokia.com>
parents:
diff changeset
    58
</conbody></concept>