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

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

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

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

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

<!-- Initial Contributors:

    Nokia Corporation - initial contribution.

Contributors: 

-->

<!DOCTYPE concept

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

<concept id="GUID-911CD800-2D1B-5D7B-A67C-66E01F91062C" xml:lang="en"><title>Heaps</title><shortdesc>The main thread of a process has a memory chunk that contains the

thread's heap. A program's request for memory is allocated from this heap.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

<p>Each thread has a chunk which contains that thread's program stack. For

the main thread of a process, this chunk also contains the thread's heap.

A program's request for memory is allocated from this heap. For example, a

code fragment such as: </p>

<codeblock id="GUID-ED3A8BC9-7601-5035-B422-ED80E5504867" xml:space="preserve">CArrayFixFlat&lt;...&gt;* fixflat;

...

fixflat = new (ELeave) CArrayFixFlat&lt;...&gt;(3);</codeblock>

<p>causes a portion of memory to be allocated from the heap and its address

returned to the caller. Memory from the heap must be explicitly requested

and, importantly, explicitly freed by the program. </p>

<p>If a process creates additional threads, then a new chunk is created for

each new thread. Each chunk contains the thread's stack; if a new thread is

not sharing an existing heap, then the chunk also contains a new heap. </p>

<p>When a new thread is created, either: </p>

<ul>

<li id="GUID-C915A4D8-70D9-55B4-A16F-9729B1F8D94B"><p>a new heap is created

for it </p> </li>

<li id="GUID-E72B8DF5-CB52-5333-9D3E-EFDBAFE6CB59"><p>it uses the creating

thread's heap </p> </li>

<li id="GUID-20C6F186-6EF6-511E-9291-3273CA930B5D"><p>it uses an explicitly

referenced heap. </p> </li>

</ul>

<p>A thread gets the handle to its heap by calling <xref href="GUID-C197C9A7-EA05-3F24-9854-542E984C612D.dita#GUID-C197C9A7-EA05-3F24-9854-542E984C612D/GUID-42AC433D-1C9C-3AC6-8640-EB1A7BA876B5"><apiname>User::Heap()</apiname></xref>. </p>

<p>See <xref href="GUID-D557CC2C-C045-5818-B2F7-9BD8BC39257D.dita">Address Space

and Process</xref> for more background on chunks and heaps.</p>