<?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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-->+
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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-6A37628A-C732-5765-9DC5-3AC691C2CD50" xml:lang="en"><title>Supporting+
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polymorphic interface DLLs with static interface DLLs</title><shortdesc>Explains how to support polymorphic interface DLLs with static+
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interface DLLs.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>+
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<p>In the previous sections showing how to use polymorphic interface DLLs,+
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the class declaration contains only pure virtual functions. In real applications,+
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the implementation of some of these functions could be the same in all implementation+
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DLLs, leading to duplication of code.</p>+
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<p>An abstract base class, intended for derivation in a polymorphic interface+
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DLL, can include functions declared as <codeph>IMPORT_C</codeph>. Such functions+
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must be implemented in a static interface DLL.</p>+
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<p>When a polymorphic interface DLL is loaded by <codeph>RLibrary::Load()</codeph>,+
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any static interface DLLs required by the polymorphic interface DLL are also+
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loaded.</p>+
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<p>If this technique is used, one function that can be usefully implemented+
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in the statically loaded DLL is an empty destructor.</p>+
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</conbody></concept>+
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