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<concept id="GUID-6A37628A-C732-5765-9DC5-3AC691C2CD50" xml:lang="en"><title>Supporting

polymorphic interface DLLs with static interface DLLs</title><shortdesc>Explains how to support polymorphic interface DLLs with static

interface DLLs.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

<p>In the previous sections showing how to use polymorphic interface DLLs,

the class declaration contains only pure virtual functions. In real applications,

the implementation of some of these functions could be the same in all implementation

DLLs, leading to duplication of code.</p>

<p>An abstract base class, intended for derivation in a polymorphic interface

DLL, can include functions declared as <codeph>IMPORT_C</codeph>. Such functions

must be implemented in a static interface DLL.</p>

<p>When a polymorphic interface DLL is loaded by <codeph>RLibrary::Load()</codeph>,

any static interface DLLs required by the polymorphic interface DLL are also

loaded.</p>

<p>If this technique is used, one function that can be usefully implemented

in the statically loaded DLL is an empty destructor.</p>