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POAmbiguity in multiple inheritance of interfaces in C++
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  1. POAmbiguity in multiple inheritance of interfaces in C++
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    copied!<p>I made a test code as following:</p> <pre class="lang-C++ prettyprint-override"><code>#include &lt;iostream&gt; using namespace std; #ifndef interface #define interface struct #endif interface Base { virtual void funcBase() = 0; }; interface Derived1 : public Base { virtual void funcDerived1() = 0; }; interface Derived2 : public Base { virtual void funcDerived2() = 0; }; interface DDerived : public Derived1, public Derived2 { virtual void funcDDerived() = 0; }; class Implementation : public DDerived { public: void funcBase() { cout &lt;&lt; "base" &lt;&lt; endl; } void funcDerived1() { cout &lt;&lt; "derived1" &lt;&lt; endl; } void funcDerived2() { cout &lt;&lt; "derived2" &lt;&lt; endl; } void funcDDerived() { cout &lt;&lt; "dderived" &lt;&lt; endl; } }; int main() { DDerived *pObject = new Implementation; pObject-&gt;funcBase(); return 0; } </code></pre> <p>The reason I wrote this code is to test if the function funcBase() can be called in an instance of DDerived or not. My C++ complier (Visual Studio 2010) gave me a compile error message when I tried to compile this code. In my opinion, there is no problem in this code because it is certain that the function <code>funcBase()</code> will be implemented (thus overriden) in some derived class of the interface <code>DDerived</code>, because it is pure virtual. In other words, any pointer variable of type <code>Implementation *</code> should be associated with an instance of a class deriving Implentation and overriding the function <code>funcBase()</code>. </p> <p>My question is, why the compiler give me such an error message? Why the C++ syntax is defined like that; i.e., to treat this case as an error? How can I make the code runs? I want to allow multiple inheritance of interfaces. Of course, if I use "virtual public" or re-declare the function <code>funcBase()</code> in <code>Implementation</code> like </p> <pre class="lang-C++ prettyprint-override"><code>interface DDerived : public Derived1, public Derived2 { virtual void funcBase() = 0; virtual void funcDDerived() = 0; }; </code></pre> <p>then everything runs with no problem. </p> <p>But I don't want to do that and looking for more convenient method, because virtual inheritance may degrade the performance, and re-declaration is so tedious to do if inheritance relations of classes are very complex. Is there any methods to enable multiple inheritance of interfaces in C++ other than using virtual inheritance?</p>
 

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