Compiler Error C2504
Visual Studio 2015
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The latest version of this topic can be found at Compiler Error C2504.
class' : base class undefined
The base class is declared but never defined. Possible causes:
Missing include file.
External base class not declared with extern.
The following sample generates C2504:
// C2504.cpp
// compile with: /c
class A;
class B : public A {}; // C2504
// OK
class C{};
class D : public C {};
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