Pure-virtual method on base class causes linker error [duplicate]

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• What is an undefined reference/unresolved external symbol error and how do I fix it? 27 answers

I'm having inconsistent linker errors when trying to build my c++11 project in Visual Studio 2017.

I call them inconsistent primarily because they only happen now and then, forcing me to rebuild the entire project to get rid of them.

The equivalent pseudo-code is:

// Base.h
class Base
{
public:
    template <class Derived>
    static Derived* create()
    {
        Derived* d = new Derived();
        d->foo = 10;
        d->bar = 15;

        return d;
    }

    ~Base()
    {
        //
    }

    virtual void initialize() = 0;
    virtual void draw() = 0;
    virtual void update() = 0;

protected:
    Base()
    {
        //
    }
}

// Inheritor.h
class Inheritor : public Base
{
public:
    ~Inheritor()
    {
        //
    }

    virtual void initialize() override; // implemented on Inheritor.cpp
    virtual void draw() override; // implemented on Inheritor.cpp
    virtual void update() override; // implemented on Inheritor.cpp
}

The linker errors are related with the pure virtual methods in Base, but I don't understand what could be wrong, since I'm implementing everything in the Inheritor class.

Error   LNK2001 unresolved external symbol "public: virtual void __cdecl Inheritor::initialize(void)" (?initialize@Inheritor@@UEAAXXZ)  canvas.obj  1   
Error   LNK2001 unresolved external symbol "public: virtual void __cdecl Inheritor::draw()" (?draw@Inheritor@@UEAAXXZ)  canvas.obj  1   
Error   LNK2001 unresolved external symbol "public: virtual void __cdecl Inheritor::update(void)" (?update@Inheritor@@UEAAXXZ)  canvas.obj  1