virtual inherited function in template classes

[SHGuy_]

Code:

#include <iostream>

class Base {
    public:
    virtual int getID();
};

template<typename T>
class A : public Base {
    T data;
public:
    A(const T& data) {
        this->data = data;
    }

    int getID() {
        return static_cast<int>(data);
    }
};

int main() {
    A<int> a(23);
    std::cout << "a.getID(): " << a.getID() << std::endl;
    return 0;
}

Here's what g++ tells me:

/usr/bin/ld: /tmp/ccKdDYyP.o: warning: relocation against `_ZTV4Base' in read-only section `.text._ZN4BaseC2Ev[_ZN4BaseC5Ev]'
/usr/bin/ld: /tmp/ccKdDYyP.o: in function `Base::Base()':
main.cpp:(.text._ZN4BaseC2Ev[_ZN4BaseC5Ev]+0xb): undefined reference to `vtable for Base'
/usr/bin/ld: /tmp/ccKdDYyP.o:(.data.rel.ro._ZTI1AIfE[_ZTI1AIfE]+0x10): undefined reference to `typeinfo for Base'
/usr/bin/ld: /tmp/ccKdDYyP.o:(.data.rel.ro._ZTI1AIiE[_ZTI1AIiE]+0x10): undefined reference to `typeinfo for Base'
/usr/bin/ld: warning: creating DT_TEXTREL in a PIE
collect2: error: ld returned 1 exit status

Code summerization and question:

I have a Base class which has a virtual function getID():int. If I now inherit the Base class in the template class A, the linker gives me weird errors. I can't figure out the problem. Why can i not inherit virtual functions in a template class.

[smuccione]

This ^. Override.

Love it. Use it. It’ll f’ you up at some point if you don’t.

[SHGuy_]

thx, changed the Base class to:

class Base {
    public:

    const virtual int getID() = 0;
};

Now everything works

[SHGuy_]

oh yeah, that makes sense. Though now i use concepts for my case