nm symbol T vs U [closed]

In a library foo, I have 2 member functions A & B in a base class, both overidden and both have full function definitions in Child.

    Base {
     virtual bool A() { return false; }
     virtual bool B() { return false; }
    }
    Child {
     bool A() override; 
     bool B() override;
    }

But strangely I am getting linker error "undefined" only for B. nm shows me:

    W Base::A
    T Child::A // why is this T
    W Base::B
    U Child::B // why is this U

Any ideas? And why would it show "T" for something that's not static.