The following does not compile with gcc 4.9.2

class O {};

class D : public virtual O {
public:
    virtual float foo() const = 0;
};

class B : public D {
public:
    B(float, float) {}
};

class R : public B {
public:
    R() : B{1.f, 1.f} {}
    virtual float foo() const override { return 0.f; }
};

int main() {
    R r;
}

It says it cannot instantiate an object of abstract class B.
With Clang 3.6 it compiles.
See discussion here: http://stackoverflow.com/questions/29289857/base-class-with-pure-virtual-functions

If I use () instead of {} to create B, it compiles.
If B has only one parameter in the constructor instead of two, it compiles.