Implicitly deleted default constructor works in C++14

Question

I was doing some tests for some code that did not compile, and I discovered that this code:

struct A {
    A(int) {};
    virtual void foo() = 0;
};

struct B : public virtual A {
    virtual void bar() = 0;
};

struct C : public B {
    C() : A(1) {}
    virtual void foo() override {}
    virtual void bar() override {}
};

int main() {
    C c;
    return 0;
}

In C++11 fails to compile (on g++ 7.0.1) with ‘B::B()’ is implicitly deleted because the default definition would be ill-formed, while in C++14 compiles successfully.

I've tried to find out which new feature of C++14 allowed this to work, to no avail. The description in cppreference does not mention anything of the sort it seems.

Why can this code compile in C++14 but not in C++11?

Answer 1

Definitively it's a bug in gcc 7 because when I have checked out your code in a online compiler with gcc 7+, it has worked perfectly without any kind of problem.

So here I give you that IDE online where you can set your favorite compiler and try to do tests, if you want.

https://godbolt.org/

Sorry for I can't help you better but I couldn't reproduce your error.