Question

Could you ensure me, if all access specifiers (including inheritance) in struct are public ?

In other words: are those equal?

class C: public B, public A { public:
    C():A(1),B(2){}
    //...
};

and

struct C: B, A {
    C():A(1),B(2){}
    //...
};

Answer 1

From C++ standard, 11.2.2, page 208:

In the absence of an access-specifier for a base class, public is assumed when the derived class is declared struct and private is assumed when the class is declared class.

So yes, you are correct: when the derived class is a struct, it inherits other classes as public unless you specify otherwise.