struct and class and inheritance (c++)

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){}
    //...
};

You could have tested this yourself with a very small program. — Nobody moving away from SE, Jun 07 '12 at 10:38
Check this thread out about the differences between classes and structs in c++ http://stackoverflow.com/questions/92859/what-are-the-differences-between-struct-and-class-in-c — Benjamin Gruenbaum, Jun 07 '12 at 10:38
@Nobody: But then he'd rely on his compiler not having bugs :) — Daniel Daranas, Jun 07 '12 at 10:42

juanchopanza · Answer 1 · 2012-06-07T10:52:13.280

Yes, they all are public.

struct A : B {
  C c;
  void foo() const {}
}

is equivalent to

struct A : public B {
 public:
  C c;
  void foo() const {}
}

For members, it is specified in §11:

Members of a class defined with the keyword class are private by default. Members of a class defined with the keywords struct or union are public by default.

and for for base classes in §11.2:

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

where the references are to the C++11 standard.

score 2 · Accepted Answer · answered Jun 07 '12 at 10:44

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.

mloskot · Answer 3 · 2012-06-07T11:00:49.820

2

From the C++11 Standard (N3242 draft)

11.2 Accessibility of base classes and base class members

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

edited Jun 07 '12 at 11:00

answered Jun 07 '12 at 10:45

mloskot

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struct and class and inheritance (c++)

3 Answers3