Question

Are the attributes of a struct inherited in C++

eg:

struct A {
    int a;
    int b;
}__attribute__((__packed__));

struct B : A {
    list<int> l;
};

will the inherited part of struct B (struct A) inherit the packed attribute?

I cannot add an a attribute((packed)) to struct B without getting a compiler warning:

ignoring packed attribute because of unpacked non-POD field

So I know that the entire struct B will not be packed, which is fine in my use case, but I require the fields of struct A to be packed in struct B.

Answer 1

Yes, the members of A will be packed in struct B. It must be this way, otherwise it would break the whole point of inheritance. For example:

std::vector<A*> va;
A a;
B b;
va.push_back(&a);
vb.push_back(&b);

// loop through va and operate on the elements. All elements must have the same type and behave like pointers to A.