Can I 'extend' a struct in C?

Question

typedef struct foo_s {
    int a;
} foo;

typedef struct bar_s {
    foo;
    int b;
} bar;

Essentially I want to do:

bar b;
b.a;
<         


        

Answer 1

There is a confusion between anonymous structures and unions with nameless field. The nameless field is a Microsoft Extension.

struct known {
    struct /* anonymous */ {
        int anonymous;
    };
    int known;
};

An anonymous struct or union is a struct or union without any tag name that is embedded within another struct or union. It does not need to have any field names either.

A nameless field is a Microsoft Extension that allows limited inheritance in C.

struct A {
    int a;
};

struct B {
    struct A: // nameless field
    int b;
};

Anonymous struct or union are not Nameless Fields, and Nameless Fields are not Anonymous, at least the way C11 standard defines it.