C structs don't define types?

Question

I\'ve just started learning C with a professional Java background and some (if no too much) C++ knowledge, and I was astonished that this doesn\'t work in C:

str         


        

Answer 1

In C there is no confusion between

struct Point {
    int x;
    int y;
};

and

union Point {
    int x;
    int y;
};

which are two different types called struct Point and union Point respectively.

The C99 standard section 6.7.2.1 states:

6 Structure and union specifiers have the same form. The keywords struct and union indicate that the type being specified is, respectively, a structure type or a union type.

7 The presence of a struct-declaration-list in a struct-or-union-specifier declares a new type, within a translation unit.

So it most unequivocally declares a type. The syntax for type names in C is given in sections 6.7.6 and includes the specifier-qualifier-list from 6.7.2, which takes the form of struct-or-union identifier.

Does this code works in C99? Or is this a "C++ thing"?

No, C99 does not decide to promote structure types over enum types and union types with the same name. It is a "C++ thing", as struct and classes are mostly the same thing in C++, and classes are important to C++.