Struct Inheritance in C

The closest you can get is the fairly common idiom:

typedef struct
{
    // base members

} Base;

typedef struct
{
    Base base;

    // derived members

} Derived;

As Derived starts with a copy of Base, you can do this:

Base *b = (Base *)d;

Where d is an instance of Derived. So they are kind of polymorphic. But having virtual methods is another challenge - to do that, you'd need to have the equivalent of a vtable pointer in Base, containing function pointers to functions that accept Base as their first argument (which you could name this).

By which point, you may as well use C++!

C has no explicit concept of inheritance, unlike C++. However, you can reuse a structure in another structure:

typedef struct {
    char name[NAMESIZE];
    char sex;
} Person;

typedef struct {
    Person person;
    char job[JOBSIZE];
} Employee;

typedef struct {
    Person person;
    char booktitle[TITLESIZE];
} LiteraryCharacter;

You can do the above mentioned

typedef struct
{
    // base members

} Base;

typedef struct
{
    Base base;

    // derived members

} Derived;

But if you want to avoid pointer casting, you can use pointers to a union of Base and Derived.

C is not an object-oriented language and hence has no inheritance.

You can simulate it, but you can't really inherit.

No, you cant. imo the best approach to OOP in C is using ADT.

No you cannot. C does not support the concept of inheritance.