CODEWITHSUNDEEP
cfunctionpointersdelegatesunions
Chikage
Chikage

Reputation: 329

Declaring a Union Pointer as if it's a function

I have some code I can't quite understand.

typedef double Align;
union header{
    struct{
        union header *ptr;
        unsigned int size;
    }s;
    Align x;
};
typedef union header Header;

So, after creating this union it's used in a wierd way.

Header *morecore(unsigned);

This is then called like a normal function

Header *p;
p = morecore(nunits);

How exactly does this work? There is no code anywhere telling how this "function" works.

Upvotes: 2

Views: 78

Answers (2)

Marian
Marian

Reputation: 7472

Header *morecore(unsigned);

is a forward declaration of a function named morecore which takes 1 parameter of type unsigned and returns a pointer to Header. It is not related to the way how Header was defined. This function is defined somewhere in your code together with its body.

Upvotes: 1

Gopi
Gopi

Reputation: 19864

Header *morecore(unsigned);

This function returns a pointer of type Header. So the return value is assigned to the same type which is

Header *p = morecore(nunits);

So basically the function morecore() internally does some operation and returns a pointer and this return value is assigned to p.

Upvotes: 3

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