How to create a function inside a structure in a header file and implement this function in another c source file?

Question

Here I created a main.c

#include <iostream>
#include "Header.h"
struct person_t a;
int main()
{
    a.func(1,2);
}

And I have a header called "Header.h", I define a structure in this file

struct person_t {
    char name;
    unsigned age;
    int(*func)(int, int);
};

Then I implement int(*func)(int, int); in another c file called "Source.c"

#include "Header1.h"
struct person_t a;
int add2(int x, int y)
{
    return x + y;
};

a.func = &add2;

But it seems not work, does anyone who has any idea of this question?

Please describe the problem better than "not work". Provide the specific error or incorrect behaviour you observe. But for starters, `a.func = &add2;` is invalid C as non-initialiser assignment statements must be inside a function. — kaylum, Jul 31 '22 at 11:32
`struct person_t a;` in 2 different compilation units (files) are 2 different variables. `a.func = &add2;` can't exist outside of a function body. — tevemadar, Jul 31 '22 at 11:34
Thanks for your suggestions. I will describe more detail about what behaviour I observe. And finally I just solved my question — 0983, Jul 31 '22 at 12:11

Vlad from Moscow · Accepted Answer · 2022-07-31T11:50:58.427

0

You may not use statements outside a function like this

a.func = &add2;

Remove this statement and this declaration

struct person_t a;

from Source.c.

In the header place the function declaration

int add2(int x, int y);

And in the file with main write

int main()
{
    struct person_t a;
    a.func = add2;

    a.func(1,2);
}

edited Jul 31 '22 at 11:50

answered Jul 31 '22 at 11:38

Vlad from Moscow

1 Answers1