Question

New to StackOverflow and new to C. I’m trying to take a struct as a parameter in a function ‘add_fields’, which adds the first two int fields ‘a’ and ‘b’ and puts the result in int field ‘c’. Not getting anything from the compiler, so obviously I’m doing something wrong. I just don’t know what. Any help would be appreciated.

    #include <stdio.h>

    struct add{
    int a;
    int b;
    int c;
    }

    void add_fields(struct add *d){
    d->c = a + b;

    }

    main(){

    struct add data;
    data.a = 1;
    data.b = 2;
    data.c = 0;
    add_fields(data);
    printf("%d + %d = %d", data.a, data.b, data.c);
}

Answer 1

You’re very close, but variables a and b don’t exist in that context, rather you need to access the fields via the pointer to struct d:

d->c = d->a + d->b;

Second, you need to pass a reference to the struct (since add_fields expects a pointer) when you call add_fields:

add_fields(&data);

The & indicates that you’re going to pass the address of the variable data rather than the value.