Question

I have a structure and what I would like to do is to assign values to its members using a for loop. That way I do not have to use the members name. Because the structure is long and i do not want 20 lines of p_struct->member_name etc. What I have so far is below, but i am not sure if i am going in the right direction.
In header file:

typedef struct {
 int x;
 char ch;
  ...
  ...
}data;
data g_data;

in .c file…

data *p_data;
p_data = &(g_data.x)
for(i=0 till struct_elements) {
    *p_data = (some value);
    p_data++; //next member
}

Answer 1

This is not valid C. But what would be valid C is to make constant table of the types and offsets of each member, and use that in your loop:

struct struct_def {
    int typecode;
    size_t offset;
};

static const struct struct_def mystruct_def[] = {
    { TYPE_INT, offsetof(struct mystruct, x) },
    { TYPE_CHAR, offsetof(struct mystruct, y) },
    /* ... */
    { TYPE_NONE, 0 }
};

Then you could access the member x as *(int *)((char *)foo + mystruct_def[0].offset).

This is just an example; real world usage would probably be a bit more elaborate…