About default C struct values, what about this code?

Question

I\'m trying to create structs with default values. I don\'t know how to accomplish this because every code that I see, is about initialising, and I would it for the natural

Answer 1

I'm not sure quite sure what your problem is. The standard way of initialising structures in c is like this:

struct a_struct my_struct = {1, 2};

Or the more recent and safer:

struct a_struct my_struct = {.i1 = 1, .i2 = 2};

If there is more than one instance of a structure, or it needs to be re-initialised, it is useful to define a constant structure with default values then assign that.

typedef struct a_struct {
   int i1;
   int i2;
} sa;

static const sa default_sa = {.i1 = 1, .i2 = 2};

static sa sa1 = default_sa;
static sa sa2 = default_sa;

// obviously you can do it dynamically as well
void use_temp_sa(void)
{
     sa temp_sa = default_sa;
     temp_sa.i2 = 3;
     do_something_with(&temp_sa);
}

// And re-initialise
void reset_sa(sa *my_sa)
{
    *my_sa = default_sa;
}