Default values in a C Struct

Question

I have a data structure like this:

    struct foo {
        int id;
        int route;
        int backup_route;
        int current_route;
    }

and a

Answer 1

How about something like:

struct foo bar;
update(init_id(42, init_dont_care(&bar)));

with:

struct foo* init_dont_care(struct foo* bar) {
  bar->id = dont_care;
  bar->route = dont_care;
  bar->backup_route = dont_care;
  bar->current_route = dont_care;
  return bar;
}

and:

struct foo* init_id(int id, struct foo* bar) {
  bar->id = id;
  return bar;
}

and correspondingly:

struct foo* init_route(int route, struct foo* bar);
struct foo* init_backup_route(int backup_route, struct foo* bar);
struct foo* init_current_route(int current_route, struct foo* bar);

In C++, a similar pattern has a name which I don't remember just now.

EDIT: It's called the Named Parameter Idiom.