Initializing struct within a function then storing its address

Question

Hi I have a struct like this

struct small_struct {
  int a;
  int b;
}

struct big_struct {
  struct *small_struct child;
}

I want to pass the pointer of big_struct as a parameter into a function in which child is initialized.

static int my_function(struct big_struct* s) {
  if (certain_condition)
    s->child = &(struct small_struct) {
      .a = 1;
      .b = 2;
    }
}

However, when I do this and my_function is finished, the fields in s->child are often changed outside of the my_function. Would there be a way to keep a and b values as it was initialized inside my_function?

Thank you!