Error: initializer element is not computable at load time

I have a function that takes a struct, and I'm trying to store its variables in array:

int detect_prm(Param prm) {
  int prm_arr[] = {prm.field1, prm.field2, prm.field3};

  return 0;
}

But with gcc -Wall -ansi -pedantic-errors -Werror I get the following error:

initializer element is not computable at load time

It looks fine to me, what's wrong?