eval.c:266
void
rb_clear_cache_by_class(klass)
    VALUE klass;
{
    struct cache_entry *ent, *end;

    if (!ruby_running) return;
    ent = cache; end = ent + CACHE_SIZE;
    while (ent < end) {
	if (ent->klass == klass || ent->origin == klass) {
	    ent->mid = 0;
	}
	ent++;
    }
}
