top_level_str_coll
ret = top_level_str_coll(str1, ((*ss2)->str));
ret = top_level_str_coll(((*ss1)->str), ((*ss2)->str));
return top_level_str_coll(((*ss1)->str), ((*ss2)->str));
int top_level_str_coll(const struct bwstring *, const struct bwstring *);
cmp = top_level_str_coll(s2, s1);