each_pair

static VALUE
wmap_each(VALUE self)
{
    struct weakmap *w;
    rb_objspace_t *objspace = &rb_objspace;

    TypedData_Get_Struct(self, struct weakmap, &weakmap_type, w);
    st_foreach(w->wmap2obj, wmap_each_i, (st_data_t)objspace);
    return self;
}