ObjectSpace::WeakMap#keys

static VALUE
wmap_keys(VALUE self)
{
    struct weakmap *w;
    struct wmap_iter_arg args;

    TypedData_Get_Struct(self, struct weakmap, &weakmap_type, w);
    args.objspace = &rb_objspace;
    args.value = rb_ary_new();
    st_foreach(w->wmap2obj, wmap_keys_i, (st_data_t)&args);
    return args.value;
}