语法
class unsynchronized_pool_resource : public memory_resource {
unsynchronized_pool_resource(const pool_options& opts, memory_resource* upstream);
unsynchronized_pool_resource()
: unsynchronized_pool_resource(pool_options(), get_default_resource()) {}
explicit unsynchronized_pool_resource(memory_resource* upstream)
: unsynchronized_pool_resource(pool_options(), upstream) {}
explicit unsynchronized_pool_resource(const pool_options& opts)
: unsynchronized_pool_resource(opts, get_default_resource()) {}
unsynchronized_pool_resource(const unsynchronized_pool_resource&) = delete;
virtual ~unsynchronized_pool_resource();
unsynchronized_pool_resource&
operator=(const unsynchronized_pool_resource&) = delete;
void release();
memory_resource *upstream_resource() const;
pool_options options() const;
};