20 General utilities library [utilities]
namespace std::pmr {
class memory_resource;
bool operator==(const memory_resource& a, const memory_resource& b) noexcept;
template<class Tp> class polymorphic_allocator;
template<class T1, class T2>
bool operator==(const polymorphic_allocator<T1>& a,
const polymorphic_allocator<T2>& b) noexcept;
memory_resource* new_delete_resource() noexcept;
memory_resource* null_memory_resource() noexcept;
memory_resource* set_default_resource(memory_resource* r) noexcept;
memory_resource* get_default_resource() noexcept;
struct pool_options;
class synchronized_pool_resource;
class unsynchronized_pool_resource;
class monotonic_buffer_resource;
}