std::pmr::memory_resource::do_is_equal (3) - Linux Manuals
virtual bool do_is_equal(const std::pmr::memory_resource& other) const noexcept = 0; (since C++17)
Compares *this for equality with other.
Two memory_resources compare equal if and only if memory allocated from one memory_resource can be deallocated from the other and vice versa.
The most-derived type of other may not match the most derived type of *this. A derived class implementation therefore must typically check whether the most derived types of *this and other match using dynamic_cast, and immediately return false if the cast fails.
is_equal (public member function)