std::pmr::null_memory_resource
From cppreference.com
                    
                                        
                    
                    
                                                            
                    |   Defined in header  <memory_resource>
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|   std::pmr::memory_resource* null_memory_resource() noexcept;  | 
(since C++17) | |
Returns a pointer to a memory_resource that doesn't perform any allocation.
Return value
Returns a pointer p to a static storage duration object of a type derived from std::pmr::memory_resource, with the following properties:
-  its 
allocate()function always throws std::bad_alloc; -  its 
deallocate()function has no effect; -  for any 
memory_resourcer,p->is_equal(r)returns&r == p. 
The same value is returned every time this function is called.