std::allocator::allocator
From cppreference.com
                    
                                        
                    
                    
                                                            
                    | allocator(); | (1) | |
| allocator( const allocator& other ); | (2) | |
| template< class U >  allocator( const allocator<U>& other ); | (3) | |
Constructs the default allocator. Since the default allocator is stateless, the constructors have no visible effect.
Parameters
| other | - | another allocator to construct with | 
Exceptions
| (none) | (until C++11) | 
| noexcept specification:   noexcept | (since C++11) |