std::nothrow_t
From cppreference.com
                    
                                        
                    
                    
                                                            
                    |   Defined in header <new>
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|   struct nothrow_t {};  | 
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std::nothrow_t is an empty class type used to disambiguate the overloads of throwing and non-throwing allocation functions.
[edit] See also
|    an object of type nothrow_t used to select an non-throwing allocation function   (constant)  | |
|    allocation functions   (function)  | |