std::aligned_union
From cppreference.com
                    
                                        
                    
                    
                                                            
                    | Defined in header  <type_traits> | ||
| template< std::size_t Len, class... Types > struct aligned_union; | (since C++11) | |
Provides the member typedef type, which is a POD type of a size and alignment suitable for use as uninitialized storage for an object of any of the types listed in Types. The size of the storage is at least Len. std::aligned_union also determines the strictest (largest) alignment requirement among all Types and makes it available as the constant alignment_value.
If sizeof...(Types) == 0, the behavior is undefined.
| Contents | 
[edit] Member types
| Name | Definition | 
| type | the POD type suitable for storage of any type from Types | 
[edit] Helper types
| template< std::size_t Len, class... Types > using aligned_union_t = typename aligned_union<Len,Types...>::type; | (since C++14) | |
[edit] Member constants
| alignment_value [static] | the strictest alignment requirement of all Types(public static member constant) | 
[edit] Possible implementation
| #include <algorithm> template <std::size_t Len, class... Types> struct aligned_union { static constexpr std::size_t alignment_value = std::max({alignof(Types)...}); struct type { alignas(alignment_value) char _s[std::max({Len, sizeof(Types)...})]; }; }; | 
[edit] Example
| This section is incomplete Reason: no example | 
[edit] See also
| (C++11) | obtains the type's alignment requirements (class template) | 
| (C++11) | defines the type suitable for use as uninitialized storage for types of given size (class template) | 


