std::aligned_union

 

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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.

Member types

Name	Definition
type	the POD type suitable for storage of any type from Types

Helper types

template< std::size_t Len, class... Types > using aligned_union_t = typename aligned_union<Len,Types...>::type;		(since C++14)

Member constants

alignment_value [static]

the strictest alignment requirement of all Types (public static member constant)

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)...})]; }; };

See also

alignment_of (C++11)	obtains the type's alignment requirements (class template)
aligned_storage (C++11)	defines the type suitable for use as uninitialized storage for types of given size (class template)