std::alignment_of (3) - Linux Man Pages

std::alignment_of: std::alignment_of

NAME

std::alignment_of - std::alignment_of

Synopsis


Defined in header <type_traits>
template< class T > (since C++11)
struct alignment_of;


Provides the member constant value equal to the alignment_requirement of the type T, as if obtained by an alignof expression. If T is an array type, returns the alignment requirements of the element type. If T is a reference type, returns the alignment requirements of the type referred to.
If alignof(T) is not a valid expression, the behavior is undefined.


Helper variable template


template< class T > (since C++17)
inline constexpr std::size_t alignment_of_v = alignment_of<T>::value;


Inherited from std::integral_constant

Member constants


value alignof(T)
         (public static member constant)
[static]

Member functions


                     converts the object to std::size_t, returns value
operator std::size_t (public member function)


operator() returns value
                     (public member function)
(C++14)

Member types


Type Definition
value_type std::size_t
type std::integral_constant<std::size_t, value>

Possible implementation


  template< class T >
  struct alignment_of : std::integral_constant<
                            std::size_t,
                            alignof(T)
                         > {};

Notes


This type trait predates the alignof_keyword, which can be used to obtain the same value with less verbosity.

Example


// Run this code


  #include <iostream>
  #include <type_traits>


  class A {};


  int main()
  {
      std::cout << std::alignment_of<A>::value << '\n';
      std::cout << std::alignment_of<int>() << '\n'; // alt syntax
      std::cout << std::alignment_of_v<double> << '\n'; // c++17 alt syntax
  }

Output:


  1
  4
  8

See also


alignof_operator queries alignment requirements of a type (since C++11)


aligned_storage defines the type suitable for use as uninitialized storage for types of given size
                 (class template)
(C++11)


aligned_union defines the type suitable for use as uninitialized storage for all given types
                 (class template)
(C++11)


max_align_t trivial type with alignment requirement as great as any other scalar type
                 (typedef)
(C++11)