std::alignment_of (3) - Linux Manuals

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