std::alignment_of - cppreference.com (original) (raw)

| | | | | ------------------------------------------ | | ------------- | | template< class T > struct alignment_of; | | (since C++11) |

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.

If the program adds specializations for std::alignment_of or std::alignment_of_v(since C++17), the behavior is undefined.

Contents

• 1 Helper variable template
• 2 Inherited from std::integral_constant
  • 2.1 Member constants
  • 2.2 Member functions
  • 2.3 Member types
  • 2.4 Possible implementation
  • 2.5 Notes
  • 2.6 Example
  • 2.7 See also

[edit] Helper variable template

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

Inherited from std::integral_constant

Member constants

| | alignof(T) (public static member constant) | | --------------------------------------------- |

Member functions

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

Member types

[edit] Possible implementation

[edit] Notes

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

[edit] Example

#include #include #include   struct A {}; struct B { std::int8_t p; std::int16_t q; };   int main() { std::cout << std::alignment_of::value << ' '; std::cout << std::alignment_of::value << ' '; std::cout << std::alignment_of() << ' '; // alt syntax std::cout << std::alignment_of_v << '\n'; // c++17 alt syntax }

Possible output:

[edit] See also