std::alignment_of
From cppreference.com
                    
                                        
                    
                    
                                                            
                    | Defined in header  <type_traits> | ||
| 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.
| Contents | 
[edit] Helper variable template
| template< class T > inline constexpr std::size_t alignment_of_v = alignment_of<T>::value; | (since C++17) | |
Inherited from std::integral_constant
Member constants
| value [static] | alignof(T) (public static member constant) | 
Member functions
| operator std::size_t | converts the object to std::size_t, returns value(public member function) | 
| operator() (C++14) | returns value(public member function) | 
Member types
| Type | Definition | 
| value_type | std::size_t | 
| type | std::integral_constant<std::size_t, value> | 
[edit] Possible implementation
| template< class T > struct alignment_of : std::integral_constant< std::size_t, alignof(T) > {}; | 
[edit] Notes
This type trait predates the alignof keyword, which can be used to obtain the same value with less verbosity.
[edit] 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
[edit] See also
| alignof operator | queries alignment requirements of a type (since C++11) | 
| (C++11) | defines the type suitable for use as uninitialized storage for types of given size (class template) | 
| (C++11) | defines the type suitable for use as uninitialized storage for all given types (class template) | 
| (C++11) | POD type with alignment requirement as great as any other scalar type (typedef) | 


