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.
template< class T > inline constexpr std::size_t alignment_of_v = alignment_of<T>::value; | (since C++17) |
value
[static] | alignof(T) (public static member constant) |
operator std::size_t | converts the object to std::size_t , returns value (public member function) |
operator()
(C++14) | returns value (public member function) |
Type | Definition |
---|---|
value_type | std::size_t |
type | std::integral_constant<std::size_t, value> |
template< class T > struct alignment_of : std::integral_constant< std::size_t, alignof(T) > {}; |
This type trait predates the alignof keyword, which can be used to obtain the same value with less verbosity.
#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
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) | trivial type with alignment requirement as great as any other scalar type (typedef) |
© cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.
http://en.cppreference.com/w/cpp/types/alignment_of