From cppreference.com
template<classT>structis_void;(since C++11)std::is_void is a
.
Checks whether T is a void type. Provides the member constant value that is equal to true, if T is the type void, constvoid, volatilevoid, or constvolatilevoid. Otherwise, value is equal to false.
If the program adds specializations for std::is_void or std::is_void_v, the behavior is undefined.
Template parameters
T - a type to check Helper variable template
template<classT>constexprboolis_void_v=is_void<T>::value;(since C++17)Inherited from
Member constants
value
[static]
true if T is the type void (possibly cv-qualified), false otherwise
(public static member constant)Member functions
operator bool
converts the object to bool, returns value
(public member function)operator()
(C++14)
returns value
(public member function)Member types
Type Definition value_typebooltypestd::integral_constant<bool,value>Possible implementation
template<classT>structis_void:std::is_same<void,typenamestd::remove_cv<T>::type>{};Example
Run this code
#include<type_traits>voidfoo();static_assert(std::is_void_v<void>==trueandstd::is_void_v<constvoid>==trueandstd::is_void_v<volatilevoid>==trueandstd::is_void_v<void*>==falseandstd::is_void_v<int>==falseandstd::is_void_v<decltype(foo)>==falseandstd::is_void_v<std::is_void<void>>==false);intmain(){}See also
(C++11)
checks if a type is an array type
(class template)
(C++11)
checks if a type is a pointer type
(class template)
(C++11)
checks if a type is an enumeration type
(class template)
(C++11)
checks if a type is a union type
(class template)
(C++11)
checks if a type is a non-union class type
(class template)
(C++11)
checks if a type is a function type
(class template)
(C++11)
checks if a type is an object type
(class template)
(C++26)
checks if reflected type is void
(function)