std::is_trivial

< cpp‎ | types

Defined in header `<type_traits>`
template< class T > struct is_trivial;		(since C++11)

If T is TrivialType (that is, a scalar type, a trivially copyable class with a trivial default constructor, or array of such type/class, possibly cv-qualified), provides the member constant value equal to true. For any other type, value is false.

The behavior is undefined if std::remove_all_extents_t<T> is an incomplete type and not (possibly cv-qualified) void.

The behavior of a program that adds specializations for is_trivial or is_trivial_v (since C++17) is undefined.

Template parameters

a type to check

Helper variable template

template< class T > inline constexpr bool is_trivial_v = is_trivial<T>::value;		(since C++17)

Inherited from std::integral_constant

Member constants

value

[static]

true if T is a trivial type , 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_type`	`bool`
`type`	std::integral_constant<bool, value>

Possible implementation

template< class T >
struct is_trivial : std::integral_constant< 
    bool,
    std::is_trivially_copyable<T>::value &&
    std::is_trivially_default_constructible<T>::value 
> {};

Example

#include <iostream>
#include <type_traits>
 
struct A {
    int m;
};
 
struct B {
    B() {}
};
 
int main() 
{
    std::cout << std::boolalpha;
    std::cout << std::is_trivial<A>::value << '\n';
    std::cout << std::is_trivial<B>::value << '\n';
}

Output:

true
false