C++

Reference

<type_traits>

class template
<type_traits>

std::is_trivial

template <class T> struct is_trivial;
Is trivial type

Trait class that identifies whether T is a trivial type.

A trivial type is a type whose storage is contiguous (trivially copyable) and which only supports static default initialization (trivially default constructible), either cv-qualified or not. It includes scalar types, trivial classes and arrays of any such types.

A trivial class is a class (defined with class, struct or union) that is both trivially default constructible and trivially copyable, which implies that:
  • uses the implicitly defined default, copy and move constructors, copy and move assignments, and destructor.
  • has no virtual members.
  • has no non-static data members with brace- or equal- initializers.
  • its base class and non-static data members (if any) are themselves also trivial types.

is_trivial inherits from integral_constant as being either true_type or false_type, depending on whether T is a trivial type.

Template parameters

T
A complete type, or void (possible cv-qualified), or an array of unknown bound of a complete element type.

Member types

Inherited from integral_constant:
member typedefinition
value_typebool
typeeither true_type or false_type

Member constants

Inherited from integral_constant:
member constantdefinition
valueeither true or false

Member functions

Inherited from integral_constant:
operator bool
Returns value (public member function)

Example

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// is_trivial example
#include <iostream>
#include <type_traits>

class A {};
class B { B() {} };
class C : B {};
class D { virtual void fn() {} };

int main() {
  std::cout << std::boolalpha;
  std::cout << "is_trivial:" << std::endl;
  std::cout << "int: " << std::is_trivial<int>::value << std::endl;
  std::cout << "A: " << std::is_trivial<A>::value << std::endl;
  std::cout << "B: " << std::is_trivial<B>::value << std::endl;
  std::cout << "C: " << std::is_trivial<C>::value << std::endl;
  std::cout << "D: " << std::is_trivial<D>::value << std::endl;
  return 0;
}

Output:
is_trivial:
int: true
A: true
B: false
C: false
D: false


See also

is_trivially_copyable
Is trivially copyable (class template)
is_signed
Is signed type (class template)
is_unsigned
Is unsigned type (class template)