C++

Reference

<type_traits>

class template
<type_traits>

std::is_trivially_copyable

template <class T> struct is_trivially_copyable;
Is trivially copyable

Trait class that identifies whether T is a trivially copyable type.

A trivially copyable type is a type whose storage is contiguous (and thus its copy implies a trivial memory block copy, as if performed with memcpy), either cv-qualified or not. This is true for scalar types, trivially copyable classes and arrays of any such types.

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

This class inherits from integral_constant as being either true_type or false_type, depending on whether T is a trivially copyable 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_trivially_copiable example
#include <iostream>
#include <type_traits>

struct A { int i; };

struct B {
  int i,j;
  B (const B& x) : i(x.i), j(1) {};  // copy ctor
};

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

Output:
is_trivially_copyable:
int: true
A: true
B: false


See also

is_trivial
Is trivial type (class template)
is_trivially_constructible
Is trivially constructible (class template)
is_trivially_copy_constructible
Is trivially copy constructible (class template)
is_trivially_copy_assignable
Is trivially copy assignable (class template)