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Showing content from https://cplusplus.com/reference/type_traits/is_pod/ below:

class template

<type_traits>

std::is_pod

template <class T> struct is_pod;

Is POD type

Trait class that identifies whether T is a POD type.

A POD type (which stands for Plain Old Data type) is a type whose characteristics are supported by a data type in the C language, either cv-qualified or not. This includes scalar types, POD classes and arrays of any such types.

A POD class is a class that is both trivial (can only be statically initialized) and standard-layout (has a simple data structure), and thus is mostly restricted to the characteristics of a class that are compatible with those of a C data structure declared with struct or union in that language, even though the expanded C++ grammar can be used in their declaration and can have member functions.

is_pod inherits from integral_constant as being either true_type or false_type, depending on whether T is a POD 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 constants Inherited from integral_constant:
member constant definition value either true or false
Member functions Inherited from integral_constant:

operator bool: Returns value (public member function)

Example

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

struct A { int i; };            // C-struct (POD)
class B : public A {};          // still POD (no data members added)
struct C : B { void fn(){} };   // still POD (member function)
struct D : C { D(){} };         // no POD (custom default constructor)

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

Output:

is_pod:
int: true
A: true
B: true
C: true
D: false