std::add_volatile in C++ with Examples

Last Updated : 12 Jun, 2020

The std::add_volatile template of C++ STL is present in the <type_traits> header file. The std::add_volatile template of C++ STL is used to get the type T with volatile qualification. The function std::is_volatile is used to check if type T is volatile qualified or not.

Header File:

#include<type_traits>

Template Class:

template < class T >
struct add_volatile;

Syntax:

std::add_volatile<T>::value

Parameter: The template std::add_volatile accepts a single parameter T(Trait class) which is used to get the type T with volatile qualification.

Below is the program to demonstrate std::add_volatile: in C++:

Program:

// C++ program to illustrate
// std::add_volatile
#include <bits/stdc++.h>
#include <type_traits>
using namespace std;
  
// Driver Code
int main()
{
  
    // Declare variable of type
    // volatile (int, const int, const int*,
    // int * const and const int&)
    typedef add_volatile<int>::type A;
    typedef add_volatile<volatile int>::type B;
    typedef add_volatile<int* volatile>::type C;
    typedef add_volatile<volatile int*>::type D;
    typedef add_volatile<volatile int&>::type E;
  
    cout << boolalpha;
  
    // Checking the volatileness of
    // the above declared variable
    cout << "checking volatileness:"
         << endl;
  
    cout << "A: "
         << is_volatile<A>::value
         << endl;
  
    cout << "B: "
         << is_volatile<B>::value
         << endl;
  
    cout << "C: "
         << is_volatile<C>::value
         << endl;
  
    cout << "D: "
         << is_volatile<D>::value
         << endl;
  
    cout << "E: "
         << is_volatile<E>::value
         << endl;
  
    return 0;
}

Output:

checking volatileness:
A: true
B: true
C: true
D: true
E: false

Reference: http://www.cplusplus.com/reference/type_traits/add_volatile/

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