std::num_put<CharT,OutputIt>:: ~num_put

From cppreference.com
Defined in header <locale>
protected : ~num_put ( ) ;

Destructs a std:: num_put facet. This destructor is protected and virtual (due to base class destructor being virtual). An object of type std:: num_put , like most facets, can only be destroyed when the last std::locale object that implements this facet goes out of scope or if a user-defined class is derived from std:: num_put and implements a public destructor.

Example

#include <iostream>
#include <locale>
 
struct Destructible_num_put : public std::num_put<wchar_t>
{
    Destructible_num_put(std::size_t refs = 0) : num_put(refs) {}
    // note: the implicit destructor is public
};
 
int main()
{
    Destructible_num_put dc;
    // std::num_put<wchar_t> c; // compile error: protected destructor
}