std::codecvt::~codecvt

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

Destructs a std::codecvt facet. This destructor is protected and virtual (due to base class destructor being virtual). An object of type std::codecvt, 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::codecvt and implements a public destructor.

[edit] Example

#include <iostream>
#include <locale>
struct Destructible_codecvt : public std::codecvt<wchar_t>
{
    Destructible_codecvt(std::size_t refs = 0) : codecvt(refs) {}
    ~Destructible_codecvt() {}; // public dtor
};
int main()
{
    Destructible_codecvt dc;
    // std::codecvt<wchar_t> c;  // compile error: protected destructor
}