Is there any difference between enum : int and enum : const int

I just discovered that gcc and clang++, would let me use a const int for the underlying type of an enum. I wonder if that has any utility of if for all purposes it is the same as having an enum based on int.

I thought that may be it would make the enum instance not assignable, but it was not the case. (And to be honest, I thought it would not compile in the same way that you can't make a class derived from a const base type class C2 : const C1{})

**Is there any use or subtle difference between enum : int and enum : const int? ** If no, why would the compiler allow it?

Example:

#include<iostream>
enum A : const int{ // is this the same as enum A : int ?
   no = 0,
   si
};

int main(){ 
   A a; 
   a = si; // is asignable
   a = no; // twice
   std::cout << (int)a << std::endl; // prints '0'
   return 0;
}

---

Funny that I can do this enum A : volatile int as well. (Fortunately, I can't do this enum A : int& or enum A : int*.)