with #pragma pop_macro("int")

#include <iostream>
using namespace std;
#define int double
void main()
{
    int iOne = 1;
    cout << sizeof(iOne) << endl;
#pragma push_macro("int")
#undef int
    int iTwo = 2;
    cout << sizeof(iTwo) << endl;
#pragma pop_macro("int")
}

without #pragma pop_macro("int")

#include <iostream>
using namespace std;
#define int double
void main()
{
    int iOne = 1;
    cout << sizeof(iOne) << endl;
#pragma push_macro("int")
#undef int
    int iTwo = 2;

    cout << sizeof(iTwo) << endl;
//#pragma pop_macro("int")
}

I have just tried on vs2017, nothing different.both have no warnings/errors, work fine, and have the same output:

8

4

So, my question is:

• Why vs allows this behavior?
• Is it UB?