Variable Size Array through Keyboard Input Verification [duplicate]

I know this question has been asked many times before. But everything I went through indicated it is not possible to declare a variable size array at run time unless we use pointers or vectors. But I am always able to take the array size input in a variable(say n) from user and then declare a array of size n. It never gives any warning or error in codeblocks ,vs code or for that matter any coding website.

   int n;
   cin>>n;

   int arr[n];
    for(int i=0;i<n;i++){
        cin>>arr[i];

    }  

My this code always works, but i don't understand How!!!!

Thanks in Advance