Why don't I get a segmentation fault when I write beyond the end of an array?

Question

why is this not giving error when I compile?

#include 
using namespace std;

int main()
{
    int *a = new int[2];
    // int a[2]; // even t         


        

Answer 1

Because undefined behavior == anything can happen. You're unlucky that it doesn't crash, this sort of behavior can potentially hide bugs.

As for a being define twice - that's a bug in the compiler.