arrays - Accessing unallocated memory C++

Question

I am having this piece of code:

try
{
    int* myTestArray = new int[2];

    myTestArray[4] = 54;

    cout << "Should throw ex "  << myTestArray[4] + 1 << endl;
}
catch (exception& exception)
{ 
    cout << "Exception content: " << exception.what() << endl;
}

What is really curios for me, is that why the exception is not thrown here, since it was accessed an index which was not allocated... and why 55 is print ? Is that C++ automatically increased the size of the array ?

Answer 1

Accessing unallocated memory is not guaranteed to throw exceptions.

It's actually not guaranteed to do anything, since that's undefined behavior. Anything could happen. Beware of nasal demons.

It prints 55 because you just stored 54, fetched it back and then printed 54+1. It's not at all guaranteed to print 55, although that's often what will happen in practice. This time it worked.