Ambiguous if and else branches: Is the behaviour defined?

Question

I recently came accross some C++ code like the following:

if(test_1)
    if(test_2)
    {
         // Do stuff
    }
    else
       exit(0);

Answer 1

Is the behaviour of this code defined according to any standard (C, C++)?

Yes, it is defined. In C (and all similar languages as I know), the "dangling else" binds to the last free if, therefore this interpretation

if(test_1)
{
    if(test_2)
    {
    }
    else
    {
    }
}

is correct.