Global integer array with No dimension

Question

What is the concept when we define a global array with no dimension This shows output as 16.

    #include 
    #include 
    i         


        

Answer 1

GCC assumes that arr should only have one element. The fact that you can access other elements than arr[0] without segfaulting is just a coincidence. For instance, on my machine I can access arr[1], arr[10] and arr[100] just fine, but arr[1000] causes a segfault. In general, accessing locations outside array bounds causes undefined behavior.