Question

Why the array is not overflowed (e.g. error alert) when the array is declared globally, in other why I’m able to fill it with unlimited amount of elements (through for) even it’s limited by size in declaration and it does alert when I declare the array locally inside the main ?

char name[9];


int main(){


    int i;


    for( int i=0; i<18; ++i){
    cin>>name[i];


    }

    cout<<"Inside the array: ";
    for(i=0; i<20; i++)
    cout<<name[i];

    return 0;

}

Answer 1

C++ does not have array bounds checking so the language never check to see if you have exceeded the end of your array but as others have mentioned bad things can be expected to happen.

Global variables exists in the static segment which is totally separate from your stack. It also does not contain important information like return addresses. When you exceed an array’s boundaries you are effectively corrupting memory. It just so happens that corrupting the stack is more likely to cause more visible bad things than corrupting the data segment. All of this depends on the way your operating system organizes a process’s memory.