Adding more elements than allocated space [duplicate]

Answer 1

This is badly coded with very little effort or research. This is your homework, at least spend time on it doing it corretly.

Here is some little help but not all:

#include <iostream>
using namespace std;

int main(){
    int i,n;
    int arr[10];
    n=15;
    int x;

    for(i=0;i<n;i++){
    arr[i] = x
    cout << arr[i] << endl;
    }

return 0;    
}

There is a few thing you got to do to make it work. I will not do it!

Answer 2

The behavior of the code is undefined. There is very little to be gained by reasoning about what it might do. Just fix the array size. (chances are that one of the out-of-bounds writes is overwriting the value of n).

Answer 3

C++ compiler do not bound check for array size. Sometimes it will give desired output, other time it will crash. This will lead to Undefined behavior.

You should definitely avoid it.

Answer 4

The program has undefined behaviour because the memory outside the array was overwritten.

And it is the reason why in your system the program outputed only 5 elements. Variable n was overwritten with value 5 in the following loop when the array was initialized.

//...
int arr[10];
n=15;

for(i=0;i<n;i++){
    arr[i] = 5;
}
//...

Answer 5

This type of code produces undefined behavior--that is, code whose behavior is not defined by the standard, so compilers can do anything they want about it. Don't do this. Other examples of undefined behavior include

• Divide by zero
• Reading/writing a NULL pointer
• Overflowing signed integers
• Double free
• etc...