Hey everyone! I've only been programming for about two weeks, and I'm feeling a bit lost. I've got this homework due tomorrow where I need to shift an element in a square array in a circular manner. Specifically, I have to shift an element clockwise and then shift it to the inner array and shift it counterclockwise.
Here's my dilemma: I started coding on my MacBook and everything seemed fine. But when I moved to my Windows PC and ran the same code, the output was completely different! It's the same IDE (CLion), and I've double-checked that the code is identical. In fact, I even copied my code from my MacBook to my Windows PC, but I'm still getting different outputs.
On the MacBook, the output was:
1 2 3 4 5
2 3 4 5 1
But on Windows, I got:
1 2 3 4 5
2 3 4 5 32758
I feel like I'm missing something fundamental here that I should have learned. I'm not asking anyone to debug my code—just trying to understand why I'm seeing different results. Thanks for your help!
2 Answers
You're spot on! Different operating systems and even different versions of C/C++ compilers can treat undefined behavior in unpredictable ways. The weird output you're experiencing is just one such example. The same code can return valid results on one machine but fail spectacularly on another. As you continue learning, you'll get better at spotting these types of issues. Just remember: always stay within the array bounds to avoid headaches!
The issue is likely in this part of your code:
for(i=0; i<n; i++){
a[i] = a[i+1];
}
What happens here is that you’re accessing an element outside of the bounds of your array in the last iteration. In C/C++, going past the boundaries of an array doesn’t throw an error, which can lead to accessing random memory data. That's why you see different outputs on different machines—you're getting undefined behavior since the memory layout can vary between your Mac and Windows system. Stick to accessing valid array indices to avoid this kind of problem!
Thanks for explaining this! I was puzzled why the code didn't crash on my Mac. I guess the undefined behavior can sometimes give you what you want (or something totally random).
Just to clarify for you—when your loop runs with `i` reaching 4, you're trying to access `a[i+1]`, which means `a[5]`. That's definitely out of bounds, and it can cause unpredictable results, hence the 32758 showing up on your Windows output.