Mobile IDEs?

Question

Why do mobile IDEs seem to not work properly? I've tried CPP N-IDE and C Mobile and both seem to handle this code incorrectly:

#include <iostream>
using namespace std;

int main() {
unsigned long long int n,x = 0;
for(x=2;x<40;x=x+2){
n=2<<x;
cout << x << " : " << n << endl ;
}
}

Seems to just output 0 for all numbers past 31
Why does this happen? Is there an offline mobile IDE that works properly?

Answer 1

I use Termux with clang package installed. The output for your code appears to be similar to Code Playground's.

https://play.google.com/store/apps/details?id=com.termux

Anyway, it looks like n would overflow for 2 << x where x > 31. This should be causing the 0 values on the IDEs you mentioned. The mobile compilers are actually working fine: Overflow is, after all, undefined behaviour and the results are dependent on compiler implementation.

https://stackoverflow.com/questions/16188263/is-signed-integer-overflow-still-undefined-behavior-in-c

Answer 2

It works on DCoder
https://play.google.com/store/apps/details?id=com.paprbit.dcoder