Coderpad.io is a great tool for doing technical phone screens. However, the lack of a debugger does mean that when a interviewee’s code isn’t working as expected, you must resort to “output-based debugging”. (On the plus side, it does print stack traces for seg faults.) One caveat with this is that Coderpad captures cerr and cout separately, then outputs cout messages before cerr. This causes the order of the output to not match the order of the execution of the statements. For example:

#include <iostream>
using namespace std;

int main()
{
    cout << "One" << endl;
    cerr << "Two" << endl;
    cout << "Three" << endl;
    cerr << "Four" << endl;
}

will print:

One
Three
Two
Four

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