Deep thoughts about order

The adventures of our friend Joe do not end here, because shortly after learning that the proper order of class members is not necessarily an alphabetical one, he was given a task that involved executing some code in a parallel manner. Since he learned everything about threads and associated features by watching a quick introductory tutorial to the subject by some guy on TikTok, he felt he was up to the task, and shortly, the following code was committed to the repository (please bear with the authors in this case; due to some pathological manifestations of copyright and intellectual property litigations, we cannot show the original code that took the entire development team two weeks to debug and fix. The example code is actually just trying to recreate the scenario that Joe so successfully implemented):

#include <cstdio>
#include <thread>
#include <chrono>
using namespace std::chrono_literals;
struct bar {
  bar() : i(new long...