#include <chrono>
#include <iomanip>
#include <iostream>

// Illustrates a bug in the clang compiler.
// When overflow occurs in std::chrono computations, the resultant values don't
// compare as they should.
//
// Failure case: optimized at O2 or O3
//   clang++ -std=c++11 -O2 duration_compare_fail.cc
//   ./a.out
//
// Success case: optimized at O0 or O1
//   clang++ -std=c++11 -O1 duration_compare_fail.cc
//   ./a.out
//
// See documentation below for expected outcome.

using std::chrono::duration;
using std::chrono::steady_clock;
using std::chrono::time_point;
using std::ostream;

// Print out a duration as number of ticks * ratio.
template <typename rep, typename per>
ostream& operator<<(ostream& out, const duration<rep, per>& duration) {
  out << duration.count() << " * " << per::num << " / " << per::den;
  return out;
}

// Prints a time period by printing its underlying duration from epoch.
template <typename c, typename d>
ostream& operator<<(ostream& out, const time_point<c, d>& time) {
  out << time.time_since_epoch();
  return out;
}

// Simply show a variable/expression and its value.
#define PRINT(v) std::cout << #v << ": " << (v) << "\n";

int main() {
  std::cout << std::setprecision(16);

  std::cout << "Math directly with longs works\n";
  steady_clock::duration::rep a = 9223372036854775807L;
  steady_clock::duration::rep b = 2098958597616352L;
  steady_clock::duration::rep c;
  PRINT(a);
  PRINT(b);
  PRINT(c = a + b);
  // This will print true; c is a result of overflow and is negative.
  PRINT(c < b);

  std::cout << "\nComparable math with durations fails\n";
  const steady_clock::duration delay = steady_clock::duration::max();
  const time_point<steady_clock> now = steady_clock::now();
  const time_point<steady_clock> wrap = now + delay;
  PRINT(delay);
  PRINT(now);
  PRINT(wrap);
  // This will only print true with low optimization. However, the count for
  // each time point's
  PRINT(wrap < now);
  PRINT(wrap.time_since_epoch() < now.time_since_epoch());
  PRINT(wrap.time_since_epoch().count() < now.time_since_epoch().count());

  return 0;
}