问如果持续时间太长，为什么std::condition_variable::wait_for()返回超时？

EN

//  This is 'cv_wait.cc' compile with:
//  
//    g++ -o cv_wait -std=c++2a cv_wait.cc
//
// An example showing that wait_for() returns immediately with a timeout
// return value if the duration variable is "too large".
//

#include <iostream>
#include <condition_variable>
#include <chrono>

int main(int argc, char **argv)
{
  std::condition_variable cv;
  std::mutex cv_m;

  // If num_years is "too large", e.g. 1000, then cv.wait_for()
  // returns immediately with a timeout condition!
  int num_years = 1;  // If 1000 then cv.wait_for() returns immediately!
  std::chrono::seconds timeout((uint64_t)3600 * 24 * 365 * num_years);
  std::unique_lock<std::mutex> lock(cv_m);
  if (cv.wait_for(lock, timeout, [] { return false; }))
      std::cerr << "No timeout!\n";
  else
      std::cerr << "Timeout!\n";
}