future/example20.cpp

// future_error::what example:
#include <iostream>     // std::cout
#include <future>       // std::promise, std::future_error

int main ()
{
 std::promise<int> prom;

 try {
   prom.get_future();
   prom.get_future();   // throws std::future_error
 }
 catch (std::future_error& e) {
   std::cout << "future_error caught: " << e.what() << '\n';
   //std::cout << "future_error caught: " << e.code().message() << '\n';
 }

 return 0;
}