C ++ 11 <chrono> overflow guarantees

Question

I have this piece of code:

auto time_point_a = std::chrono::high_resolution_clock::now();
while (true) {
  auto time_point_a = std::chrono::high_resolution_clock::now();
  auto counter_ms = std::chrono::duration_cast<std::chromo::milliseconds(time_point_a - time_point_b);
  // more code
std::count << counter_ms.count() << std::endl;
}

Is it mandatory for counter_ms.count () to always return a valid value? Is there any chance that count () throws away? What happens if counter_ms exceeds the size of its main integral type (I believe it is long)? My program will run for several days in a row, and I need to know what happens if / when counter_ms gets too big.

Answer 1

Is it mandatory for counter_ms.count () to always return a valid value?

counter_ms . - .count() , , .

, count() ?

- noexcept :

• noexcept std:: lib.
• , , .

counter_ms , , , .

, .

, counter_ms ( , )?

:

#include <chrono>
#include <iostream>
#include "type_name.h"

int
main()
{
    std::cout << type_name<std::chrono::milliseconds::rep>() << '\n';
}

"type_name.h" . :

long long

, 45 . +/- 557 . milliseconds :

#include <chrono>
#include <iostream>

int
main()
{
    using days = std::chrono::duration
        <int, std::ratio_multiply<std::ratio<24>, std::chrono::hours::period>>;
    using years = std::chrono::duration
        <int, std::ratio_multiply<std::ratio<146097, 400>, days::period>>;

    std::cout << std::chrono::duration_cast<years>
        (std::chrono::milliseconds::min()).count() << " years\n";
    std::cout << std::chrono::duration_cast<years>
        (std::chrono::milliseconds::max()).count() << " years\n";
}

:

-292277024 years
 292277024 years

, <chrono>, (lib++). , , , 45- , 64- .

, , ( undefined).