Conditional Statement is never triggered within Chrono Program

Question

Abstract:

I wrote a short program dealing with the Chrono library in C++ for experimentation purposes. I want the CPU to count as high as it can within one second, display what it counted to, then repeat the process within an infinite loop.

Current Code:

#include <iostream>
#include <chrono>

int counter()
{
    int num = 0;
    auto startTime = std::chrono::system_clock::now();

    while (true)
    {
        num++;
        auto currentTime = std::chrono::system_clock::now();
        if (std::chrono::duration_cast<std::chrono::seconds>(currentTime - startTime).count() == 1)
            return num;
    }
}

int main()
{
    while(true)
        std::cout << "You've counted to " << counter() << "in one second!";
    return 0;
}

Problem:

The conditional statement in my program:

if (std::chrono::duration_cast<std::chrono::seconds>(currentTime - startTime).count() == 1)

isn't being triggered because the casted value of currentTime - startTime never equals nor rises above one. This can be demonstrated by replacing the operator '==' with '<', which outputs an incorrect result, as opposed to outputting nothing at all. I don't understand why the condition isn't being met; if this program is gathering time from the system clock at one point, then repeatedly comparing it to the current time, shouldn't the integer value of the difference equal one at some point?

Answer 1

You're hitting a cout issue, not a chrono issue. The problem is that you're printing with cout which doesn't flush if it doesn't feel like it.

cerr will flush on newline. Change to cerr and add a \n and you'll get what you expect.

std::cerr << "You've counted to " << counter() << "in one second!\n";