I’m running some code for a program in python, and when I run c++ I need to handle standard input for my it, such as scanf and cin. I am running the compiled c++ program using subprocess.Popen. I expect it to time out and raise an exception when I don’t give any stdin, but my program ends straight away and prints Killed on the console.
Here’s part of my class, which I believe is sufficient

    def run(
        self, args: List[str] = [], stdin: str = "", timeout: int = 30
    ) -> Tuple[int, str, str]:

        process = subprocess.Popen(
            [os.path.join(self.temp_file_folder, "build", self.target_file_name)]
            + args,
            stdin=subprocess.PIPE,
            stdout=subprocess.PIPE,
            stderr=subprocess.PIPE,
            text=True,
        )

        try:
            stdout, stderr = process.communicate(input=stdin, timeout=timeout)
        except subprocess.TimeoutExpired as e:
            process.kill()
            raise RunTimeoutError(f"Expired in {timeout}s")

        return (process.returncode, stdout, stderr)

When I use 30s, the program exits directly after running process.communicate and prints Killed on the console without any exception. But when I use 5s, it throws an exception as I expect.
I call my function without any stdin.

when timeout == 30 output like this:

when timeout == 5 output like this:

This is the c++ code I was running at the time

#include <iostream>
#include <cmath>
#include <limits>
#include <iomanip>

int main()
{
    int N;
    double sum = 0;
    double product = 1;

    std::cout << "Please enter an integer  N between 1 and 50: ";
    std::cin >> N;

    while (std::cin.fail() || N < 1 || N > 50)
    {
        std::cin.clear();
        std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
        std::cout << "Input error, please enter an integer N between 1 and 50: ";
        std::cin >> N;
    }

    std::cout << N << ":" << std::endl;
    for (int i = N - 1; i >= 0; i--)
    {
        int value = pow(2, i);
        sum += value;
        product *= value;
        std::cout << value << (i > 0 ? ", " : "\n");
    }

    double geometric_mean = pow(product, 1.0 / N);
    std::cout << std::fixed << std::setprecision(2);
    std::cout << "sum: " << sum << std::endl;
    std::cout << "avg: " << geometric_mean << std::endl;

    return 0;
}

I’m not quite sure if it’s a problem with the c++ code, or with my own code

My environment is python 3.8.10 Ubuntu 20.04.6 LTS