main.cpp

#include <iostream>
#include <dirent.h>
#include <thread>

// Prepare: mkdir d; cd d; touch {0001.1000}
// Build with: g++ --std=c++11 -pthread -o main main.cpp

using namespace std;

int num_files(DIR* dir_stream) {
    int n = 0;
    struct dirent *entry;
    while ((entry = readdir(dir_stream)) != nullptr) ++n;
    return n;
}

void t_body(int iters, int expected) {
    // This won't work, directory streams cannot be reused.
    //DIR* dir_stream = opendir("d");
    for (int i = 0; i < iters; ++i) {
        DIR* dir_stream = opendir("d");
        int actual = num_files(dir_stream);
        closedir(dir_stream);
        if (actual != expected) {
            cout << "Got " << actual << " instead of " << expected << "." << endl;
            return;
        }
    }
}

int main() {
    DIR* d1 = opendir("d");
    int expected = num_files(d1);
    closedir(d1);

    int num_iterations = 10000;

    constexpr int num_threads = 10;
    thread threads[num_threads];

    for (int i = 0; i < num_threads; ++i) {
        threads[i] = thread(t_body, num_iterations, expected);
    }

    cout << "Waiting for threads" << endl;
    for (int i = 0; i < num_threads; ++i) {
        threads[i].join();
    }
}