C++ variant of Figure 4.11

onethread.cpp

#include <cstdlib>
#include <iostream>

#include <pthread.h>

using std::cout;
using std::cerr;
using std::endl;

// Don't forget to compile with -pthread

int sum = 0;
void *runner(void *param);

int main(int argc, char *argv[])
{
    if (argc != 2) {
        cerr << "Usage: " << argv[0] << " N" << endl;
        return EXIT_FAILURE;
    }

    pthread_t tid;
    errno = pthread_create(&tid, NULL, runner, argv[1]);
    if (errno != 0) {
        perror("pthread_create");
        return EXIT_FAILURE;
    }

    errno = pthread_join(tid, NULL);
    if (errno != 0) {
        perror("pthread_join");
        return EXIT_FAILURE;
    }

    cout << "sum = " << sum << endl;

    return EXIT_SUCCESS;
}

void *runner(void *param)
{
    char *s = reinterpret_cast<char *>(param);
    auto upper = atoi(s);

    for (auto i = 1; i < upper; i++) {
        sum += i;
    }

    pthread_exit(NULL);
}