example/posix/pthreads-simple_usage.c

Shows basic usage of the pthread library

//LDFLAGS = -lpthread

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>


// Structure storing input data and place for the resultof the computation
struct computation
{
    int argument;
    unsigned long result;
};

// naive implementation of the fibonacci function
unsigned long fib(int n)
{
    if(n < 2) return 1;
    else return fib(n-2) + fib(n-1);
}

// the thread's main function
void* calc_fib(void* raw_ptr)
{
    // cast the raw pointer to the proper type
    computation* c = (computation*)raw_ptr;
    // calculate the value of the fibonacci function
    // for the specified argument and store it into result
    c->result = fib(c->argument);

    return (void*)0;
}

int main(int argc, const char* argv[])
{
    // get the argument
    int arg = (argc>1)?atoi(argv[1]):42;
    if(arg <= 0) arg = 42;
    // initialize the data for the computation
    // NOTE that the object must exist during the whole
    // lifetime of the thread
    computation comp = {arg, 0};
    // start the worker thread
    pthread_t worker;
    pthread_create(&worker, (pthread_attr_t*)0, calc_fib, (void*)&comp);
    // wait for the thread to finish
    pthread_join(worker, (void**)0);
    // print the result
    fprintf(stdout, "fib(%i) = %lu\n", comp.argument, comp.result);

    return 0;
}