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POPosix threads problem
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copied!<p>I am trying to understand pthreads by example. I have made the following code that is giving different answers everytime I run! Could anyone explain the bug please? TIA, Sviiya</p> <p>The code is here:</p> <pre><code>#include <pthread.h> #include <stdio.h> #include <stdlib.h> #define NUM_THREADS 4 struct thread_data { int thread_id; int sum; }; struct thread_data thread_data_array[NUM_THREADS]; void *PrintHello(void *threadarg) { struct thread_data *my_data; int taskid; int sum; my_data = (struct thread_data *) threadarg; taskid = my_data->thread_id; sum = my_data->sum; printf("Hello World! It's me, thread #%d\n", taskid); return my_data; } int main () { pthread_t threads[NUM_THREADS]; int rc; long t; int sum=0; for (t=0; t < NUM_THREADS; t++) { printf("Hi! %ld\n", t); threads[t] = t; thread_data_array[t].thread_id = t; thread_data_array[t].sum = sum; rc = pthread_create(&threads[t], NULL, PrintHello, (void *) &thread_data_array[t]); } return 0; } </code></pre> <p>The output is here:</p> <pre><code>[user@office tmp]$ ./a.out Hi! 0 Hi! 1 Hello World! It's me, thread #0 Hello World! It's me, thread #1 Hi! 2 Hi! 3 Hello World! It's me, thread #2 [user@office tmp]$ ./a.out Hi! 0 Hi! 1 Hello World! It's me, thread #0 Hello World! It's me, thread #1 Hi! 2 Hi! 3 Hello World! It's me, thread #2 Hello World! It's me, thread #3 [user@office tmp]$ ./a.out Hi! 0 Hello World! It's me, thread #0 Hi! 1 Hello World! It's me, thread #1 Hi! 2 Hello World! It's me, thread #2 Hi! 3 Hello World! It's me, thread #3 [user@office tmp]$ ./a.out Hi! 0 Hi! 1 Hello World! It's me, thread #0 Hi! 2 Hi! 3 Hello World! It's me, thread #3 [user@office tmp]$ </code></pre>

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