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POWhy semaphore object is not initialized?
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2012-12-12T06:52:24.703
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2013-03-01T15:39:24.210
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<p>I'm learning to use semaphore object. But I can't initialize it. A sem_init function always return value -1 rain or shine.</p> <p>return value -1 indicates first argument is not valid pointer, say my reference. But I can't find miss print in my code. I compiled my code in Xcode on OS X.</p> <pre><code>#include <stdio.h> #include <unistd.h> #include <stdlib.h> #include <pthread.h> #include <semaphore.h> void * thread_snd(void *arg); void * thread_rcv(void* arg); sem_t bin_sem; int number = 0; char thread1[] = "A thread"; char thread2[] = "B thread"; char thread3[] = "C thread"; int main(int argc, char** argv) { pthread_t t1, t2 ,t3; void *thread_result; int state; state = sem_init(&bin_sem, 0, 0); if(state != 0) { puts("fail to initialize semaphore"); exit(1); } pthread_create(&t1, NULL, thread_snd, &thread1); pthread_create(&t2, NULL, thread_rcv, &thread2); pthread_create(&t3, NULL, thread_rcv, &thread3); pthread_join(t1, &thread_result); pthread_join(t2, &thread_result); pthread_join(t3, &thread_result); printf("final number : %d \n", number); sem_destroy(&bin_sem); return 0; } void * thread_snd(void * arg) { int i; for(i = 0 ; i < 4; i++) { while(number != 0) sleep(1); number++; printf("execution : %s, number : %d \n", (char*) arg, number); sem_post(&bin_sem); } } void * thread_rcv(void* arg) { int i; for(i = 0 ; i < 2; i++) { sem_wait(&bin_sem); number--; printf("execution : %s number : %d \n", (char*)arg, number); } } </code></pre>
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Why semaphore object is not initialized?
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