为什么信号量对象未初始化？

我正在学习使用信号量对象。但我无法初始化它。 sem_init函数总是返回值-1雨或闪耀。为什么信号量对象未初始化？

返回值-1表示第一个参数是无效的指针，说我的参考。但我找不到在我的代码打印错过。我编译在OS X

#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); 
    } 
}

来源

2012-12-12 inherithandle

在Mac OS X（10.6.8）没有sem_init()和sem_destroy()我在Xcode代码。

使用sem_open()和sem_unlink()代替。

/* 

cat semaphore_test.c 

source: 
"Why semaphore object is not initialized?", 
https://stackoverflow.com/questions/13834367/why-semaphore-object-is-not-initialized 

compiled on Mac OS X 10.6.8 with: 
gcc -ansi -pedantic -std=gnu99 -Os -Wall -Wextra -Wshadow -Wpointer-arith -Wcast-qual -Wstrict-prototypes \ 
    -Wmissing-prototypes -Wformat=2 -Wreturn-type -Wunreachable-code -finline -l pthread -o semaphore_test semaphore_test.c 

./semaphore_test 

*/ 

#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; 
static sem_t *bin_sem; 
static const char *semname = "Semaphore"; 
static int number = 0; 

char thread1[] = "A thread"; 
char thread2[] = "B thread"; 
char thread3[] = "C thread"; 

int main(void) 
{ 
    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); 
    } 
*/ 

    bin_sem = sem_open(semname, O_CREAT, 0777, 0); 
    if (bin_sem == SEM_FAILED) 
    { 
     fprintf(stderr, "%s\n", "ERROR creating semaphore semname"); 
     exit(EXIT_FAILURE); 
    } 

    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); 
    sem_unlink(semname); 
    return 0; 
} 

void * thread_snd(void * arg) 
{ 
    int i; 
    for(i = 0 ; i < 4; i++) 
    { 
     while(number != 0) 
      sleep(1); 
     number++; 
     printf("snd execution : %s, number : %d \n", (char*) arg, number); 
     //sem_post(&bin_sem); 
     sem_post(bin_sem); 
    } 
} 

void * thread_rcv(void* arg) 
{ 
    int i; 
    for(i = 0 ; i < 2; i++) 
    { 
     //sem_wait(&bin_sem); 
     sem_wait(bin_sem); 
     number--; 
     printf("rcv execution : %s number : %d \n", (char*)arg, number); 
    } 
}

参见：

来源

2013-02-28 18:43:59 chad

为什么信号量对象未初始化？

回答

相关问题