Question

这是我的代码：

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <pthread.h>
#include <unistd.h>
#include <semaphore.h>

sem_t s1, s2;
pthread_t foo_tid, bar_tid;

void *foo(void*) {
  while(1) {
    sem_wait(&s1);
    printf("HI ");
    sem_post(&s2);
  }
}

void *bar(void*) {
  while(1) {
    sem_wait(&s2);
    printf("HO ");
    sem_post(&s1);
  }
}

int main() {
  sem_init(&s1, 0, 0);
  sem_getvalue(&s1, &foo_tid);
  sem_init(&s2, 0, 0);
  sem_getvalue(&s2, &bar_tid);
  pthread_create(&foo_tid, NULL, foo, NULL);
  pthread_create(&bar_tid, NULL, bar, NULL);
  return 0;
}

我试图获取信号量s1和s2的输出。但我不断收到这些错误：

sema.c: In function 'main':
sema.c:29:3: warning: passing argument 2 of 'sem_getvalue' from incompatible pointer type [enabled by default]
In file included from sema.c:6:0:
/usr/include/semaphore.h:72:12: note: expected 'int * __restrict__' but argument is of type 'pthread_t *'
sema.c:31:3: warning: passing argument 2 of 'sem_getvalue' from incompatible pointer type [enabled by default]
In file included from sema.c:6:0:
/usr/include/semaphore.h:72:12: note: expected 'int * __restrict__' but argument is of type 'pthread_t *'`

我还没有摆脱这个错误。如果有人能帮我解决这个问题，那将非常感激！

Answer 1

从sem_getvalue开始，值应为int：

声明int s1_val, s2_val;

  sem_init(&s1, 0, 0);
  sem_getvalue(&s1, &s1_val);
  sem_init(&s2, 0, 0);
  sem_getvalue(&s2, &s2_val);

Answer 2

第二个参数应该是指向int的指针，当你传递pthread_t的地址时。 pthread_t不是您系统中的int。

输出信号量值

2 个答案: