我正在使用信号量,但我一直遇到未定义的参考警告,从而导致我的代码无法工作。我从文本中提取了示例代码,但是他们遇到了一些语法问题,所以我去了POSIX的信号量教程并改变了它们的语法,结果我现在得到了这些引用错误。
我可能只是忽略了一些东西,但我找不到它。
错误:
Producers_Consumers.c:52: warning: return type of ‘main’ is not ‘int’
/tmp/cceeOM6F.o: In function `producer':
Producers_Consumers.c:(.text+0x1e): undefined reference to `sem_init'
Producers_Consumers.c:(.text+0x3a): undefined reference to `sem_init'
Producers_Consumers.c:(.text+0x46): undefined reference to `sem_wait'
Producers_Consumers.c:(.text+0x52): undefined reference to `sem_wait'
Producers_Consumers.c:(.text+0x5e): undefined reference to `sem_post'
Producers_Consumers.c:(.text+0x6a): undefined reference to `sem_post'
/tmp/cceeOM6F.o: In function `consumer':
Producers_Consumers.c:(.text+0x7e): undefined reference to `sem_wait'
Producers_Consumers.c:(.text+0x8a): undefined reference to `sem_wait'
Producers_Consumers.c:(.text+0x96): undefined reference to `sem_post'
Producers_Consumers.c:(.text+0xa2): undefined reference to `sem_post'
collect2: ld returned 1 exit status
我有什么(由于我从旧方法中评论出来的方式,它可能看起来有点难看)我也知道我的添加方法不起作用,但是当我修复语法问题时我会做到这一点:
#include <stdio.h>
#include <semaphore.h>
#include <string.h>
#include <pthread.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <errno.h>
#define N 10 //Number of slots in buffer
typedef int semaphore; //Semaphores ae a special kind of int
sem_t mutex; //Controls access to critical region 1
sem_t empty; //Counts empty buffer slots N
sem_t full; //Counts full buffer slots 0
int count = 0; //What we're putting in
//int buffer[N];
void producer(void) {
sem_init(&mutex, 0, 1);
//sem_init(&empty, 0, N);
sem_init(&full, 0, 0);
while(1) {
sem_wait(&empty);
sem_wait(&mutex);
//printf("Empy: %d\n",empty);
//printf("Mutex: %d\n",mutex);
//printf("Both Downs Ran\n");
//buffer = buffer + 1;
sem_post(&mutex);
sem_post(&full);
//printf("Producer produced: %d\n",buffer);
}
}
void consumer(void) {
while(1) {
sem_wait(&full);
sem_wait(&mutex);
//item = buffer;
sem_post(&mutex);
sem_post(&empty);
//printf("Consumer consumed: %d/n",item);
}
}
void main() {
}
如果您使用的是Linux系统,则需要编译并链接-pthread
标志以链接pthreads库。
gcc -pthread Producers_Consumers.c
正如Paul Griffiths指出的那样,你也可以使用更便携的-lrt
,并链接POSIX Realtime Extensions库
gcc Producers_Consumers.c -lrt
int main(void)
不是void main()
typedef int semaphore
是错误的,sem_t
应该被视为一个不透明的类型,你永远不会在你的代码中使用这个typedef。consumer
代码在producer
初始化之前使用信号量。你应该在你的main
初始化它们在ubuntu qt中遇到同样的错误。添加后
LIBS + = -lpthread -lrt
到project.pro文件都编译好了。