I am playing around with using Semaphores, but I keep encountering Undefined Reference warnings, thus causing my code not to work. I pulled example code from a text, but was having issues with some of their syntax, so I went to POSIX’s semaphore tutorial and changed things around to their syntax and as a result am now getting these reference errors.
I may simply be overlooking something, but I cannot find it.
Errors:
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
What I have (It may look a bit ugly due to the way I commented things out from my old method) I also know my adding method won’t work, but I’ll get to that when I fix my syntax issues:
#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); } }