POSIX Producer-consumer - c

Question

I have a problem connected with producers and consumers. I have 1 producer and 3 consumers. Producer produce letters which i put in my queue, and consumers take this letters. It is considered that letter has been removed from the queue, when 2 of consumers took it, but there is an option, that consumer A and consumer C can't take the same letter(it's possible that con. A will take letter first, then con. B will take it second or con. B first, then con C(or A) second, but no possibility when A and C together).
I wrote a code solving this problem, but now I can't print enything from functions.
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <semaphore.h>
#include <unistd.h>
#include "FIFO.h"
#define semaphore sem_t
#define MAX_SIZE _SIZE
#define SLEEP 1
#define true 1
FIFO buff;
semaphore full, empty, a_read, b_read, c_read, mutex;
void randSleep(int max) {
double x = rand()/(double)RAND_MAX;
usleep( (int)floor( x*max ) );
}
void* producer_func()
{
char c='A';
while(GetAmount(&buff)<MAX_SIZE)
{
sem_wait(&empty);
sem_wait(&mutex);
Push(&buff, c);
sem_post(&mutex);
sem_post(&full);
randSleep(SLEEP);
}
pthread_exit(NULL);
}
void* consumer_a_func()
{
char c;
long int first_met;
while(true)
{
sem_wait(&a_read);
sem_wait(&full);
if (sem_getvalue(&b_read,&first_met)) printf("Error with returning b_read value");
sem_wait(&mutex);
if (first_met)
{
c = First(&buff);
sem_post(&mutex);
}
else
{
c = Pop(&buff);
sem_post(&mutex);
sem_post(&a_read);
sem_post(&b_read);
sem_post(&empty);
}
//printf("c value %s\n", c);
randSleep(SLEEP);
}
pthread_exit(NULL);
}
void* consumer_b_func()
{
char c;
long int first_met_a, first_met_c ;
while(true)
{
sem_wait(&b_read);
sem_wait(&full);
if (sem_getvalue(&a_read,&first_met_a)) printf("Error with returning a_read value");
if (sem_getvalue(&c_read,&first_met_c)) printf("Error with returning c_read value");
sem_wait(&mutex);
if (first_met_a && first_met_c)
{
c = First(&buff);
sem_post(&mutex);
}
else
{
c = Pop(&buff);
sem_post(&mutex);
sem_post(&b_read);
if (first_met_a)
sem_post(&c_read);
else
sem_post(&a_read);
sem_post(&empty);
}
//printf("c value %s\n", c);
randSleep(SLEEP);
}
pthread_exit(NULL);
}
void* consumer_c_func()
{
char c;
long int first_met;
while(true)
{
sem_wait(&c_read);
sem_wait(&full);
if (sem_getvalue(&b_read,&first_met)) printf("Error with returning b_read value");
sem_wait(&mutex);
if (first_met)
{
c = First(&buff);
sem_post(&mutex);
}
else
{
c = Pop(&buff);
sem_post(&mutex);
sem_post(&c_read);
sem_post(&b_read);
sem_post(&empty);
}
printf("c value %s\n", c);
randSleep(SLEEP);
}
pthread_exit(NULL);
}
int main()
{
Init(&buff);
sem_init(&empty, 0, MAX_SIZE);
sem_init(&full, 0, 0);
sem_init(&a_read, 0, 1);
sem_init(&b_read, 0, 1);
sem_init(&c_read, 0, 1);
sem_init(&mutex, 0, 1);
pthread_t producer, consumer_a, consumer_b, consumer_c;
pthread_create(&producer, NULL, producer_func, NULL);
printf("All right\n");
pthread_create(&consumer_a, NULL, consumer_a_func, NULL);
printf("All right\n");
pthread_create(&consumer_b, NULL, consumer_b_func, NULL);
printf("All right\n");
pthread_create(&consumer_c, NULL, consumer_c_func, NULL);
printf("All right\n");
pthread_join(&producer, (void**)NULL);
pthread_join(&consumer_a, (void**)NULL);
pthread_join(&consumer_b, (void**)NULL);
pthread_join(&consumer_c, (void**)NULL);
}
files FIFO.h, FIFO.c
error looks like
In _IO_vfprintf_internal (s=0x7ffff78ac620 <_IO_2_1_stdout_>, format=, ap=ap#entry=0x7ffff6acfe58) at vfprintf.c:1632 ()
Or segmentation fault(core dumped)
But sometimes this code runs correctly, but without any printf's which i wrote in producer-consumer functions

Answer 1

//printf("c value %s\n", c);
c is a char, to print it you should use
printf("c value %c\n", c);
You can try to compile with -Wformat, so warning will happend if you use invalid format for variables in the printf calls.