CODEWITHSUNDEEP
c++pthreadsundefined
Brian Bercea
Brian Bercea

Reputation: 21

undefined reference in pthread

I have this error that I am unable to figure out. I don't understand why the references are undefined. the pthread_attr_t is initialized earlier as a1, and according to the parameters, I thought it should be right. Here is my code and the error. Thanks for any help in solving this mess. 

#include <iostream>
#include "buffer.h"
#include <pthread.h>
#include <semaphore.h>

using namespace std; 

sem_t sem_mutex;

/* create the semaphore */
//sem_init(&sem_mutex, 0, 1);
/* acquire the semaphore */
//sem_wait(&sem_mutex);

/*** critical section ***/

/* release the semaphore */
//sem_post(&mutex);

int insert(buffer_item item);
int remove(buffer_item *item);
//void *thread_entry(void *param);
//create_mutex_lock(&mutex, NULL);
//pthread_mutex_lock(&mutex);
//release_mutex_lock(&mutex);


int insert(buffer_item item)
{
    bool added=false;
    /* insert an item into buffer */
    item=item+1;

    cout<<"The producer added "<<item<<endl;


    if (added==true)// return 0 if successful, otherwise
        return 0; //return -1 indicating an error condition */
    else
        return -1;
}

int remove(buffer_item *item) 
{
    bool removed=false;
    item=item-1;/* remove an object from buffer and placing it in item*/

    cout<<"the consumer removed "<< item<<endl;

    if(removed==true)
        return 0;// return 0 if successful
    else
        return -1;//otherwise return -1 indicating an error condition 
}
void *thread_entry(void *param) 
{   /* the entry point of a new thread */
    pthread_t new_entry;

}

/* create the mutex lock */
//create_mutex_lock(&mutex, NULL);

/* acquire the mutex lock */
//pthread_mutex_lock(&mutex);

/*** critical section ***/

/* release the mutex lock */
//release_mutex_lock(&mutex);


int main()
{
    /* 1. Answer the three command lines argument */
    pthread_t t1;
    pthread_attr_t a1;
    buffer_item buffer=0;/* 2. Initialize buffer, mutex, semaphores, and other global vars */
    buffer_item mutex=0;
    buffer_item semaphore=0;

    insert(buffer);/* 3. Create producer thread(s) */


    /* get the default attribute */
    pthread_attr_init(&a1);

    /* create a new thread */
    pthread_create(&t1, &a1, thread_entry, NULL);
//remove(*buffer);/* 4. Create consumer thread(s) */
        /* 5. Sleep */
        /* 6. Destroy mutex and semaphores */
    return 0; /* 7. Exit */
}

error

  [Linker error] undefined reference to `_imp__pthread_attr_init' 
  [Linker error] undefined reference to `_imp__pthread_create' 
  ld returned 1 exit status

Thanks for any help you could provide!

Upvotes: 2

Views: 2648

Answers (1)

aaronman
aaronman

Reputation: 18761

The error you probably made is that you didn't compile with -lpthread or -pthread.

But it doesn't matter because C++11 has native threads

C++11 has a whole bunch of concurrency features here which are actually much nicer to use than pthreads

keep in mind that you still have to link with pthread

Upvotes: 1

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