I have the following program compiling on linux w/ gcc,
my three thread functions have been defined just omitted.

when compiling i get these errors:

/tmp/ccMjhBVI.o: In function `main':
assign5.c:(.text+0x70): undefined reference to `pthread_create'
assign5.c:(.text+0xa3): undefined reference to `pthread_create'
assign5.c:(.text+0xd6): undefined reference to `pthread_create'
/tmp/ccMjhBVI.o: In function `sqrt_thread':
assign5.c:(.text+0x4e5): undefined reference to `sqrt'

as you can see I have included pthread.h for pthread_create
and math.h for sqrt

does anyone have any ideals


#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <pthread.h>

#define NUM_STAGES 4
#define EMPTY -1
#define USR_DBL 0
#define DBL_SQRT 1
#define SQRT_POW 2
#define POW_USR 3

typedef struct stage_object
{
    pthread_mutex_t mutex;
    pthread_cond_t cond;
    int buffer;
} stage;

stage stages[NUM_STAGES] = { {PTHREAD_MUTEX_INITIALIZER,PTHREAD_COND_INITIALIZE R,EMPTY},
    {PTHREAD_MUTEX_INITIALIZER,PTHREAD_COND_INITIALIZE R,EMPTY},
    {PTHREAD_MUTEX_INITIALIZER,PTHREAD_COND_INITIALIZE R,EMPTY},
    {PTHREAD_MUTEX_INITIALIZER,PTHREAD_COND_INITIALIZE R,EMPTY} };

void* dbl_thread(void*);
void* sqrt_thread(void*);
void* pow2_thread(void*);

int main( int argc, char** argv )
{

    int status;
    int userInput;
    int pipeLine_outPut = 0;
    pthread_t dbl_thread_id, sqrt_thread_id, pow2_thread_id;

    printf("This multi-threaded program calculates pow(sqrt(x*2)),2) for a given input\n");
    printf("Enter non-neg integer to calculate, = to see contents of pipeline or non-neg integer to quit\n");

    for(scanf("%d",&userInput); userInput > 0; scanf("%d",&userInput))
    {
        if(userInput == '=')
            printf("Pipe line output: %d\n",pipeLine_outPut);
        //dbl thread
        status = pthread_create(&dbl_thread_id, NULL, dbl_thread, NULL);
        if(status != 0)
            printf("status = %d, dbl_thread not created\n",status);
        //sqrt thread
        status = pthread_create(&sqrt_thread_id, NULL, sqrt_thread, NULL);
        if(status != 0)
            printf("status = %d, sqrt_thread not created\n",status);
        //pow2 thread
        status = pthread_create(&pow2_thread_id, NULL, pow2_thread, NULL);
        if(status != 0)
            printf("status = %d, pow2_thread not created\n",status);
        //main thread consumer problem
        status = pthread_mutex_lock(&stages[POW_USR].mutex);
        if(status != 0)
            printf("status = %d, main thread mutex lock failed in consumer problem\n",status);
        while(stages[POW_USR].buffer == EMPTY)
        {
            status = pthread_cond_wait(&stages[POW_USR].cond, &stages[POW_USR].mutex); // wait for POW_USR to become full
            if(status != 0)
                printf("status = %d, main thread cond wait failed in consumer problem\n",status);
        }
        //POW_USR not EMPTY and/or has been signalled operate on POW_USR crit region
        pipeLine_outPut = stages[POW_USR].buffer; //POW_USR data consumed
        stages[POW_USR].buffer = EMPTY; //empty consumed buffer
        status = pthread_mutex_unlock(&stages[POW_USR].mutex); //POW_USR data consumed unlock mutex
        if(status != 0)
            printf("status = %d, main thread mutex unlock failed in consumer problem\n",status);
        status = pthread_cond_signal(&stages[POW_USR].cond); // POW_USR data consumed signal cond
        if(status != 0)
            printf("status = %d, main thread condition siganal failed in consumer problem\n",status);

        //main thread producer problem
        status = pthread_mutex_lock(&stages[USR_DBL].mutex);
        if(status != 0)
            printf("status = %d, main thread mutex lock failed in producer problem\n",status);
        while(stages[USR_DBL].buffer != EMPTY)
        {
            status = pthread_cond_wait(&stages[USR_DBL].cond, &stages[USR_DBL].mutex); // wait for USR_DBL to become EMPTY
            if(status != 0)
                printf("status = %d, main thread cond wait failed in producer problem\n",status);
        }
        // USR_DBL EMPTY and/or has been signalled operate on USR_DBL crit region
        stages[USR_DBL].buffer = userInput; // USR_DBL data produced
        status = pthread_mutex_unlock(&stages[USR_DBL].mutex); //USR_DBL data produced unlock mutex
        if(status != 0)
            printf("status = %d, main thread mutex unlock failed in producer problem\n",status);
        status = pthread_cond_signal(&stages[USR_DBL].cond); // USR_DBL data produced signal cond
        if(status != 0)
            printf("status = %d, main thread condition siganal failed in producer problem\n",status);
    }
    return;
}

__________________
Mike