C compiling "undefined reference to"?

Question

I have a C code like this:

#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
int sumofinpoint=0;
int numofpoint=0;
void *montecarlo(int number)
{
    srand((unsigned int)time(NULL));
    float a = 2.0;
    int i=0;
    for (i=0;i<(int)number;i++){
        float x,y;
        x=((float)rand()/(float)(RAND_MAX)) * a -1;
        y=((float)rand()/(float)(RAND_MAX)) * a -1;
        numofpoint++;
        if((x*x + y*y) <= 1){
            sumofinpoint=sumofinpoint+1;
        }
    }
}
int main(){
    pthread_t tid[15];
    float pi;
    int number = 100000000;
    int i=0;
    for(i = 0; i<15;i++){
        pthread_create(&tid[i], NULL, montecarlo, (int)(number/15));
        pthread_join(tid[i],NULL);
    }
    pi = 4*(float)sumofinpoint/(float)number;
    printf("So pi la: %f",pi);
    return 0;
}

I compiled it in Linux, but it said that I have "Undefined reference to pthread_create" and "Undefined reference to pthread_join". But when I compile on DevC++ in Window it runs perfectly fine. Where am I wrong?

score 2 · Answer 1 · answered Mar 26 '17 at 11:06

2

Pass a -lpthread switch to gcc (assuming you're using gcc).

answered Mar 26 '17 at 11:06

letmutx

1,386
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Tks you very much. It works – A.H.John Mar 26 '17 at 11:09
Happy to help :) Accept the answer if it worked for you. – letmutx Mar 26 '17 at 11:10

C compiling "undefined reference to"?

1 Answers1