pthread unusual behavoiur

Question

Is output

2 2
1 1
0 0
3 3
1610766130 4

normal behavour or bug in my code?

Code:

#ifdef __cplusplus
extern "C" {
#endif

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


#define N_TREADS 5


void *p( void* in )
{
    int w;
    void * word;
    word = in;
    w = *((int*)word);
    usleep((rand() %  1000) + 1000);
    printf( "%i %i\n", *((int*)word),w );
    pthread_exit(NULL);
    return NULL;
}

int main( int argc, char *argv[] )
{
    pthread_t threads[N_TREADS];
    int numberz[N_TREADS];
    int rc,i;
    for(i =0;i< N_TREADS; i++)
    {
        numberz[i]=i;
        rc = pthread_create( &threads[i], NULL, p, (void*)&numberz[i] );
        if( rc )
        {
            printf("error");
            exit( -1 );
        }
    }
    pthread_exit(NULL);
}


#ifdef __cplusplus
}
#endif

Douglas Leeder · Accepted Answer · 2011-05-19 11:06:58Z

3

I guess thread 4 returns after the main() stack space has been reused?

You should pthread_join your threads before numberz goes out of scipe.

answered May 19, 2011 at 11:06

Douglas Leeder

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1 Comment

Luka Rahne Over a year ago

That is great. Looks like that most examples on net have save bug.

ColWhi · Accepted Answer · 2011-05-19 11:09:00Z

1

I don't think you want the pthread_exit in main (or in p). But you should probably be using pthread_join to wait for the threads in main then exit.

answered May 19, 2011 at 11:09

ColWhi

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