LinuxQuestions.org - send parameter from thread to thread

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send parameter from thread to thread

As is written in this title, i would like to send data from one thread to second by the parameter of first thread. So it should looks like this:

void * my_thread1(void *my_parameter)
{
int statement = 1;
return (void *)statement
}

main (..)
{
int local_value;
pthread_create(thread_ID,..., my_thread1,....);
//I wait as thread my_thread1 will be finished
pthread_join(&thread_ID, (void *)&local_value);
printf("That's data received from my_thread1 = %d, local_value)
}

This is a part of my program which i am interested a lot, could you help me?? (where is the error and what about sending data like float char and double????)

The problem is how you are returning your value. pthread_join really wants the address of a pointer. Allocate the memory in your thread function, then return the address of that memory. Here's a similar example that works:

Code:

#include <stdio.h>

#include <stdlib.h>    /* for abort    */

#include <string.h>    /* for strerror */

#include <pthread.h>



void* threadFunction(void* arg)

{

  int* statement;

  statement = calloc(1, sizeof(int));

  *statement = 1;

  return(statement);

}



int main( int argc, char* argv[] )

{

  pthread_t threadId;

  int*      threadResult;

  int      threadStatus;



  threadStatus = pthread_create(&threadId,

                                NULL,

                                threadFunction,

                                NULL);



  if(threadStatus != 0) {

      fprintf(stderr,

              "pthread_create failed: %s\n", 

              strerror(threadStatus));

      abort();

  }



  threadStatus = pthread_join(threadId,

                              (void**)&threadResult);



  if(threadStatus != 0) {

      fprintf(stderr,

              "pthread_join failed: %s\n", 

              strerror(threadStatus));

      abort();

  }



  printf("Data received from threadFunction: %d\n", *threadResult);



  free(threadResult);



  return(0);

}

To compile it, use:

Code:

gcc -Wall -o testthread testthread.c -lpthread

So your program works perfectly (but i used little different statement in thread fuction ThreadFunction ->
return *statement instead return(statement)

What about my program it also work great but i forgot to delete one line pthread_exit which i had in my thread function :D (God punish us for stupidity), without this line it works like it should, sending data from one thread to second

Thanks eric for help