How to pass more than one value as an argument to a thread in C?

Question

In C, how can i pass more than one argument to a thread?

Normally, I do it in a way like,

 pthread_create(&th,NULL,dosomething,(void*)connfd);


void         


        

Answer 1

Pack the several values inside a struct on the heap (so malloc it and fill it before), then call pthread_create with a pointer to that struct.

Answer 2

About passing an array as an argument, of course you can do that. If you declare an array as,

int a[3] = {1,2,2};

a is like a label to the starting address of the array. Thus a represents a pointer. *a is equal to a[0] and *(a+1) is equal to a[1]. So you can pass the array to the thread as below:

pthread_create(&th,NULL,dosomething,(void *)a);

Inside the thread you can cast a back to an int * and use as an array.

Answer 3

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

void *genSimpleCurList(void *pnum) {
   void  *retval;

   int i,j;

   j = 0;

    // when ptread_create , how to pass a parameters such as integer arrary to pthread

   while(j<10) {
     i =*((int *)pnum)+j;
     fprintf(stderr,"pthread creat with parameter is %d\n",i);
     j++;
    } 

  return(retval);

 }

 int  main() {

 int i, *j;
 pthread_t idxtid;
 pthread_attr_t attr;
 pthread_attr_init (&attr);
 pthread_attr_setdetachstate (&attr, PTHREAD_CREATE_DETACHED);

 j = (int *) calloc (1024, sizeof (int));
  for (i = 0; i < 1024; i++) j[i] = i;

  rcode = pthread_create (&idxtid, &attr, genSimpleCurList, (void *)j);

  exit(0);
 }