help with id

[newdomingo]

Hi,

i have the code :

#include <iostream>
#include <pthread.h>

using namespace std;

struct arg_struct {
    int arg1;
    int arg2;
	int id;
};

void *print(void *arguments)
{
    struct arg_struct *args = static_cast<struct arg_struct *>(arguments);
    cout << args -> arg1 << "\n";
    cout << args -> arg2 << "\n";
    cout << args -> id << "\n";
    pthread_exit(NULL);
    return NULL;
}

int main()
{
    pthread_t thr;
    struct arg_struct args;
    args.arg1 = 10;
    args.arg2 = 20;
	
    pthread_t thread[4];
	
    args.id = 0;
    for(int i=0;i<4;i++){
         pthread_create(&thread[i], NULL, print, (void *)&args);
         args.id++;
    }

    for(int i=0;i<4;i++)
         pthread_join(thread[i], NULL);
	
    return 0;
}

how to view the correct thread id in the function print using the struct too ?
Can this be done directly via the pthread_create function ? How ?
I mean that the answer i receive from the function print is thread id equal to 4 for all threads, which is wrong. The correct is to have the treads id 0,1,2,3 and not only 4.

Any help please ?

[jim80y]

All four threads have a pointer to the same 'args', so they're all showing the same value of 4, which is what your for loop has incremented it to.

Cheers,
Jim