thread2.c

#include <stdio.h>
#include <malloc.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>
void *thread_main(void *arg);
int main(int argc, char const *argv[])
{
	pthread_t t_id;
	int thread_param = 5;
	void *thr_ret;

	if (pthread_create(&t_id, NULL, thread_main, (void *)&thread_param) != 0)
	{
		puts("pthread_create error");
		return -1;
	}

	if (pthread_join(t_id, &thr_ret)!=0)
	{
		puts("pthread_join error");
		return -1;
	}
	
	printf("Thread return message: %s \n", (char*)thr_ret);
	printf("%d\n", (int)malloc_usable_size((char*)thr_ret));
	free(thr_ret);
	return 0;
}

void *thread_main(void *arg)
{
	int i;
	int cnt =*((int *)arg);
	char *msg=(char *)malloc(sizeof(char)*50);
	strcpy(msg, "hello, i'm thread~ \n");

	for(i=0;i<cnt;i++)
	{
		sleep(1);
		puts("running thread");
	}
    printf("%d\n", (int)malloc_usable_size(msg));
	return (void*)msg;
}