pthreads - About the parameter of function pthread_create? -

we know call pthread this:

int pthread_create(pthread_t *thread, const pthread_attr_t *attr,                      void *(*start_routine) (void *), void* arg); 

hi guys, want know why return type of third parameter void*? why not void?

because there no way start function know kind of data developer wants return function use void* can point type. developer of start function cast void* appropriate type returned before using whatever void* points to. start function can return pointer may in point anything. if start function declared return void, means function returns nothing, if developer wants start function return int, struct? example:

#include  <stdio.h> #include  <string.h> #include  <stdlib.h> #include  <pthread.h>  struct test {     char str[32];     int x; };  void *func(void*) {     struct test *eg = (struct test *)malloc(sizeof(struct test));     strcpy(eg->str,"hello world");     eg->x = 42;     pthread_exit(eg); }   int main (void) {     pthread_t id;     struct test *resp;      pthread_create(&id, null, func, null);     pthread_join(id,(void**)&resp);      printf("%s %d\n",resp->str,resp->x);      free(resp);      return 0; } 

more details on post: what void* mean , how use it?