c - Raw Clone system call -

i trying use raw clone system, not find proper documentation. tried write small program try it, ends segmentation fault.

i cannot understand wrong.

here small application :

define stack_size 0x10000 define bufsize 200  #define _gnu_source  void hello (){     fprintf(stderr,"hello word\n");      _exit(0);  }   int main()   {  int res;  void *stack = mmap(0, stack_size, prot_read|prot_write,                        map_private|map_anonymous, -1, 0);   pid_t ptid, tid;     printf("stack %p\n", stack + stack_size);   memset(stack, 0, stack_size);     res= syscall(sys_clone,clone_sighand|clone_fs|clone_vm|clone_files,stack + stack_size, &tid,&ptid,null );    if (!res)       hello();     printf("clone result %x\n", res);    waitpid(-1, null, __wall);    return 0;  } 

i can't recommend going clone if can use pthreads. i've had bad experience functions such malloc() in relation clone.

have looked @ man page documentation?

here example runs me. didn't examine code see why might crashing.

#define _gnu_source #include <stdio.h> #include <sched.h> #include <sys/types.h> #include <sys/wait.h> #include <linux/sched.h> #include <stdlib.h> #include <unistd.h> #include <assert.h>  // allow round page size #define round_up_to_multiple(a,b) \ ( ( (a) % (b) == 0) ? (a) : ( (a) + ( (b) - ( (a) % (b) ) ) ) )  struct argsy {     int threadnum; };  int fun(void * args) {     struct argsy * arguments = (struct argsy *) args;     fprintf(stderr, "hey!, i'm thread %d\n", arguments->threadnum);     return 0; }  #define n_threads 10 #define pagesize 4096  struct argsy arguments[n_threads];  int main() {     assert(pagesize==getpagesize());      const int thread_stack_size = 256*pagesize;     void * base = malloc((((n_threads*thread_stack_size+pagesize)/pagesize)*pagesize));     assert(base);     void * stack = (void *)round_up_to_multiple((size_t)(base), pagesize);      int = 0;     (i = 0; < n_threads; i++) {          void * args = &arguments[i];         arguments[i].threadnum = i;         clone(&fun, stack+((i+1)*thread_stack_size),              clone_files | clone_vm,             args);     }      sleep(1);      // wait not implemented     return 0; }