并发BST插入功能不起作用

Question

I am trying to implement a concurrent BST, however the code isn't working exactly as its supposed to. I am writng the parts here which is causing the problem.

void* insertfunc(void* arg)
{
    int r, i;
    for(i = 0; i < size_of_tree; i++)
    {
      r = rand();
      root = insert(root,r); //insert function is correct, it was tested on a serial BST
     }
    inorder(root); //here tree is printed properly
    printf("\n");
   return;
}

int main()
{
       char c;
        srand(time(NULL)); 
        int i;
        node* root = NULL;
        pthread_t mythreads[4];

        for(i=0; i<1; i++)
       {
             pthread_create(&mythreads[i],NULL, insertfunc,NULL);
       }

       for(i=0; i<1; i++)
       {
              pthread_join(mythreads[i],NULL);
       }
        printf("%d", root -> data); //here root is NULL and hence the segfault
}
    return 0;
}

My root is a global variable. I can't figure out why, although in my thread the value of root is changing as a node is being inserted, when the thread terminates and my main thread resumes to complete execution, why is the root NULL again?

Answer 1

There is a local

node* root = NULL;

inside main() so it is always NULL. If you have root as global then remove this as we see this will be always NULL. So segmentation fault.