链接列表C代码挂起而未从“释放”功能返回

Question

For a program that I am working on, I have a doubly linked list. I now have to figure out a particular node where a particular data (called id ) becomes negative, and then dereference the following nodes and also free the memory. When I call this function (pasted below), the last print statement is executed and prints on screen. However the program doesn't return to main. It simply hangs. (Right after this function call, I have another print statement which doesn't get executed and the program hangs there endlessly).

static void clear_ghosts(particles *plist)
{
  particles * temp = plist;

  while(temp!=NULL) {
      if(temp->p->id < 0)
      {
          break;
      }
  temp = temp->next;

 }

 if(temp)
 {
     particles * current = temp;
     particles * next;
     while(current !=NULL)
     {
         next = current->next;
         free(current);
         current = next;
     }
     temp = NULL;
 }

 printf("\n Finished Clearing \n");
 return;

}

Here plist is a linked list of type struct particle * . plist has data p which itself is a struct and has member data like id etc. I need to loop through the list and terminate the list when the member id that is negative is encountered. I am getting the output "Finished Clearing", but the function is not returning to main.

What could be going wrong?

Answer 1

Are you sure all elements you are trying to free() have been allocated with malloc() ? If, for example, some of those pointers point to memory on the stack, all kinds of horrible things might happen when you try to free() them.

Answer 2

Since you say its a double-linked list you should set the previous element's next pointer to NULL:

if (temp)
{
   if ( temp != plist )
   {
     temp->prev->next = NULL;
   }
...