Thread: While loop in insertNode function is an infinite loop

My program is supposed to read in each word from an input file and add it to a linked list, but it crashes after I enter the user input because the insertNode function/method is an infinite loop.

Code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>




struct node
{
  char *data;
  struct node *next;
};




void insertNode(struct node**, char *);
void printList(struct node*);




int main()
{
  struct node *head = NULL;
  FILE *fptr;
  char file_name[20];
  char str[1000];
  int numOfChar;




  printf("Enter the name of the file: ");
  scanf("%s",file_name);




  printf("Enter the number of characters per line: ");
  scanf("%d",&numOfChar);




  fptr=fopen(file_name,"r");


  while(fscanf(fptr, "%s ", str) != EOF)
  {
      insertNode(&head, str);
  }


  fclose(fptr);
  printList(head);




  return 0;
}




void insertNode(struct node** nodeHead, char *data)
{
    struct node* new_node = malloc(sizeof *new_node);
    new_node->data = strdup(data);
    new_node->next = NULL;






    while (*nodeHead)
        nodeHead = &(*nodeHead)->next;
    *nodeHead = new_node;


}


void printList(struct node* node)
{
    while(node != NULL)
    {
        printf(" %s ", node->data);
        node = node->next;
    }
}

ok thanks for your help. I tried your method but my program still crashes. I get a segmentation fault on line 14(in the code you posted) where the for loop is.

Like I said, it worked on my machine as-is.

Maybe malloc() did not succeed? Normally, calls to malloc have their return values checked.

Code:

struct node* new_node = malloc(sizeof *new_node);
if (new_node == NULL)
{
    fprintf(stderr, "insertNode() malloc failed!\n");
    return;
}
...

See if that is the problem. If not, then the problem should definitely be elsewhere.

Yea that still did not work. The debugger is still saying there is a segmentation fault at the for loop and I have no idea why.

Did you compile without warnings? What are you using to build programs?

I ask because some compiler vendors do not supply strdup(), and that is another potential problem that can cause a segfault.

I am using the Code::Blocks IDE. I did compile without warnings.

I don't know how to help you then. I did debug my function before posting it, and even in your existing code, it worked on my machine. I'm out of ideas.

ok thanks for your help. I have no idea either.