Question

I’ve been trying to add a new node into a linked list of profiles (for ex. facebook profiles), and I’m getting a runtime error while launching. This is what I got :

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

typedef struct friend {
    char *name;
    int age;
    char gender;
    struct friend* next;
} friend;

void node_add(friend* new);

int main(int argc, char *argv[]) {
    friend amit;
    friend *new;

    amit.name = "amit";
    amit.age = 16;
    amit.gender = 'm';

    node_add(new);
    new->name = "amit";

    printf ("name: %s\n", new->name);
    system("PAUSE");    

    return 0;
}

void node_add(friend* new) {
    new = (friend* )malloc(sizeof(friend));
    friend* head = new;
    new -> next = head;
}

I’m trying now to create a delete node function. I tried to find which node does the user wants to delete, and then delete it by doing

delete -> next = delete -> next -> next

The problem is, I need to get for the first node in the list.
Here is what I wrote:

void node_delete(friend* delete) {
    friend *temp;
    char name[256];
    int i = 0, j = 0;

    printf ("Please enter the friend's name you want to delete: \n");
    fgets (name, 256, stdin);
    fgets (name, 256, stdin);

    while (0 == (strcmp(temp -> next -> name, delete -> next -> name))) {
        temp = friend -> next;
    }
    temp -> next = temp -> next -> next;
    free (delete);
}

Answer 1

Edit:

It seems my test was a mite too quick, because there is in fact a pretty serious problem with this code, but it’s subtle:

In main() you are never actually pointing new at anything. It’s just a garbled pointer out into memory space, which might sometimes work, and most of the time, is just terrible.

friend *new; // here's your problem; change this to:
friend *new = malloc(sizeof(friend));

Also, never cast the results of malloc.

Reedit:

How a very simple linked list implementation might look:

typedef struct _node node;
struct _node {
  void *payload;
  node *next;
};

node *create_node () {
  node *retval = malloc(sizeof(node));

  retval->payload = NULL;
  retval->next = NULL;

  return retval;
}

node *add_node (node *target) {
  if (target->next)
    return;

  node *next = create_node();
  node->next = next;
}

node *node_search (node *haystack, void *needle) {
  while (haystack) {
    if (!compare(needle, haystack->payload)) {
      return haystack;
    } else {
      haystack = haystack->next;
    }
  }

  return NULL;
}

Implementation of deletion and insertion are left as an exercise to the reader.