have i written this program correctly ?

Code:

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

typedef struct node_s
{
        void *data;
        struct node_s *next;

}node;


int add_to_link_list(node **head)
{
        node *ptr;
        int temp;

        ptr = malloc(sizeof(node));

        if (ptr == NULL)
        {
                fprintf(stderr, "Memory allocation failed\n");
                return (1);
        }

        printf("Enter data\n");
        if (scanf("%d", &temp) != 1)
        {
                fprintf(stderr, "Error while entering data\n");
                return (1);
        }

        ptr->data = malloc(sizeof(int));
        if (ptr->data == NULL)
        {
                fprintf(stderr, "Memory allocation failed\n");
                return (1);
        }

        (int) ptr->data = temp;
        ptr->next = *head;
        *head = ptr;

        return (0);
}

int main(void)
{
        node *head = NULL;
        node *ptr;
        int n, i;

        printf("How many numbers\n");
        if (scanf("%d", &n) != 1)
        {
                fprintf(stderr, "Error while enterning list size\n");
                return (EXIT_FAILURE);
        }

        for (i = 0; i < n; i++)
        {
                if (add_to_link_list(&head))
                {
                        fprintf(stderr, "add_to_link_list failed\n");
                        return (EXIT_FAILURE);
                }
        }

        ptr = head;

        while (ptr != NULL)
        {
                printf("%d\n", ptr->data);
                ptr = ptr->next;
        }

        return (EXIT_SUCCESS);
}

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btw i didn't understand how the statement

printf("%d\n", ptr->data) was acceptable. The compiler did not warn me to do a typecast or anything. Can I get away witht his while using scanf as well ? scanf("%d", &ptr->data) ?

This is what your compiler should have told you:

Code:

---

temp.c: In function `add_to_link_list':
temp.c:39: warning: use of cast expressions as lvalues is deprecated
temp.c: In function `main':
temp.c:72: warning: int format, pointer arg (arg 2)

---

Quote:

---

Originally Posted by tabstop

This is what your compiler should have told you:

Code:

---

temp.c: In function `add_to_link_list':
temp.c:39: warning: use of cast expressions as lvalues is deprecated
temp.c: In function `main':
temp.c:72: warning: int format, pointer arg (arg 2)

---

---

I changed my program to the following and its working perfectly well :

Code:

---


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

typedef struct node_s
{
        void *data;
        struct node_s *next;

}node;


int add_to_link_list(node **head)
{
        node *ptr;
        int temp;

        ptr = malloc(sizeof(node));

        if (ptr == NULL)
        {
                fprintf(stderr, "Memory allocation failed\n");
                return (1);
        }

        ptr->data = malloc(sizeof(int));
        if (ptr->data == NULL)
        {
                fprintf(stderr, "Memory allocation failed\n");
                return (1);
        }

        printf("Enter data\n");
        if (scanf("%d", &ptr->data) != 1)
        {
                fprintf(stderr, "Error while entering data\n");
                return (1);
        }
       
        ptr->next = *head;
        *head = ptr;

        return (0);
}

int main(void)
{
        node *head = NULL;
        node *ptr;
        int n, i;

        printf("How many numbers\n");
        if (scanf("%d", &n) != 1)
        {
                fprintf(stderr, "Error while enterning list size\n");
                return (EXIT_FAILURE);
        }

        for (i = 0; i < n; i++)
        {
                if (add_to_link_list(&head))
                {
                        fprintf(stderr, "add_to_link_list failed\n");
                        return (EXIT_FAILURE);
                }
        }

        ptr = head;

        while (ptr != NULL)
        {
                printf("%d\n", ptr->data);
                ptr = ptr->next;
        }

        return (EXIT_SUCCESS);
}

---

Define "perfectly well". Your print statements should be printing, not garbage necessarily, but not actual values.

Quote:

---

Originally Posted by tabstop

Define "perfectly well". Your print statements should be printing, not garbage necessarily, but not actual values.

---

They print actual values correctly.

I'm using digital mars compiler and used the -a option(strict ansi c/c++) and got no warnings or errors.

Somehow, you're still suppressing warnings (i.e., you have a valid program, but it doesn't do what you think it does) -- and here you have two warnings that cancel out:

Code:

---

temp.c: In function `add_to_link_list':
temp.c:33: warning: int format, pointer arg (arg 2)
temp.c:15: warning: unused variable `temp'
temp.c: In function `main':
temp.c:71: warning: int format, pointer arg (arg 2)

---

So your pointer isn't valid, you're storing the value of the integer as the value of the pointer.

yes, i realised that error.

Code:

---

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

typedef struct node_s
{
        void *data;
        struct node_s *next;

}node;


int add_to_link_list(node **head)
{
        node *ptr;
   
        ptr = malloc(sizeof(node));
        if (ptr == NULL)
        {
                fprintf(stderr, "Memory allocation failed\n");
                return (1);
        }

        ptr->data = malloc(sizeof(int));
        if (ptr->data == NULL)
        {
                fprintf(stderr, "Memory allocation failed\n");
                return (1);
        }

        printf("Enter data\n");
        if (scanf("%d", ptr->data) != 1)
        {
                fprintf(stderr, "Error while entering data\n");
                return (1);
        }
       
        ptr->next = *head;
        *head = ptr;

        return (0);
}

int main(void)
{
        node *head = NULL;
        node *ptr;
        int n, i;
        int *temp;
       
        printf("How many numbers\n");
        if (scanf("%d", &n) != 1)
        {
                fprintf(stderr, "Error while enterning list size\n");
                return (EXIT_FAILURE);
        }

        for (i = 0; i < n; i++)
        {
                if (add_to_link_list(&head))
                {
                        fprintf(stderr, "add_to_link_list failed\n");
                        return (EXIT_FAILURE);
                }
        }

        ptr = head;
     
        while (ptr != NULL)
        {
                temp = (int *)ptr->data;
                printf("%d\n",*temp);
                ptr = ptr->next;
        }

        return (EXIT_SUCCESS);
}

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