void pointers and scanf/printf

[pereges]

have i written this program correctly ?

i'm a bit suspicious about the statement :scanf("%d", ptr->data)



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

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

}node;


int add_to_link_lis t(node **head)
{
node *ptr;

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

ptr->data = malloc(sizeof(i nt));
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_li st(&head))
{
fprintf(stderr, "add_to_link_li st failed\n");
return (EXIT_FAILURE);
}
}

ptr = head;

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

return (EXIT_SUCCESS);
}

[rahul]

Re: void pointers and scanf/printf

On Mon, 21 Jul 2008 02:52:31 +0530, pereges <Broli00@gmail. comwrote:

typedef struct node_s
{
void *data;
struct node_s *next;
>
}node;

If you want int then you should have:

typedef struct node_ {
int data;
struct node_ *next;
} node;

If you want your list to be hetrogenous, you can have a union:

typedef struct node_ {
union {
char cData;
int iData;
float fData;
};
struct node_ *next;
} node;

There was a discussion about anonymous unions invoking undefined
behaviour. So, to avoid that:

typedef struct node_ {
union {
char c;
int i;
float f;
}data;
struct node_ *next;
} node;

--
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