storing value to doubly linked list in C - c

Question

I have a doubly linked list data structure which is well formulated, as I have tested it on different inputs.
But, here is a piece of code where I have problem. I am trying to read in a line of string from a file, and store the values by converting them into integers in an array of integer called num. The code is fine unto here as I have printed the entries out and checked them. But when I try storing them into my doubly linked list, I get all the values correct except the second value which is an arbitrary long integer. I have my code and output below:
num_read is a function which reads all the values in a doubly linked list, and takes the array num and its length as arguments.
#include "DlistInterface.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
Dnode *num_read(int *,int *);
int main(){
Dnode *number;
int num[100];
char a[10];
char *lineptr = NULL;
int j = 0;
int i = 0;
int index = 0;
size_t len;
ssize_t read;
FILE *fp;
fp = fopen("Dlist_v_array.txt","r");
while ((read = getdelim(&lineptr,&len,32,fp)) != -1){
i = 0;
index = 0;
while (1){
if ((lineptr[i] == ' ') || (lineptr[i] == '\n')) break;
else a[index++] = lineptr[i++];
}
a[index] = '\0';
num[j] = atoi(a);
printf("%d ",num[j]);
j++;
}
//printf("\n %d",j);
printf("\n");
fclose(fp);
free(lineptr);
number = num_read(num, &j);
while (number != NULL){
printf("%d ",number->data);
number = number->next;
}
printf("\n");
return 0;
}
Dnode *num_read(int *n, int *len){
int k;
for (k=1; k< *len;k++){
//printf("%d ",n[k]);
}
printf("\n");
Dnode *number = (Dnode *)malloc(sizeof(Dnode *));
number->data = n[0];
number->next = NULL;
number->prev = NULL;
Dnode *another_node;
Dnode *temp;
another_node = number;
k = 1;
while(k < *len){
temp = (Dnode *)malloc(sizeof(Dnode));
temp->data = n[k++];
temp->next = NULL;
another_node->next = temp;
temp->prev = another_node;
another_node = temp;
}
return number;
}
I get this as the output:
12 21 33 4 5 6 7 8 9
12 -2109715456 33 4 5 6 7 8 9
The first line of output is because the verification of values read in the number array, which is correct according to the values in the .txt file.
But the same values on the next line have their corresponding second entries to be a weird number, which happens to be their always, no matter what I do.
I desperately need help on this one. I will be very thankful to you all for the help. Please help!!!

Answer 1

Incorrect amount of memory assigned #BLUEPIXY.
// Dnode *number = (Dnode *)malloc(sizeof(Dnode *));
Dnode *number = (Dnode *)malloc(sizeof(Dnode));
To avoid this mistake in the future, and to create simpler original and maintainable code, use;
// pointer = malloc(sizeof *pointer * number_elements)
Dnode *number = malloc(sizeof *number); // number_elements == 1 in OP's case
// check pointer
if (number == NULL) return NULL; // detect and handle out-of-memory somehow
This has advantages
In C, the cast on malloc() is not needed.
by using the sizeof *pointer rather than sizeof(element_type), less chance to get the wrong type, as OP did in this post, and less to update should the type change.
By using the sizeof() first, the memory needs are calculated in at least size_t math. This becomes important with large programs: Consider int h,w; malloc(sizeof *pointer*h*w) vs. malloc(h*w*sizeof *pointer) where h*w overflowed int math, but not size_t math.
Always check for out-of-memory. At a minimum, it saves time in debugging as at least you know, proper memory allocated. Note: on some systems, if number_elements is 0 (and so is sizeof *pointer * number_elements) allocating 0 bytes may return NULL and that is not an out of memory condition.
pointer = malloc(sizeof *pointer * number_elements)
if (pointer == NULL && number_elements > 0) Handle_OOM();