Having Trouble printing a doubly linked list

Question

I am currently having trouble trying to print my doubly linked list out. The problem is either in the getSongInfo function or in the printSongInfo function. I am very new to coding and all the help is greatly appreciated. I also don't know how to use the tail pointer when using a doubly linked list.

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<malloc.h>
#pragma warning(disable : 4996)
#pragma warning(disable : 6387)

#pragma once

//structs 
typedef struct {
    char* title;
    char* artist;
    int rating;
    SongNode* next;
    SongNode* prev;
}SongNode;

//Constants 
#define kInfiniteLoop 1 
#define kStringLength 30

//Prototypes
int getNum(void);
void eliminateEndOfLine(char* buffer);
void printSongInfo(SongNode* head); 
SongNode* getSongInfo(SongNode** head, SongNode** tail, char title[], char artist[], int rating); 

int main() {


    char title[kStringLength];
    char artist[kStringLength];
    int rating = 0;
    SongNode* head = NULL;
    SongNode* tail = NULL;

    printf("Enter Title, Artist and Rating\n");
    printf("Enter'.' to get out of the loop and print list\n");

    while (kInfiniteLoop) {

        printf("Title: ");
        fgets(title, kStringLength, stdin);
        eliminateEndOfLine(title);

        if (strcmp(title, ".") == 0) {
            break;
        }

        printf("Artist: ");
        fgets(artist, kStringLength, stdin);
        eliminateEndOfLine(artist);

        printf("Rating: ");
        while (rating = getNum()) { // error check the rating this will check to make sure the rating is in the range 1-5.

            if (rating < 1 || rating>5) {
                printf("The number you have entered is invaild\n");
                rating = 0;
                printf("Rating: ");
                continue;
            }
            break;

            head=getSongInfo(&head, &tail, title, artist, rating); 
            printf("\n");
        }
    }
    printSongInfo(head);
    return 0;
}

  /*===============================================================================================================*/
  /*FUNCTION   :getNum(void)                                                                                       */
  /*PARAMETERS :void                                                                                               */
  /*RETURNS    :number                                                                                             */
  /*DESCRIPTION:This function is the user input function to get a number rating                                    */
  /*===============================================================================================================*/
  int getNum(void)
  {/* the array is 121 bytes in size; we'll see in a later lecture how we can improve this code */
      char record[121] = { 0 }; /* record stores the string */
      int number = 0;
      /* NOTE to student: indent and brace this function consistent with your others */
  /* use fgets() to get a string from the keyboard */
      fgets(record, 121, stdin);
      /* extract the number from the string; sscanf() returns a number
   * corresponding with the number of items it found in the string */
      if (sscanf(record, "%d", &number) != 1)
      {
          /* if the user did not enter a number recognizable by
           * the system, set number to -1 */
          number = -1;
      }
      return number;
  }
  
  
  
  /*=======================================================================================================*/
  /*FUCNTION      :void eliminateEndOfLine                                                                 */
  /*PARAMETER     :(char* buffer)                                                                          */
  /*RETURNS       :void                                                                                    */
  /*DESCRIPTION   :This function takes a pointer to a string and looks through the string to find the      */
  /*               newline.It takes the new line out of the string.                                        */
  /*=======================================================================================================*/
  void eliminateEndOfLine(char* buffer)
  {
      char* target = strchr(buffer, '\n');
      if (target != NULL)
      {
          *target = '\0';
      }
  }

  SongNode* getSongInfo(SongNode** head, SongNode** tail, char title[], char artist[], int rating)
  {
      SongNode *newBlock = NULL; 
  
      newBlock = (SongNode*)malloc(sizeof(SongNode)); 
      if (newBlock == NULL) {
          
          printf("No memory to be Allocated\n"); 
          return (*head); 
      }
  
      newBlock->title=(char*)malloc(strlen(title) + 1);
      if (newBlock->title == NULL) {
          printf("No memory can be allocated for title\n"); 
          return (*head); 
      }
  
      newBlock->artist = (char*)malloc(strlen(artist) + 1); 
      if (newBlock->rating == NULL) {
          printf("No memory can be alocated for artist\n"); 
          return (*head); 
      }
  
      newBlock->rating = (int)malloc(sizeof(int)); 
      if (newBlock->rating == NULL) {
          printf("No memory can be alllocated for rating \n"); 
          return (*head); 
      }
  
      strcpy(newBlock->title, title); 
      strcpy(newBlock->artist, artist); 
      newBlock->rating = rating; 
  
      newBlock->next = (*head); 
      newBlock->prev = NULL; 
  
      if ((*head) != NULL) 
          (*head)->prev = newBlock; 
  
      (*head) = newBlock; 
  
      return (*head); 
  }
  
  void printSongInfo(SongNode* head) {
      SongNode* ptr;
      ptr = head;
  
      printf("\n");
      printf("%-35s %-35s %-35s\n", "Title", "Artist","Rating");
  
      while (ptr != NULL) {
          printf("%-35s %-35s %-35d\n", ptr->title, ptr->artist);
          ptr = ptr->next;
      }
  }

Answer 1

You have a break statement in the while (rating = getnum()) loop that shouldn't be there. It will cause the loop to terminate before getting any song info.

Other problems:

newBlock->rating = (int)malloc(sizeof(int)); will leak memory, because you allocate some but never free it. Because rating is an int, memory does not need to be allocated for it. (Also, see Do I cast the result of malloc?).

getSongInfo should either return the new head, or update the current one, but not both.

Updating tail is similar to updating head, but does not need to be done all the time when inserting at the head (there's a condition that you'll need to check for).

You don't need #pragma once in a C source file. That should be in a header (and is only supported on some compilers).