Creating new list of nested structures - c

Question

I'm having a bit of trouble trying to create a new linked list of structures from an old one. The basis of the new linked list is that the dogs that belong to specific breed specified by the user will be added to the new list and all the ones from the old list will not be carried over. I don't have a problem getting one dog into the list but I think something is wrong with my code when I try to add multiple dogs. I assumed that when I created the second temp list that points to the list results that when I added to it it would modify results but that does not seem to be the case. Any direction would be appreciated.
The last function in the code struct container* list_of_breed(char* breed) is the one I seem to be having issues with. Everything else has been working as expected. I believe the else statement is where I seem to be going wrong since when there is only one dog that matches that breed it seems to be able to make the list from them.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#define CRTDBG_MAP_ALLOC
#include <crtdbg.h>
#pragma warning(disable: 4996)
// used to create a linked list of containers, each contaning a "dog"
struct container {
struct dog *dog;
struct container *next;
} *list = NULL;
// used to hold dog information and linked list of "checkups"
struct dog {
char name[30];
char breed[30];
struct checkup *checkups;
};
// used to create a linked list of checkups containing "dates"
struct checkup {
char date[30];
struct checkup *next;
};
void flush();
void branching(char);
void helper(char);
void remove_all(struct container*);
void display(struct container*);
void add_dog(char*, char*);
struct dog* search_dog(char*);
void add_checkup(char*, char*);
struct container* list_of_breed(char*);
int main()
{
char ch = 'i';
printf("Dog Adoption Center\n\n");
do
{
printf("Please enter your selection:\n");
printf("\ta: add a new dog to the list\n");
printf("\ts: search for a dog on the list\n");
printf("\tc: add a checkup date for dog\n");
printf("\tb: display list of dogs of breed\n");
printf("\tq: quit\n");
ch = tolower(getchar());
flush();
branching(ch);
} while (ch != 'q');
remove_all(list);
list = NULL;
_CrtDumpMemoryLeaks();
return 0;
}
void flush()
{
int c;
do c = getchar(); while (c != '\n' && c != EOF);
}
void branching(char c)
{
switch (c)
{
case 'a':
case 's':
case 'r':
case 'c':
case 'l':
case 'b':
case 'n': helper(c); break;
case 'q': break;
default: printf("Invalid input!\n");
}
}
void helper(char c)
{
if (c == 'a')
{
char input[100];
printf("\nPlease enter the dog's info in the following format:\n");
printf("name:breed\n");
fgets(input, sizeof(input), stdin);
input[strlen(input) - 1] = '\0';
char* name = strtok(input, ":");
char* breed = strtok(NULL, ":");
struct dog* result = search_dog(name);
if (result == NULL)
{
add_dog(name, breed);
printf("\nDog added to list successfully\n\n");
}
else
printf("\nThat dog is already on the list\n\n");
}
else if (c == 's' || c == 'r' || c == 'c' || c == 'l')
{
char name[30];
printf("\nPlease enter the dog's name:\n");
fgets(name, sizeof(name), stdin);
name[strlen(name) - 1] = '\0';
struct dog* result = search_dog(name);
if (result == NULL)
printf("\nThat dog is not on the list\n\n");
else if (c == 's')
printf("\nBreed: %s\n\n", result->breed);
else if (c == 'c')
{
char date[30];
printf("\nPlease enter the date of the checkup:\n");
fgets(date, sizeof(date), stdin);
date[strlen(date) - 1] = '\0';
add_checkup(name, date);
printf("\nCheckup added\n\n");
}
}
else if (c == 'b')
{
char breed[30];
printf("\nPlease enter the breed:\n");
fgets(breed, sizeof(breed), stdin);
breed[strlen(breed) - 1] = '\0';
struct container* result = list_of_breed(breed);
printf("\nList of dogs with breed type %s:\n\n", breed);
display(result);
remove_all(result);
result = NULL;
}
}
void remove_all(struct container* dogs)
{
struct checkup* temp;
if (dogs != NULL)
{
remove_all(dogs->next);
while (dogs->dog->checkups != NULL)
{
temp = dogs->dog->checkups;
dogs->dog->checkups = dogs->dog->checkups->next;
free(temp);
}
free(dogs->dog);
free(dogs);
}
}
void display(struct container* dogs)
{
struct container* container_traverser = dogs;
if (container_traverser == NULL)
{
printf("\nThere are no dogs on this list!\n\n");
return;
}
while (container_traverser != NULL)
{
printf("Name: %s\n", container_traverser->dog->name);
printf("Breed: %s\n", container_traverser->dog->breed);
printf("Checkups on file: ");
struct checkup* ptr = container_traverser->dog->checkups;
if (ptr == NULL)
{
printf("No checkups documented.");
}
else
{
while (ptr != NULL)
{
printf("\n%s", ptr->date);
ptr = ptr->next;
}
}
printf("\n\n");
container_traverser = container_traverser->next;
}
}
void add_dog(char* name, char* breed)
{
struct dog *tempDog = (struct dog *) malloc(sizeof(struct dog));
strcpy(tempDog->name, name);
strcpy(tempDog->breed, breed);
struct container *tempCont = (struct container *) malloc(sizeof(struct container));
tempCont->dog = tempDog;
tempCont->next = list;
list = tempCont;
}
struct dog* search_dog(char* name)
{
struct container *temp = list;
while (temp != NULL) {
if (strcmp(temp->dog->name, name) == 0) {
return temp->dog;
}
temp = temp->next;
}
return NULL;
}
void add_checkup(char* name, char* date)
{
struct container *tempList = (struct container *) malloc(sizeof(struct container));
tempList = list;
struct checkup *tempCheck = (struct checkup *) malloc(sizeof(struct checkup));
while (tempList != NULL) {
if (strcmp(tempList->dog->name, name) == 0) {
strcpy(tempCheck->date, date);
tempList->dog->checkups = tempCheck;
}
tempList = tempList->next;
}
}
//THIS IS THE FUNCTION I AM HAVING ISSUES WITH SPECIFICALLY RETURNING MULTIPLE STRUCTURES TO THE LIST
struct container* list_of_breed(char* breed)
{
struct container* result = NULL;
struct container* temp = list;
while (temp != NULL) {
struct dog* tempDog = (struct dog*) malloc(sizeof(struct dog));
tempDog = temp->dog;
if (strcmp(temp->dog->breed, breed) == 0) {
struct container *cont_add = (struct container*) malloc(sizeof(struct container));
struct dog *dog_add = (struct dog*) malloc(sizeof(struct dog));
strcpy(dog_add->name, temp->dog->name);
strcpy(dog_add->breed, breed);
dog_add->checkups = temp->dog->checkups;
cont_add->dog = dog_add;
if (result == NULL) {
result = cont_add;
}
else {
struct container* temp2 = result;
while (temp2->next != NULL) {
temp2 = temp2->next;
}
temp2->next = cont_add;
}
}
temp = temp->next;
}
return result;
}

Answer 1

I noticed the following problems. You have couple of uninitialized members, and you use them. As a consequence, your program has undefined behavior.
First One
In add_doc, you are not initializing the member checkupsof the newly malloc'edstruct dog`. Add
tempDog->checkups = NULL;
after the line
strcpy(tempDog->breed, breed);
Second One
In list_of_breed, you are not setting the next member of cont_dog before using it.
Add the line
cont_add->next = NULL;
after
cont_add->dog = dog_add;
Future Problem
In list_of_breed, you have the line:
dog_add->checkups = temp->dog->checkups;
That makes a shallow copy of checkups. In order to avoid freeing checkups more than once, you will need to make deep copies of checkups.