disturbing issue I'm having with LinkedList in C language, when I count how many nodes should be

Hello world!! @Middleware & OS
There is this disturbing issue I'm having with

LinkedList

LinkedList

LinkedList

LinkedList in

language, when I count how many nodes should be in the list, I always get 1

LL count: 1

LL count: 1

LL count: 1

LL count: 1

Here is the relevant code to get the last element , to add, and to count

void addLL(LL * head)
{
LL *newNode;
LL *tail = getLastNode(head);

newNode = malloc(sizeof(LL));
if(newNode != DEF_NULL)
{
    newNode->ID=-1;
    newNode->TCB=-1;
    newNode->next = DEF_NULL;

    if(!head) head = newNode;
    else tail->next = newNode;      
}   
}

LL * getLastNode(LL * head)
{
    LL *temp = head;
    while(temp->next != DEF_NULL)
    {
        temp = temp->next;
    }
    return temp;
}

CPU_INT32U countLL(LL * head)
CPU_INT32U countLL(LL * head)
{
    CPU_INT32U elements = 0;
    LL * temp = head;
    while(temp->next != DEF_NULL)
    {
        temp = temp->next;
        elements++;
    }
    return elements;
}

void addLL(LL * head)
{
LL *newNode;
LL *tail = getLastNode(head);

newNode = malloc(sizeof(LL));
if(newNode != DEF_NULL)
{
    newNode->ID=-1;
    newNode->TCB=-1;
    newNode->next = DEF_NULL;

    if(!head) head = newNode;
    else tail->next = newNode;      
}   
}

LL * getLastNode(LL * head)
{
    LL *temp = head;
    while(temp->next != DEF_NULL)
    {
        temp = temp->next;
    }
    return temp;
}

CPU_INT32U countLL(LL * head)
CPU_INT32U countLL(LL * head)
{
    CPU_INT32U elements = 0;
    LL * temp = head;
    while(temp->next != DEF_NULL)
    {
        temp = temp->next;
        elements++;
    }
    return elements;
}

void addLL(LL * head)
{
LL *newNode;
LL *tail = getLastNode(head);

newNode = malloc(sizeof(LL));
if(newNode != DEF_NULL)
{
    newNode->ID=-1;
    newNode->TCB=-1;
    newNode->next = DEF_NULL;

    if(!head) head = newNode;
    else tail->next = newNode;      
}   
}

LL * getLastNode(LL * head)
{
    LL *temp = head;
    while(temp->next != DEF_NULL)
    {
        temp = temp->next;
    }
    return temp;
}

CPU_INT32U countLL(LL * head)
CPU_INT32U countLL(LL * head)
{
    CPU_INT32U elements = 0;
    LL * temp = head;
    while(temp->next != DEF_NULL)
    {
        temp = temp->next;
        elements++;
    }
    return elements;
}

void addLL(LL * head)
{
LL *newNode;
LL *tail = getLastNode(head);

newNode = malloc(sizeof(LL));
if(newNode != DEF_NULL)
{
    newNode->ID=-1;
    newNode->TCB=-1;
    newNode->next = DEF_NULL;

    if(!head) head = newNode;
    else tail->next = newNode;      
}   
}

LL * getLastNode(LL * head)
{
    LL *temp = head;
    while(temp->next != DEF_NULL)
    {
        temp = temp->next;
    }
    return temp;
}

CPU_INT32U countLL(LL * head)
CPU_INT32U countLL(LL * head)
{
    CPU_INT32U elements = 0;
    LL * temp = head;
    while(temp->next != DEF_NULL)
    {
        temp = temp->next;
        elements++;
    }
    return elements;
}

So here is how I call the function :

LL* list;

addLL(list);
int count = countLL(list);
Debug_LOG("LL count: %i", count);

LL* list;

addLL(list);
int count = countLL(list);
Debug_LOG("LL count: %i", count);

LL* list;

addLL(list);
int count = countLL(list);
Debug_LOG("LL count: %i", count);

LL* list;

addLL(list);
int count = countLL(list);
Debug_LOG("LL count: %i", count);

Please help me spot where I went wrong?

steffenAPP•5/13/24, 4:21 PM

First thing I see is that you do not initialize LL* list to NULL. This means it points to a random address in memory. And that is why the if(!head) check does not work as you would expect

Marvee AmasiAPP•5/13/24, 4:21 PM

@steffen
Thank you, that makes a lot of sense! So, if I initialize list to NULL before calling addLL like this:

 LL* list = NULL;
addLL(list);

 LL* list = NULL;
addLL(list);

This is what you mean?

Marvee AmasiAPP•5/13/24, 4:22 PM

So @steffen I am curious to know how a non-null list before the first addLL call affects the behavior?
Does it create an empty list or point to some unintended memory location?

ZacckOsiemoAPP•5/13/24, 4:22 PM

The latter

ZacckOsiemoAPP•5/13/24, 4:22 PM

it points to a random location.

ZacckOsiemoAPP•5/13/24, 4:23 PM

its indeterminate when you declare a value but dont initialize it.

Marvee AmasiAPP•5/13/24, 4:23 PM

Okay @ZacckOsiemo , Are there any common pitfalls I should be aware of when working with linked lists in C, especially regarding memory management?
@steffen @Middleware & OS @ZacckOsiemo