Why do these code snippets behave differently? - c

Question

I am relatively new to C, and have been learning about linked lists with pointers.
I learned that
(*foo).bar is the same ad foo->bar.
foo->bar is used because it is more readable.
Therefore I do not understand why these code snippets behave differently:
1)
void appendCourse(CourseNode** pLL, Course c){
CourseNode * root = *pLL;
CourseNode* last = makeCourseNode(c);
if(root != NULL){
CourseNode node = *root;
while(node.pNext != NULL){
node = *node.pNext;
}
node.pNext = last;
} else {
*pLL = last;
}
}
and
2)
void appendCourse(CourseNode** pLL, Course c){
CourseNode * root = *pLL;
CourseNode* last = makeCourseNode(c);
if(root != NULL){
CourseNode *node = root;
while(node->pNext != NULL){
node = node->pNext;
}
node->pNext = last;
} else {
*pLL = last;
}
}
to me it looks like 1) should behave as if dereferencing first, then member access. Sort of like (*foo).bar
but 1) doesn't seem to work right at all, it can only successfully add the first element.
2) does however add all elements into the linked list.
In case this helps: my structs and other method:
typedef struct CourseNode {
struct CourseNode* pNext;
Course course;
} CourseNode;
typedef struct
{
StudentNode *pWaitlistHead; // Waitlist for this course
char szCourseId[12]; // Course Identifier
char szRoom[15]; // Room number of the course
char szDays[15]; // What days the course will meet, ex: MWF, TR, etc
char szTimes[15]; // Meeting Time, ex: 10:00-11:15am
int iAvailSeats; // Number of available seats in the course
double dFee; // Additional fees for the course
} Course;
CourseNode* makeCourseNode(Course c){
CourseNode * node = malloc(sizeof(CourseNode));
node->pNext = NULL;
node->course = c;
return node;
}

Answer 1

CourseNode node = *root;
while(node.pNext != NULL){
node = *node.pNext;
}
This creates a new CourseNode called node. The value of that new CourseNode is modified, but that has no affect on the linked list.
CourseNode *node = root;
while(node->pNext != NULL){
node = node->pNext;
}
Here, node points to a CourseNode that is on the linked list.
The simplest way to understand the difference is that the first code excerpt creates new CourseNodes. It's like the difference between these two:
int foo (int *i)
{
int *j = i; // j is a pointer to the same int i points to
*j = 2; // this changes the value of the int i points to
int j = *i; // this creates a new int
j = 2; // this changes the value of that new int
}