building a linked list from tree leaf nodes

hii , I'll appreciate it if someone please help me with this problem
I want to create a linked-list from the leaves of a tree ordered from right to left .
without using a Static or global variable

typedef struct t_node {
int data;
struct t_node *left;
struct t_node *right;
} T_NODE;


typedef struct list_node
{
int data;
struct list_node *next;
} L_NODE;

the function header : L_NODE* leavesRightToLeft (T_NODE* root, 1 more variable )
for example :

Code:

---

                                  3
                                /    \
                              2      5
                              \    /  \
                                4  7  9
                                        /
                                      1

---

and the function will return a pointer to linked list that will be as following :
1 -> 7 -> 4