Printing binary search tree, segmentation fault error 11 - c

Question

could you help me?
Program reads words from a file and puts them into binary search tree, but I get "Segmentation fault: 11" when running my print function.
struct node {
char * item;
struct node * left;
struct node * right;
};
struct node * new(char * a) {
struct node * new;
new = (struct node *)malloc(sizeof(struct node *));
new->item = a;
new->left = new->right = NULL;
return new;
}
struct node * insert(struct node * a, char * b) {
if(a == NULL) {
a = new(b);
}
else if (b <= a->item) {
a->left = insert(a->left, b);
}
else {
a->right = insert(a->right, b);
}
return a;
}
void print(struct node * a) {
if (a->left == NULL && a->right == NULL)
printf("%s", a->item);
else if (a->left != NULL)
print(a->left);
else
print(a->right);
}
from main.c :
struct node * root = NULL;
struct node * start;
start = root;
while (fscanf(fp, "%s", temp) != EOF) {
root = insert(root, temp); // insert function works ok
}
print(start);
UPDATE:
I've made a change in main.c:
int i = 0;
while (fscanf(fp, "%s", temp) != EOF) {
root = insert(root, temp);
if (!i) {
start = root;
i = 1;
}
}
Now it doesn't show error, but it prints only the last word from the tree instead of printing it recursively. Any suggestions?
UPDATE #2:
Thank you for your help. Following your suggestions I've made changes to this function:
struct node * new(char * a) {
struct node * new;
char * stringcopy;
stringcopy = malloc(strlen(a) + 1);
strcpy(stringcopy, a);
new = malloc(sizeof(* new));
new->item = stringcopy;
new->left = new->right = NULL;
return new;
}
Now everything works fine.

Answer 1

The original problem was almost certainly that start was NULL since you did not update it when you updated root. (Meanwhile it seems that the whole start is unnecessary; just use root directly.)
The new problem (printing only the last word) is that you are not traversing the tree correctly: your print function only prints if both left and right are NULL, so only a leaf node is ever printed, and furthermore it does not descend into the right branch if there is a left branch.
You could try something like this instead (untested code):
void print(struct node * a) {
if (a == NULL) { return; }
print(a->left);
(void) puts(a->item);
print(a->right);
}
In particular, note that if you are at a non-NULL node, you need to print its item unconditionally, or the complete output will be missing that node.
Another problem seems to be that you are not copying item when you create the node. So if your temp in insert(root, temp) is indeed a temporary object that will be overwritten or freed, all of your items (except possibly the last) will be invalid by the time you try to print them. Instead of assigning new->item = a, do the equivalent of new->item = strdup(a) and then remember to free it when you free the node.
(strdup is not in the C standard library, but it is easy to implement: allocate enough space for the string, including NUL terminator, and copy.)
Also, the comparison b <= a->item is almost certainly not doing what you expect it to; see strcmp.