Thread: help with trees

need some help with trees, basically I'm building a tree of people with names and phone numbers which will then be searched, however i keep having problems with the insert function which causes segmentation faults.

i fear this could be something wrong with my pointers, but some help would be very much appreciated

Code:

#include <stdlib.h>
#include <ctype.h>
#include <stdio.h>

typedef struct {
        char name[255];
        char number[255];
        } entry;

typedef struct tree {
        entry *thisnode;
        struct tree *left;
        struct tree *right;
        } Tree ;
        
Tree *makenode(entry *p, Tree *l, Tree *r ) {
     Tree *t = malloc( sizeof( Tree ) ) ;
     t->left = l;
     t->right = r;
     strcpy(t->thisnode->name, p->name);
     strcpy(t->thisnode->number, p->number);
     return t;
}

Tree *insert(Tree *root, entry *what ) {
     if( root == NULL ) {
         root = makenode(what, NULL, NULL);
     } else if(strcmp(what->name, root->thisnode->name) < 0 ) {
         root->left = insert( root->left, what ) ;
     } else {
         root->right = insert( root->right, what ) ;
     }
     return root ;
}

int main( void ) {
    entry *e;
    Tree *tree = NULL;
    do {
       scanf("%s", e->name);
       if( strcmp(e->name, "." ) != 0 ) {
           scanf("%s", e->number);
           tree = insert(tree, e);
       }
    } while( strcmp( e->name, "." ) != 0 ) ;
    return 0;
}