In C I am getting segmentation fault, i do not know why

Question

I am making a Binary Search Tree that stores Multiple things in one instance, I have two errors That I ran into. The first one that happens in the function insert use to work in than randomly it stopped, the second one is in print_tree_inorder and I have no idea why that would be broken.

#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
#include <stdbool.h> 
#include <string.h>
#include <malloc.h>


char* nameArray[50] = {};
char* number[50] = {};
char* ID[50] = {};
char* hours[50] = {};
char* pPH[50] = {};
int flag;
typedef struct node
{

    char* name;
    char* phoneNum;
    char* ID;
    char* hours;
    char* pPH;
    struct node * left;
    struct node * right;
} node_t;




void insert(node_t * tree, char* name, char* phoneNum, char* hours, char* pPH);
void print_tree_inorder(node_t * current);

int main()
{
    char* n,p,id,h,pph;
    int numberOfTimes = 0;

    node_t * test_list = malloc(sizeof(node_t));

    /* set values explicitly, alternative would be calloc() */
    test_list->name =  "";
    test_list->phoneNum = "";
    //test_list->ID = "";
    test_list->hours = "";
    test_list->pPH = "";


    test_list->left = NULL;
    test_list->right = NULL;
    printf("Please enter in the amount of people you want: ");
    scanf("%d",&numberOfTimes);
    printf("\n");

         for(int i = 0; i<numberOfTimes; i++){
             printf("Please enter in name: ");
             scanf("%s", &n);
             nameArray[i] = n; 

             printf("Please enter in PhoneNumber: ");
             scanf("%s", &p);
             number[i] = p;
             printf("Please enter in Hours: ");
             scanf("%s", &h);
             hours[i] = h;
             //printf("\n");
             printf("Please enter in pay per hour: ");
             scanf("%s", &pph);
             pPH[i] = pph;


            insert(test_list,nameArray[i],number[i],hours[i], pPH[i] );

        }

    printf("\n In order\n");
    print_tree_inorder(test_list);
}

void insert(node_t * tree, char* name, char* phoneNum,  char* hours, char* pPH)
{  
    //unsigned int number = (unsigned int)ptr

    if (tree->name == 0)
    {
        /* insert on current (empty) position */
        tree->name = name;
        tree->phoneNum = phoneNum;
        //tree->ID = ID;
        tree->hours = hours;
        tree->pPH = pPH;
    }
    else
    {

        if ( strcmp(tree->name, name) > 0)
        {
            /* insert left */
            if (tree->left != NULL)
            {
                insert(tree->left, name, phoneNum, hours, pPH);
            }
            else /* no left nodes*/
            {
                tree->left = malloc(sizeof(node_t));
                /* set values explicitly, alternative would be calloc() */
                tree->left->name = name;
                tree->left->phoneNum = phoneNum;

                tree->left->hours = hours;
                tree->left->pPH = pPH;
                tree->left->left = NULL;
                tree->left->right = NULL;
            }
        }
        else /*add node to right */
        {
            if ( strcmp(tree->name, name) <= 0)
            {
                /* insert right */
                if (tree->right != NULL)
                {
                    insert(tree->right, name, phoneNum,  hours, pPH);
                }
                else
                {
                    tree->right = malloc(sizeof(node_t));
                    /* set values explicitly, alternative would be calloc() */
                    tree->right->name = name;
                    tree->right->phoneNum = phoneNum;

                    tree->right->hours = hours;
                    tree->right->pPH = pPH;
                    tree->right->left = NULL;
                    tree->right->right = NULL;
                }
            }
        }
    }

}

void print_tree_inorder(node_t * current) {
    if (current == NULL) return;
    print_tree_inorder(current->left);
    printf(" %s %s %s %s\n", current->name, current->phoneNum,current->hours, current->pPH);

    print_tree_inorder(current->right);
}

Answer 1

Several problems in your code. First of all you should not include malloc.h. It is deprecated.

Looks like there is some confusion around the declaration of n,p,id,h,pph variables. This statement:

char* n,p,id,h,pph;

declares only n as of type char * and rest of the variables p,id,h,pph declared as of type char.

Lets talk about the warnings reported by the compiler (I am using gcc compiler and providing -Wall and -Wextra options during compilation):

$ gcc -Wall -Wextra prg.c 
prg.c:56:26: warning: format specifies type 'char *' but the argument has type 'char **' [-Wformat]
             scanf("%s", &n);
                    ~~   ^~
prg.c:61:24: warning: incompatible integer to pointer conversion assigning to 'char *' from 'char'; take the address with & [-Wint-conversion]
             number[i] = p;
                       ^ ~
                         &
prg.c:64:23: warning: incompatible integer to pointer conversion assigning to 'char *' from 'char'; take the address with & [-Wint-conversion]
             hours[i] = h;
                      ^ ~
                        &
prg.c:68:21: warning: incompatible integer to pointer conversion assigning to 'char *' from 'char'; take the address with & [-Wint-conversion]
             pPH[i] = pph;
                    ^ ~~~
                      &
prg.c:35:15: warning: unused variable 'id' [-Wunused-variable]
    char* n,p,id,h,pph;
              ^
5 warnings generated.

You should not ignore the compiler warning messages. They are there for some reason.

Warning 1:
n is of type char * and therefore &n is of type char **. The %s format specifier in scanf() expects the argument as an array and the array must have room for at least input_size+1 characters.

You should declare n as array of characters, something like this:

char n[50];
// and for input
scanf("%49s", n);

Warning 2:

p is of type char and number[i] is of type char *. Hence the assignment is incompatible. Also the &p is of type char *, thats why the compiler is not reporting any warning on statement:

scanf("%s", &p);

But this is not correct because p is of type char and it does not have enough room for the string input. Read more about format specifiers of scanf().

You can do:

char p[50];
// and for input
scanf("%49s", p);
number[i] = strdup(p);

If you do not use strdup, all the pointers of number array end up pointing to same location. Alternatively, you can declare p as char * and explicitly handle the memory allocation/deallocation operation. Make sure to free the memory returned by strdup, once you are done with it. Same explanation for warning 3 and 4.

Warning 5:
Remove the unused variables from your code.

There is a scope of improvement in your code. Try to figure out them by yourself.