C Program: Create Linked List Using argv, argc, Segmentation Fault

Question

I have a program that takes in strings using the command line prompts argv and argc. I keep getting a segmentation fault when I go to run the code and after much researching, I cannot determine what might be causing this. Maybe how I execute the code is the issue? I am using gcc -o code code.c then ./code one two three with one two three being the strings added to the linked list. Any assistance in determining where my error might be would be great.

Here is my code:

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

typedef struct list_node_s{
    char the_char;
    struct list_node_s *next_node;
}list_node;

void insert_node(list_node *the_head, char the_char);
void print_list(list_node *the_head);

int main(int argc, char *argv[]){
    char next_char;
    list_node *the_head = NULL;
    insert_node(the_head, next_char);
    the_head->next_node = malloc(sizeof(list_node));
    if(the_head == NULL){
            return 1;
    }

    the_head->the_char = 1;
    the_head->next_node == NULL;
    int the_count, the_count2;
    for(the_count = 0; the_count < sizeof(argv); the_count++){
            for(the_count2 = 0; argv[the_count][the_count2] != '\0'; the_count2++){
                    next_char = argv[the_count][the_count2];
                    insert_node(the_head, next_char);
            }
    }

    print_list(the_head);
    return (0);
}

void insert_node(list_node *the_head, char the_char){
    list_node * current_node = the_head;
    while (current_node->next_node != NULL) {
        current_node = current_node->next_node;
    }

    current_node->next_node = malloc(sizeof(list_node));
    current_node->next_node->the_char = the_char;
    current_node->next_node->next_node = NULL;
}

void print_list(list_node *the_head){
    if(the_head == NULL){
            printf("\n");
    }else{
            printf("%c", the_head->the_char);
            print_list(the_head->next_node);
    }

}

Answer 1

Change this:

list_node *the_head = NULL;
insert_node(the_head, next_char);
the_head->next_node = malloc(sizeof(list_node));

to:

list_node the_head = { '\0', NULL };

to initialize the_head to an empty node.