Question

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

struct node {
    char str[200];
    int nn;
    struct node* next;
};

int number;
struct node* start=NULL;
struct node* current;
//function to insert into the list 

void insert() {
    struct node* n;
    n=(struct node*)malloc(sizeof(struct node));
    n->str=malloc(sizeof(char) * 1000);
    printf("please enter the data that you would like to insert: ");
    gets(n->str);
    printf("asdasdasdasd");
    n->next=NULL;
    if( start==NULL ) {
        start->next=n;
        current=n;
    }
    else {

    current->next=n;
    current=n;

    }

    printf("done\n");
}

void display() {
    current=start;
    int i=0;
    while( current->next!=NULL ) {
        printf("node%d= %s\n",++i,current->str);
        current=current->next;

    }
    printf("this the end");
}


int main() {
    char c;
    int input;

    do {
        printf("Select from the following options:\n"
           "1.Display list\n"
           "2.Add to list\n"
           "3.delete from list\n");

        scanf("%d",&input);
        switch (input) {
            case 1: display(); break;
            case 2: insert(); break;
      //    case 3: delete(); break;
            default : printf("Please select 1 , 2 or 3\n");
        }
        printf( "would you like to continue?(y/n)\n");
        scanf("%s",&c);
    } while(c=='y');

    return 0;
}

This is giving me an error in the insert function, A SEGMENTATION FAULT !

I Tried things but I just don’t get the clear picture. I am a bit weak with pointers, actually confused !

Please help me out by telling me what I am doing wrong. Forget about my linked list logic, let it be wrong. I just wanna know why a segmentation fault is occurring !

Answer 1

you have many mistakes, but your crash is because you don’t allocate start

n->next=NULL;
    if( start==NULL ) {
        start->next=n;
        current=n;
    }
    else {

    current->next=n;
    current=n;

you ask if start is null, and if it is you try to read it by calling start->next it. you need to allocate it first.