Segmentation Fault in Loop's Condition - c++

Question

The following code is to sort a linked list after creating it. The sorting algorithm used is somewhat similar to Bubble Sort. I am checking the two consecutive nodes and swapping them if necessary. I used the debugger which told me that the fault is raised while condition checking for the loops which are used while sorting.
#include<iostream>
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<conio.h>
using namespace std;
struct link_list
{
char value[20];
struct link_list *next;
};
int main()
{
struct link_list *head=NULL;
int i,j;
char input[20];
char ch;
struct link_list *loop_var,*temp2,*prev_node,*temp4=NULL;
temp3=NULL;
do
{
cout<<"\nEnter the string you want to insert";
cin>>input;
cout<<"\nDo you want to continue entering?";
cin>>ch;
if (head==NULL)
{
head=new link_list;
strcpy(head->value,input);
head->next=NULL;
continue;
}
for (loop_var=head;loop_var->next!=NULL;loop_var=loop_var->next);
temp2=new link_list;
loop_var->next=temp2;
strcpy(temp2->value,input);
temp2->next=NULL;
}while(ch=='y' || ch=='Y');
for (loop_var=head;loop_var->next!=NULL;loop_var=loop_var->next)
{
cout<<loop_var->value<<"\n";
}
cout<<loop_var->value<<"\n";
char arr[20];
for (loop_var=head;loop_var->next!=NULL;loop_var=loop_var->next)
{
cout<<"\nLoop1";
for (temp4=head;temp4->next!=NULL;temp4=temp4->next)
{
cout<<"\nLoop2";
temp2=temp4;
if (strcmp(temp2->value,temp2->next->value)>0)
{
cout<<"\nSwap Enter";
if (temp2==head && temp2->next->next==NULL)
{
cout<<"\nSpecial1";
temp2->next->next=temp;
temp2->next=NULL;
}
else if (temp2==head)
{
cout<<"\nSpecial2";
head=temp2->next;
temp2->next=head->next;
head->next=temp2;
}
else if (temp2->next->next==NULL)
{
cout<<"\nSpecial3";
prev_node->next=temp2->next;
prev_node->next->next=temp2;
temp2->next=NULL;
}
else
{
cout<<"\nNormal1";
prev_node->next=temp2->next;
temp2->next=prev_node->next->next;
prev_node->next->next=temp2;
cout<<"\nNormal2";
}
}
prev_node=temp4;
cout<<"\nLoop2PreExit";
fflush(stdin);
cout<<"\nLoop2Exit";
}
cout<<"\nLoop1Exit";
}
for (loop_var=head;loop_var->next!=NULL;loop_var=loop_var->next)
{
cout<<loop_var->value<<"\n";
}
cout<<loop_var->value;
getch();
}

Answer 1

temp2->next->next=temp;
"temp" is not defined anywhere... if your compiler filled in that hole for you, then this is what is causing your loop's condition to segfault.
Also, naming every other variable "temp#" is an easy way to have mistakes like this.