sorted linked list...why seg faults!

[S15_88]

i have a program that adds a name and an age to a structure then that structure is added to a list that's sorted by name and age.

when i add a struct then go to remove it, seg fault!

when i add a struct it's all good but when i go to add another struct, seg fault!

i'm using -g when compiling and valgrind --show-reachable=yes to see the problems with memory.

i can't figure this out for the life of me, can someone shed some light on as to why i'm getting these seg faults.

Thanks, ALain


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

#define MAX_LEN 250

typedef struct node
{
char *name;
int age;
struct node *nextName;
struct node *nextAge;
}NODE;

int drain_stdin()
{
int c;

while((c = getchar()) != '\n' && c != EOF);

return c;
}

NODE * listInput(NODE *new)
{

new = malloc(sizeof(NODE));
new->name = malloc(sizeof(char)*MAX_LEN + 1);

if (drain_stdin() != EOF)
{
printf("Enter name: ");
fgets(new->name, MAX_LEN + 1, stdin);

printf("Enter age: ");
scanf("%d", &new->age);
}
else
{
printf("An Error Has Occured\n");
}
return new;
}

NODE * insertNameNode(NODE *new, NODE *head1)
{
NODE *temp;
NODE *prev;

new->nextName = NULL;

if (head1 == NULL)
{
return new;
}

temp = head1;
prev = NULL;

while(1)
{
if (strcmp(temp->name, new->name) < 0)
{
prev = temp;
temp = temp->nextName;
continue;
}
else/* if(strcmp(temp->name, new->name) >= 0) */
{
new->nextName = temp;

if (prev != NULL)
{
prev->nextName = new;
}
else
{
head1 = new;
/*break;*/
}
}
}
return (head1);
}

NODE * insertAgeNode(NODE *new, NODE *head2)
{
NODE *temp;
NODE *prev;

new->nextAge = NULL;

if (head2 == NULL)
{
return new;
}

temp = head2;
prev = NULL;

while(1)
{

if (temp->age < new->age)
{
prev = temp;
temp = temp->nextAge;
continue;
}
else/* if(temp->age >= new->age) */
{
new->nextAge = temp;

if (prev != NULL)
{
prev->nextAge = new;
}
else
{
head2 = new;
/* break;*/
}
}
}
return(head2);
}


NODE * removeNameStruct(NODE *head1, char *nameRemove)
{
NODE *prev;
NODE *root;

prev = NULL;
root = head1;

if (drain_stdin() != EOF )
{
printf("Enter Name Of Desired Record To Be Removed: ");
fgets(nameRemove, MAX_LEN + 1, stdin);

while (root != NULL)
{
if(strcmp(nameRemove, root->name) == 0)
{
printf("Found The Record\n");

if (prev != NULL)
{
prev->nextName = root->nextName;
}
else
{
head1 = root->nextName;
}
root = root->nextName;
/*free(head1);*/
break;
}
else
{
printf("Record NOT Found\n");
prev = root;
root = root->nextName;
}
}
}
else
{
printf("An Error Has Occured\n");
}
return (head1);
}

NODE * removeAgeStruct(NODE *head2, char *nameRemove)
{

NODE *prev;
NODE *root;

prev = NULL;
root = head2;

while (root != NULL)
{
if(strcmp(nameRemove, root->name) == 0)
{
printf("Found The Record\n");

if (prev != NULL)
{
prev->nextAge = root->nextAge;
}
else
{
head2 = root->nextAge;
}
root = root->nextAge;
free(head2->name);
free(head2);
break;
}
else
{
printf("Record NOT Found\n");
prev = root;
root = root->nextAge;
}
}
return (head2);
}

void printName(NODE *head1, NODE *head2)
{
if (head1 == NULL)
{
printf("List is empty.\n") ;
return;
}
else
{
while (head1 != NULL)
{
printf("%s %d\n", head1->name, head1->age);
head1 = head1->nextName;
}
}
}

void printAge(NODE *head1, NODE *head2)
{
if (head2 == NULL)
{
printf("List is empty.\n") ;
return ;
}
else
{
while (head2 != NULL)
{
printf("%s %d\n", head2->name, head2->age);
head2 = head2->nextAge;
}
}
}


void freeProg(NODE *head1, NODE *head2)
{
/*
while(head1 != NULL && head2 != NULL)
{
free(head2->name);
free(head2);
}
*/
}


int main(void)
{
int choice, count;
char nameRemove[MAX_LEN + 1];

choice = 0;
count = 0;

NODE *new;
NODE *head1;
NODE *head2;

new = NULL;
head1 = NULL;
head2 = NULL;

do
{
printf("1. Add structure\n");
printf("2. Remove structure\n");
printf("3. Print names\n");
printf("4. Print ages\n");
printf("5. Exit\n");
scanf("%d", &choice);

if(choice == 1)
{
new = listInput(new);
head1 = insertNameNode(new, head1);
head2 = insertAgeNode(new, head2);
}
else if(choice == 2)
{
head1 = removeNameStruct(head1, nameRemove);
head2 = removeAgeStruct(head2, nameRemove);
}

else if(choice == 3)
{
printName(head1, head2);
}
else if(choice == 4)
{
printAge(head1, head2);
}
else if(choice == 5)
{
freeProg(head1, head2);
}
else
{
return 0;
}

}while(choice != 5);

return 0;
}

/*
NODE * removeStruct(NODE *head1, NODE *head2)
{
NODE *prev;
NODE *root;

prev = NULL;
root = head1;

char nameRemove[MAX_LEN + 1];

if (drain_stdin() != EOF )
{
printf("Enter Name Of Desired Record To Be Removed: ");
fgets(nameRemove, MAX_LEN + 1, stdin);

while (head1 != NULL)
{
if(strcmp(nameRemove, root->name) == 0)
{
printf("Found The Record\n");
if (prev != NULL)
{
prev->nextName = head1->nextName;

}
else
{
root = head1->nextName;

}
free(head1);
break;
}
else
{
prev = head1;
head1 = head1->nextName;
}
}
}
else
{
printf("An Error Has Occured\n");
}
return head1;
}
*/

[kknd]

Try debugging it with gdb.

[Jessehk]

A linked list node, regardless of how many pieces of data it has, only contains one link to the next node.

Your code,

typedef struct node
{
char *name;
int age;
struct node *nextName;
struct node *nextAge;
}NODE;


is nonsensical.

You didn't look at the linked list guide I gave you last time this happened, did you?

[themusicwave]

A linked list node, regardless of how many pieces of data it has, only contains one link to the next node.

Your code,

typedef struct node
{
char *name;
int age;
struct node *nextName;
struct node *nextAge;
}NODE;


is nonsensical.

You didn't look at the linked list guide I gave you last time this happended, did you?

The only time you need more than one link is perhaps for a doubly linked list where you can traverse forwards and backwards. For starters, I would only worry about going through the list forwards unless you need to go backwards.

Either way though, you need to link to nodes not to the data they contain.

[Jessehk]

only contains one link to the next node.


:)

[WW]

A linked list node, regardless of how many pieces of data it has, only contains one link to the next node.

Your code,

typedef struct node
{
char *name;
int age;
struct node *nextName;
struct node *nextAge;
}NODE;


is nonsensical.

I beg to differ. There is no reason this can't work. S15_88 is implementing two linked lists, that happen to hold the same data. I'm not saying that this implementation is great, but it is not "nonsensical".

S15_88: Your "insert" functions are more complicated than necessary. Check out these versions:

NODE * insertNameNode(NODE *new, NODE *head1)
{
NODE *temp;
NODE *prev;

temp = head1;
prev = NULL;
while ((temp != NULL) && (strcmp(temp->name,new->name) < 0))
{
prev = temp;
temp = temp->nextName;
}
new->nextName = temp;
if (prev == NULL)
{
// Special case: new becomes the first element in the list.
return new;
}
else
{
prev->nextName = new;
return head1;
}
}

NODE * insertAgeNode(NODE *new, NODE *head2)
{
NODE *temp;
NODE *prev;

temp = head2;
prev = NULL;
while ((temp != NULL) && (temp->age < new->age))
{
prev = temp;
temp = temp->nextAge;
}
new->nextAge = temp;
if (prev == NULL)
{
// Special case: new becomes the first element in the list.
return new;
}
else
{
prev->nextAge = new;
return head2;
}
}