linked list and damn on linked list

[St0rM-MaN]

hi all
i really hate this damn thing

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

struct info
{
        int x;
        struct info *next;
};

int main()
{
        struct info *root;
        struct info *new;
        int v=0;
        root=malloc(sizeof(struct info));
        new->next=malloc(sizeof(struct info));
        new=new->next;
        while(new!=0)
        {
                new->x=5;
                new->next=malloc(sizeof(struct info));
                new=new->next;
                v++;
                if(v==5)
                {
                        new->next=0;
                        new=new->next;
                }
        }

        new=root;
        while(new!=0)
        {
                printf("%d\n",new->x);
                new=new->next;
        }
return 0;
}

it keep telling me

Segmentation fault

it should initialize x to 5 for 5 times

my question is
why it's not working ?

[FillYourBrain]

This line:
new->next=malloc(sizeof(struct info));

"new" has nothing allocated

[St0rM-MaN]

new->next=malloc(sizeof(struct info));
new=new->next;

new is pointing to the allocated space
i can't understand it

[itsme86]

Where is new pointing to allocated space? What are you smoking?

[robwhit]

root->next is not initialized. all the new allocations are leaked.

[ssharish2005]

look first of all you shouldn't have used a 'new' word as your variable. Since it is a keyword, but anyway.

You can see that new has been declared as a pointer of type struct info * but not as a struct info. Which mean it can hold just the address of the struct info. So when you do this

new->next

The new is no where pointing but you still dereference the struct elements which is not right and which is giving u SF.

Allocate memory for new first and then dereference the new. This would give you some progress.

ssharish2005

[St0rM-MaN]

look first of all you shouldn't have used a 'new' word as your variable. Since it is a keyword, but anyway.

You can see that new has been declared as a pointer of type struct info * but not as a struct info. Which mean it can hold just the address of the struct info. So when you do this

new->next

The new is no where pointing but you still dereference the struct elements which is not right and which is giving u SF.

Allocate memory for new first and then dereference the new. This would give you some progress.

ssharish2005

you mean for example
[code]
new= malloc(sizeof(struct info));
new->next=new;
head=new
[code]

[St0rM-MaN]

Where is new pointing to allocated space? What are you smoking?

nothing i wish i can smoke

[ssharish2005]

new= malloc(sizeof(struct info));
new->next=new; // you should perhaps need new->next=NULL, other wise u will end up 
with the infinite loop when u print
head=new

ssharish2005

[St0rM-MaN]

how about this one

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

struct info
{
        int x;
        struct info *next;
}h;
int main()
{
        struct info *head;
        struct info *current;
        int g=0;
        head=&h;

        current=malloc(sizeof(struct info));
        current->next=current;
        while(current!=0)
        {
                current->x=5;
                current->next=malloc(sizeof(struct info));
                current=current->next;
                g++;
                if(g==5)
                {
                        current->next=0;
                        current=current->next;
                }

        }
current=head;

while(current!=0)
{
        printf("&#37;s\n",current);
        current=current->next;
}
return 0;
}

but it's not printing any value just a new line

[St0rM-MaN]

new= malloc(sizeof(struct info));
new->next=new; // you should perhaps need new->next=NULL, other wise u will end up 
with the infinite loop when u print
head=new

ssharish2005

i will try it now
thanks for your help

[St0rM-MaN]

daaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaamn
it finally works

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

struct info
{
        int x;
        struct info *next;
}h;
int main()
{
        struct info *head;
        struct info *current;
        int g=0;

        current=malloc(sizeof(struct info));
        current->next=current;
        head=current;
        while(current!=0)
        {
                current->x=5;
                current->next=malloc(sizeof(struct info));
                current=current->next;
                g++;
                if(g==5)
                {
                        current->next=0;
                        current=current->next;
                }

        }
current=head;

while(current!=0)
{
        printf("&#37;d\n",current->x);
        current=current->next;
}
return 0;
}

thanks ssharish2005

[St0rM-MaN]

i guess i finally under stand it
current is a pointer from type struct *info
we allocate space for this pointer to hold the data in the struct
then we
current->next=current witch points to the first data in the structure
then we
head=current
to make head points to the first memory location for the list

|IS this Right ??| if not would somebody pleas fix it
thanks all

[itsme86]

Your description is right, but your logic is flawed. What would head->next end up pointing to? head. This makes an infinite loop which is probably not what you want (there are some applications for that, but probably not this instance).

Instead of doing:

current->next = current;

Try this:

current->next = NULL;