CODEWITHSUNDEEP
c
lizardbrush
lizardbrush

Reputation: 1

Program crashes when trying to return pointer to linked list

I'm trying to return a pointer to a linked list to main so that I can pass it around to other functions.Anytime I try to get load to pass anything the program crashes and it messes up the file output.I just can't figure out why.

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

struct list{                //creating linked list
 char furn[128];
 int priority;
 struct list *next;
           };
 typedef struct list List;   //typedef for list
              //creating pointer for head of list

List **Load();
int main(List **points)

{
  points->Load();               //crashes here no if I try to set Load to anything, works fine and prints okay if I don't





}
List ** Load()

{    List *head;
     List *current;                        //so we can build and navigate list
    List *new;
    FILE *fin, *fout;                     //so that we can start file manipulation
    char name[]= "California.txt" ;
    fin=fopen(name, "r");
    new=malloc((sizeof(List)));    //creating list
    head=new;
while(current->next!=NULL)
    {
        current=new;
        new=malloc((sizeof(List)));
        fscanf(fin,"%s %d",current->furn,&current->priority);    //reading and populating list
        current->next=new;


    if(feof(fin))
        current->next=NULL;

   }
   current=head;
   printf("%s %d",current->furn,current->priority);
 while(current->next!=NULL)
   {
        printf("Starting");
       printf("%s %d",current->furn,current->priority);
       current=current->next;
   }
   List **points=&head;
   return points;    //Returning so we can have a pointer to the list

   }

Upvotes: 0

Views: 186

Answers (2)

lizardbrush
lizardbrush

Reputation: 1

I figured out an answer. I wasn't allocating memory in main so something was happening to it when I tried to pass the pointer. After I allocated it in main I was able to create a double pointer that points to the address of the first pointer and then pass that around. Manipulating the linked list by dereferencing my double pointer (*pointer)->item. Thanks for the help I got the idea from here.

Upvotes: 0

tom
tom

Reputation: 1313

int main(List **points)

does not work. It should be:

int main(int argc, char *argv[])

See main(int argc, char *argv[]) or What should main() return in C and C++? for more details.

points->Load();

does not work - if your function Load returns a pointer then it should be: 

points=Load();

I think there is also an issue with you repeated use of malloc in the loop in the function. It seems to me that you want a long list, but I think it will be impossible to free all the memory you have allocated at the end of the program, because you only return the address of head.

Upvotes: 1

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