segmentation fault

[sarahnade]

Alrighty, my first post. Here we go.

This is my code:

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

typedef struct node {
char *str;
struct node *next;
}node;

typedef struct List {
node *head;
}List;


List l1, l2;


void add(List strList, char *string){
if(strList.head != NULL){
strList.head->next = strList.head;
}
strList.head->str = string;
printf("\n%s\n", strList.head->str);
}
... etc etc


It compiles without a problem, but gives me a segmentation fault when I run it. Through endless "printf("\nklsdfjkl\n");" I've found the problem is in the "strList.head->str = string;". I know it has to to with memory and the *str array in the list nodes, but I don't know how to fix it. If I try to put "char *str = (char *)malloc(80 * sizeof(char));" in the struct, it gives a lot of wierd errors all over the place. Any help would be appreciated. Thanks!

 

[cpjust]

My guess would be that you didn't initialize the List.head and/or node.str and/or node.next pointers to NULL somewhere and then tried to use them.

 

[ArkM]

See also your add() prototype:

void add([b]List strList[/b], char *string);
/* instead of List* */

strList structure passed by value so you lost all argument link pointer modifications. In othen words, the function does nothing.

 

[Salem]

> if(strList.head != NULL)
Use a temp pointer to traverse from the head of the list to the tail (the tail being the node where ptr->next == NULL)

Then you need to
- allocate a new node
- allocate a string (don't forget to count the \0)
- append the new node to the end of the list
- copy the input string to the node.

--

 

[sarahnade]

Thanks so much! I got it. Yall are great.