C : Singly linked list sorting segmentation fault

Question

void List_sort (struct nodeStruct **headRef){
    struct nodeStruct *tempNode = *headRef;
    struct nodeStruct *nextNode, *smallestNode;
        while (tempNode != NULL){
            nextNode = tempNode->next;
            smallestNode = tempNode;
            while (nextNode != NULL){
                if (nextNode->item < smallestNode->item) {
                    smallestNode = nextNode->next;
                }
                nextNode = nextNode->next;
            }
            int tempInt = tempNode->item;
            tempNode->item = smallestNode->item;
            smallestNode->item = tempInt;
            tempNode = tempNode->next;
        }   
}

Don't know why it's generating a seg fault, there should be no edits to NULL. Segmentation fault. 0x00000000004008d4 in List_sort (headRef=0x7fffffffe458) at list.c:130 130 tempNode->item = smallestNode->item; Anyone know why it's doing this?

Update: Performed the suggestions and no more seg fault, however does not sort correctly.

Value: 1
Value: 2
Value: 7
Value: 3
Value: 4
Value: 6
Value: 5
Value After Sort: 1
Value After Sort: 2
Value After Sort: 4
Value After Sort: 3
Value After Sort: 5
Value After Sort: 6
Value After Sort: 7

the if(tempNode == NULL) {} else {... check before while(tempNode != NULL) is redundant. — user3185968
– user3185968, Commented Jan 26, 2015 at 4:10
in while (nextNode != NULL){ if (nextNode->item < smallestNode->item) smallestNode = nextNode->next;, nextNode->next may be NULL, causing smallestNode to be NULL afterwards. I'd say the offending line should be smallestNode = nextNode instead. — user3185968
– user3185968, Commented Jan 26, 2015 at 4:18
@EOF jesus christ, could not see that small mistake. Thank you — Aaron
– Aaron, Commented Jan 26, 2015 at 4:21
Is there a reason not to close this as 'off-topic, trivial typo'? — Jonathan Leffler
– Jonathan Leffler, Commented Jan 26, 2015 at 4:49

Klas Lindbäck · Accepted Answer · 2015-01-26 08:24:50Z

1

This isn't right:

            if (nextNode->item < smallestNode->item) {
                smallestNode = nextNode->next;
            }

it should be:

            if (nextNode->item < smallestNode->item) {
                smallestNode = nextNode;
            }

answered Jan 26, 2015 at 8:24

Klas Lindbäck

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