Question

I’m trying to implement a stack in C using singly linked lists, it all works fine as long as the stack is non-empty. Once empty my pop method never detects that its empty but gives some random values. Is there any way so that i can know the stack is empty ? Here is the pop method i’m using along with a sample main program output.

int main(int argc, char const *argv[])
{
    Node* top;
    push(&top,5);
    printf("Popped Element: %d\n",pop(&top));
    printf("Popped Element: %d\n",pop(&top));

    return 0;
}

int pop(Node** top)
{
    if(*top == NULL)
    {
        printf("Error: Stack is empty!\n");
        return;
    }
    int temp = (*top)->iData;
    *top = (*top)->next;
    return temp;
}

output:

Popped Element: 5
Popped Element: 1707388

EDIT:
here is the code for push

void push(Node** top ,int num)
{
    Node* temp = (Node* )malloc(sizeof(Node));
    temp->iData = num;
    temp->next = *top;
    *top = temp;
}

Answer 1

initialize next to NULL while creating and adding a new node to the list. and use

return -1;

instead of

return;

Edit:

Initialize *top =NULL in main like

   int main(int argc, char const *argv[])
{
    Node* top=NULL;
    push(&top,5);
    printf("Popped Element: %d\n",pop(&top));
    printf("Popped Element: %d\n",pop(&top));

    return 0;
}