Question

I built a stack data structure, which has a peek method. The compiler is giving me a warning: initialization makes pointer from integer without a cast warning when calling peek in main. Here is what I have:

stack.h:

struct stack_elem {
    struct stack_elem *next;
};

struct stack {
    struct stack_elem *top;
};

void stack_init(struct stack *stack);
int isEmpty(struct stack *);
struct stack_elem * peak(struct stack *);

And its implementation:

void stack_init(struct stack *stack) {
    stack->top = NULL;
}

int isEmpty(struct stack *stack) {  
    if (stack->top == NULL) 
        return 1;
    else
        return 0;
}

struct stack_elem * peek(struct stack *stack) { 
    if (isEmpty(stack) == 1)  
        return NULL;
    else
        return stack->top;
}

In my main.c, I define stack as follows:

struct stack stack;
stack_init(&stack);

and call peek:

struct stack_elem * elem = peek(&stack);

This line throws the warning. The weird thing here is that I used to import stack.c into main.c and just compile with $ gcc main.c. This had absolutely no errors. Now I changed the import to stack.h, and I am compiling with $ gcc main.c stack.c which throws the warnings. Running it also segfaults (which it didn’t beforehand).

Answer 1

Change:

struct stack_elem * peak(struct stack *);

To:

struct stack_elem * peek(struct stack *);

: )