Stack

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

#define TRUE 1
#define FALSE 0

typedef struct {
    char *key;
    char *value;
} Option;

typedef struct Stack {
    Option option;
    struct Stack *next;
} Stack;

char *strdup (const char *source_str)
{
    char *dest_str = malloc (strlen(source_str) + 1);
    if (dest_str != NULL) strcpy (dest_str,source_str);
    return dest_str;
}

void push_option(Stack **head, char *key, char *value)
{
    Option option = { strdup(key), strdup(value) };

    Stack *stack = malloc(sizeof(Stack));
    stack->option = option;
    stack->next = *head;

    *head = stack;
}

Option pop_option(Stack **head)
{
    Option option = {};
    if (head != NULL) {
        Stack *prevStack;
        prevStack = *head;
        *head = (*head)->next;

        option = prevStack->option;
        free(prevStack);
    }
    return option;
}

void free_option(Option option)
{
    free(option.key);
    free(option.value);
}

int main(void)
{
    Stack *stack = NULL;
    Option option;

    push_option(&stack, "A", "First");
    push_option(&stack, "B", "Second");
    push_option(&stack, "C", "Third");
    push_option(&stack, "D", "Fourth");
    while(stack != NULL) {
        option = pop_option(&stack);
        printf("Got option ... %s = %s\n", option.key, option.value);
        free_option(option);
    }
}