/*

* Search this source code for a comment with XXX. You must

* implement this missing functionality. When you run the program

* input should look like any of the following:

* push hi

* push whoah

* pop

* print

* push tho

* print

*

* I will execute something like the following and check that valgrind

* reports no errors.

*

* In my shell:

* $ printf "push $RANDOM push $RANDOM push $RANDOM pop print " | valgrind --leak-check=full ./stack

*/

#include

#include

#include

#include

struct node {

char* value;

struct node* next;

};

struct stack {

struct node* root;

};

struct stack*

stack_create(void)

{

struct stack* r;

r = malloc(sizeof * r);

if (r == NULL)

return NULL;

r->root = NULL;

return r;

}

/*

* XXX: You must implement this function. It should remove

* the top item on the stack and free the memory of both

* the value and the node that was removed.

*/

void

stack_pop(struct stack* stack)

{

}

bool

stack_push(struct stack* stack, const char* value)

{

struct node* node;

node = malloc(sizeof * node);

if (node == NULL)

return false;

node->value = strndup(value, strlen(value) - 1);

node->next = stack->root;

stack->root = node;

return true;

}

void

stack_print(struct stack* stack)

{

struct node* cursor;

size_t i = 0;

for (cursor = stack->root; cursor != NULL; cursor = cursor->next)

printf("[%zu] = %s ", i++, cursor->value);

return;

}

void

stack_destroy(struct stack* stack)

{

struct node* cursor, * next;

for (cursor = stack->root; cursor != NULL; cursor = next) {

next = cursor->next;

free(cursor);

}

return;

}

int

main(void)

{

struct stack* stack;

stack = stack_create();

for (;;) {

char* token;

char* line = NULL;

size_t length = 0;

ssize_t r;

const size_t push_l = strlen("push ");

r = getline(&line, &length, stdin);

if (r == -1)

break;

if (strncmp(line, "push ", push_l) == 0) {

line += push_l;

if (stack_push(stack, line) == false)

fprintf(stderr, "Stack push failed. ");

}

else if (strcmp(line, "pop ") == 0) {

stack_pop(stack);

}

else if (strcmp(line, "print ") == 0) {

stack_print(stack);

}

else {

fprintf(stderr, "Unknown command: must be one of push, pop and print. ");

}

}

stack_print(stack);

stack_destroy(stack);

return 0;

}

Please fill in the Missing Functionality using the C Program!.

The missing part is the 1st part where it's calling the function "stack_pop"