A linked list implemented in c

linked_list.c

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

typedef struct Node_t
{
	int data;
	struct Node_t* next;
}node_t;

typedef struct List_t
{
	node_t* head;
	node_t* tail;
}list_t;

void list_init(list_t*);
void list_print(list_t*);
void list_free(list_t*);
void list_populate(list_t*);
void list_insert(list_t*,int);
int list_remove(list_t*);
int list_empty(list_t*);

int main (void)
{
	list_t list;
	list_init (&list);
	printf( list_empty(&list) ? "Empty\n" : "Not Empty\n");
	list_populate (&list);
	int i;
	for (i = 0; i < 6; ++i)
	{
		printf("Element removed: %d\n", list_remove(&list));
		printf( list_empty(&list) ? "Empty\n" : "Not Empty\n");
	}
	list_populate (&list);
	printf("Element removed: %d\n", list_remove(&list));
	printf( list_empty(&list) ? "Empty\n" : "Not Empty\n");
	list_print (&list);
	list_free (&list);

	return 0;
}

int list_empty(list_t* list)
{
	return list->head == NULL;
}


int list_remove (list_t* list)
{
	node_t* temp;
	int data;

	assert (list != NULL);

	if (list->head == NULL)
	{
		fprintf(stderr, "Trying to remove a node_t from an empty list!\n");
		return -1;
	}

	temp = list->head;
	list->head = list->head->next;
	data = temp->data;
	free (temp);

	return data;
}

void list_insert (list_t* list, int data)
{
	node_t* newNode;
	char errStr [44];

	assert (list != NULL);

	newNode = (node_t*) malloc (sizeof(node_t));

	if (newNode == NULL)
	{
		sprintf (errStr, "malloc failure in list_insert(list*,%d):", data);
		perror(errStr);
		exit (0);
	}

	newNode->data = data;
	newNode->next = NULL;

	if (list->head == NULL)
	{
		list->head = newNode;
		list->tail = newNode;
	}
	else
	{
		list->tail->next = newNode;
		list->tail = newNode;
	}

	return ;
}

void list_populate (list_t* list)
{
	assert (list != NULL);
	printf("Populating List\n");
	list_insert(list,4);
	list_insert(list,3);
	list_insert(list,2);
	list_insert(list,1);
	list_insert(list,0);

	return ;
}

void list_init (list_t* list)
{
	list->head = NULL;
	list->tail = NULL;

	return ;
}

void list_print (list_t* list)
{
	node_t* next;
	assert (list != NULL);
	next = list->head;

	while (next != NULL)
	{
		printf("%d\n", next->data);
		next = next->next;
	}

	return ;
}

void list_free (list_t* list)
{
	node_t* next;

	assert (list != NULL);
	next = list->head;

	while (next != NULL)
	{
		list->head = list->head->next;
		free (next);
		next = list->head;
	}

	return ;
}