allocating mem using glib

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

typedef struct
{
    int item_id;
    unsigned char *item_name;
    double item_price;
    int item_stock_count;
} item_data;

void print_item(item_data *item_ptr)
{
    printf("item_id: %i,\n item_name: %s,\n item_price: %g,\n item_stock: %i\n",
        item_ptr->item_id,
        item_ptr->item_name,
        item_ptr->item_price,
        item_ptr->item_stock_count);
}

int main()
{
    GSList *items_list1 = NULL, *iterator = NULL;
    item_data *tmp_item = NULL;
    int i = 0;
    char *tmp_str = NULL, *tmp_str2 = NULL;

    tmp_str = malloc(1);

    for(i = 0; i < 3; i++)
    {
        sprintf(tmp_str, "%d", i);

        tmp_str2 = (unsigned char *)malloc(100);
        if (tmp_str2 == NULL)
        {
            fprintf(stderr, "Couldn't allocate memory\n");
            return -1;
        }

        strcpy(tmp_str2, "item_num num: ");
        strcat(tmp_str2, tmp_str);


        // ***Allocate memory using glib***
        tmp_item = g_new(item_data, 1);
        if (tmp_item == NULL)
        {
            fprintf(stderr, "Couldn't allocate memory\n");
            return -1;
        }

        tmp_item->item_id = i;
        tmp_item->item_name = tmp_str2;
        tmp_item->item_price = 100*(i+1);
        tmp_item->item_stock_count = 10*(i+1);

        items_list1 = g_slist_append(items_list1, tmp_item);
    }

    // Clean up
    for(iterator = items_list1; iterator != NULL; iterator=iterator->next)
    {
        free(((item_data*)iterator->data)->item_name);
        g_free(iterator->data);
    }

    for(iterator = items_list1; iterator != NULL; iterator=iterator->next)
        print_item((item_data*)iterator->data);

    return 0;
}