rem: if (! strcmp(continent1, continent2)) { return strcmp(country1, country2); } else { return strcmp(continent1, continent2); }
add: return strcmp(country1, country2);
context: gint sort_tree (GtkTreeModel *model,		GtkTreeIter *a,		GtkTreeIter *b,		gpointer user_data){    GValue value1 = {0, };    GValue value2 = {0, };    GValue value3 = {0, };    GValue value4 = {0, };    gchar * continent1, * continent2, * country1, * country2;    gtk_tree_model_get_value (model, a, CONTINENT_NAME_COLUMN, &value1);    gtk_tree_model_get_value (model, b, CONTINENT_NAME_COLUMN, &value2);    continent1 = (gchar *) g_value_get_string(&value1);    continent2 = (gchar *) g_value_get_string(&value2);    gtk_tree_model_get_value (model, a, COUNTRY_NAME_COLUMN, &value3);    gtk_tree_model_get_value (model, b, COUNTRY_NAME_COLUMN, &value4);    country1 = (gchar *) g_value_get_string(&value3);    country2 = (gchar *) g_value_get_string(&value4);    if (! strcmp(continent1, continent2))    {	return strcmp(country1, country2);    }    else    {	return strcmp(continent1, continent2);    }}