/home/lordaro/dev/openttd/src/core/smallstack_type.hpp:221:27: warning: instantiation of

      variable 'SmallStack<unsigned short, unsigned short, 65535, 8, 65533>::_pool' required

      here, but no definition is available [-Wundefined-var-template]

                        ThreadMutexLocker lock(_pool.GetMutex());

                                               ^

/home/lordaro/dev/openttd/src/cargopacket.h:502:32: note: in instantiation of member function

      'SmallStack<unsigned short, unsigned short, 65535, 8, 65533>::Pop' requested here

                        if (this->packets.find(next.Pop()) != this->packets.end()) return true;

                                                    ^

/home/lordaro/dev/openttd/src/core/smallstack_type.hpp:272:24: note: forward declaration of

      template entity is here

        static SmallStackPool _pool;

                              ^

/home/lordaro/dev/openttd/src/core/smallstack_type.hpp:221:27: note: add an explicit

      instantiation declaration to suppress this warning if 'SmallStack<unsigned short,

      unsigned short, 65535, 8, 65533>::_pool' is explicitly instantiated in another

      translation unit

                        ThreadMutexLocker lock(_pool.GetMutex());

                                               ^

1 warning generated.