/tmp/ccGwF8Kw.o: In function `Stack<SubData>::push(SubData*)':
Stack.cpp:(.text._ZN5StackI7SubDataE4pushEPS0_[Stack<SubData>::push(SubData*)]+0x24): undefined reference to `List<SubData>::List(SubData*)'
/tmp/ccGwF8Kw.o: In function `Stack<SubData>::~Stack()':
Stack.cpp:(.text._ZN5StackI7SubDataED1Ev[Stack<SubData>::~Stack()]+0x1b): undefined reference to `List<SubData>::~List()'
collect2: ld returned 1 exit status