I'm implementing a hash table and linked list in C++ (no STL - don't ask) using templates, and I'm running into problems linking them with g++. If I #include all my .cpp files together, everything works, so my code definitely works, it's just the linking that's tripping me up.
I read the bit in the GCC manual about template instantiation, but wasn't sure how to apply it.
My problem:
I have a HashMap<T> and HashEntry<T> for my hash table (<T> is the value - my keys are std::strings). My linked list has LinkedList<T> and Node<T> (where <T> is the value).
In my hash map, I have:
template <class T> class HashMap {
...
private:
LinkedList< HashEntry<T> >** buckets;
}
Which gives me a linked list of HashEntry<T>s.
In a separate file, I have my Linked List class declaration:
template <class T>
class Node {
...
private:
T data;
}
template <class T> class LinkedList {
...
private:
Node<T> * first;
}
Then, when I try to link everything (after compiling with g++ -c -frepo *.cpp), I get:
g++ -frepo -o app LinkedList.o HashMap.o
[...unrelated errors about not having a main method - they go away when I link that in]
HashMap.o: In function `HashMap<int>::~HashMap()':
HashMap.cpp:(.text._ZN7HashMapIiED1Ev[HashMap<int>::~HashMap()]+0x65): undefined reference to `LinkedList<HashEntry<int> >::~LinkedList()'
HashMap.o: In function `HashMap<int>::insert(std::basic_string<char, std::char_traits<char>, std::allocator<char> >, int)':
HashMap.cpp:(.text._ZN7HashMapIiE6insertESsi[HashMap<int>::insert(std::basic_string<char, std::char_traits<char>, std::allocator<char> >, int)]+0xff): undefined reference to `Node<HashEntry<int> >::setData(HashEntry<int>)'
Googling around, I've seen suggestions for declaring the explicit template types that my program uses. This works for the HashMap and HashEntry (I added (template class HashMap< int > and template class HashEntry< int >.
However, I can't figure out how to make this work for LinkedList and Node classes, since the template instances are of HashEntries<int>. BUT, I can't put that into the LinkedList.h file, since it's #included by my Hash tables. I also couldn't get an advanced/extern declaration working for it.
I'm sure there's something fairly simple that I'm missing to make all this work. Any tips?
