template compile errors

From: Thomi Richards (thomi_at_thomi.imail.net.nz)
Date: 10/13/04 

Date: 12 Oct 2004 19:28:32 -0700

Hi,

I'm trying to create a simple stack class using C++ and templates.
Everything works well and good if I amke the class totally inline.
However, as soon as I try to seperate the class into a .h and a .cpp
file, gcc throws some strange linking errors.

Compiling like this:

gcc test.cpp stackList.cpp -lstdc++ -o test

produces these errors:

/tmp/ccCJLrbl.o(.text+0x84): In function `main':
: undefined reference to `Stack<int>::Stack[in-charge]()'
/tmp/ccCJLrbl.o(.text+0x101): In function `main':
: undefined reference to `Stack<int>::push(int)'
/tmp/ccCJLrbl.o(.text+0x10c): In function `main':
: undefined reference to `Stack<int>::size() const'
/tmp/ccCJLrbl.o(.text+0x18b): In function `main':
: undefined reference to `Stack<int>::empty() const'
/tmp/ccCJLrbl.o(.text+0x19c): In function `main':
: undefined reference to `Stack<int>::size() const'
/tmp/ccCJLrbl.o(.text+0x1aa): In function `main':
: undefined reference to `Stack<int>::pop()'
/tmp/ccCJLrbl.o(.text+0x20f): In function `main':
: undefined reference to `Stack<int>::~Stack [in-charge]()'
/tmp/ccCJLrbl.o(.text+0x229): In function `main':
: undefined reference to `Stack<int>::~Stack [in-charge]()'
collect2: ld returned 1 exit status

I'm tearing my hair out... why would it not work in seperate files? My
class definition is something like this:

template <class T>
class Stack
{
private:
    StackNode<T> *stackHead;
    /// The number of elements on the stack. It's easier to keep count
    /// of them here than to count them every time we need them.
    unsigned int stackSize;
protected:
public:
    /// Default constructor: set the stackSize to be 0.
    Stack(void);

    /// Default destructor: clean up any memory allocated.
    ~Stack(void);
    /// push: push an item onto the stack, and incrememt the size.
    bool push(T item);

    /// pop: return the topmost element from the stack, removing it
from the stack at the same time:
    T pop(void);

    /// size: returns how many items are on the stack:
    unsigned int size(void) const;
    /// empty: return true if the stack is empty:
    bool empty(void) const;
    /// full: return true if the stack is full: - for a linked list
implementation, this can be safely ignored:
    bool full(void) const;

};

and the code for a single method for the above class looks like this:

template <class T> bool Stack<T>::push(T item)
{
    if (full())
        return false;

    StackNode<T> *node = new StackNode<T> (item);
    node->Head = stackHead;
    stackHead = node;
    stackSize++;

    return true;
}

I've been following the C++ language tutorial, and a few books I own
at home. It looks like I'm doing everything properly... Can anyone
shed some light on this?

Thanks,

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