Linker Errors

[MiniDisc_2k2]

I have a class:

template <class T>
class linkedlist
{
protected:
class node
{
public:
T data;
node* next;
node* prev;
node() {next = NULL; prev = NULL;};
~node();
} *first;
public:
~linkedlist() { if (first!=NULL) delete first;};
void AddElement(cons t T &data);
T AddElement(istr eam &input);
void Append(const linkedlist* const data);
linkedlist() {first = NULL;};
};

template <class T>
linkedlist<T>:: node::~node()
{
if (next!=NULL)
delete next;

if (prev!=NULL)
prev->next = NULL;
}


That code is in linkedlist.h (some code was taken out). Please note that I
have defined NULL (if undefined) to be 0.

In main.cpp:

#include <iostream>
#include "linkedlist .h"

using namespace std;
int main(int argc, char* argv[])
{
...some code...

linkedlist<int> intlist;

.... some more code...

return 0;
}


When I compile this code, I get a linker error:

Linking...
main.obj : error LNK2001: unresolved external symbol "public: __thiscall
linkedlist<int> ::node::~node(v oid)" (??1node@?$link edlist@H@@QAE@X Z)
Debug/main.exe : fatal error LNK1120: 1 unresolved externals
Error executing link.exe.

Of course, I know what this means. It's saying that I never defined the
destructor to node. I thought I did. What am I doing wrong?

--
MiniDisc_2k2
To reply, replace nospam.com with cox dot net.

[John Harrison]

Re: Linker Errors


"MiniDisc_2 k2" <MattDelB@nospa m.com> wrote in message
news:h6pNa.4070 $ZT5.272@news2. east.cox.net...[color=blue]
> I have a class:
>
> template <class T>
> class linkedlist
> {
> protected:
> class node
> {
> public:
> T data;
> node* next;
> node* prev;
> node() {next = NULL; prev = NULL;};
> ~node();
> } *first;
> public:
> ~linkedlist() { if (first!=NULL) delete first;};
> void AddElement(cons t T &data);
> T AddElement(istr eam &input);
> void Append(const linkedlist* const data);
> linkedlist() {first = NULL;};
> };
>
> template <class T>
> linkedlist<T>:: node::~node()
> {
> if (next!=NULL)
> delete next;
>
> if (prev!=NULL)
> prev->next = NULL;
> }
>
>
> That code is in linkedlist.h (some code was taken out). Please note that I
> have defined NULL (if undefined) to be 0.
>
> In main.cpp:
>
> #include <iostream>
> #include "linkedlist .h"
>
> using namespace std;
> int main(int argc, char* argv[])
> {
> ...some code...
>
> linkedlist<int> intlist;
>
> ... some more code...
>
> return 0;
> }
>
>
> When I compile this code, I get a linker error:
>
> Linking...
> main.obj : error LNK2001: unresolved external symbol "public: __thiscall
> linkedlist<int> ::node::~node(v oid)" (??1node@?$link edlist@H@@QAE@X Z)
> Debug/main.exe : fatal error LNK1120: 1 unresolved externals
> Error executing link.exe.
>
> Of course, I know what this means. It's saying that I never defined the
> destructor to node. I thought I did. What am I doing wrong?
>[/color]

VC++ .NET gives

'member functions of nested classes of a template class cannot be defined
outside the class'

which I think is good advice although not standard C++.

g++ 3.2 compiles it fine.

I'd move the definition back inside the class.

john

[MiniDisc_2k2]

Re: Linker Errors

> VC++ .NET gives[color=blue]
>
> 'member functions of nested classes of a template class cannot be defined
> outside the class'
>
> which I think is good advice although not standard C++.
>
> g++ 3.2 compiles it fine.
>
> I'd move the definition back inside the class.
>
> john
>
>[/color]

thanks, yeah that fixed it. Shouldn't have though....