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?

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MiniDisc_2k2
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[John Harrison]

"MiniDisc_2 k2" <Ma******@nospa m.com> wrote in message
news:h6******** ********@news2. east.cox.net...

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?

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]

> 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

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