From: Jason Green <news AT jgreen4 DOT fsnet DOT co DOT uk>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: template problem in djgpp
Date: Sun, 10 Jun 2001 23:41:39 +0100
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"Tomas Nilsson" <tnidt97 AT student DOT vxu DOT se> wrote:

> Hello,
> I have a problem with templates i djgpp 2.03. I have tried the following
> program:

Put the class declaration *and* implementation in the header:

> file class1.h:
> template<class TYPE>
> class class1 {
> private:
>         TYPE T;
> public:
>         void f1();
> };

> template <class TYPE> void class1<TYPE>::f1() {}
> 
> file main.cpp
> #include"class1.h"
> int main() {
>         class1<int> c1;
>         c1.f1();
> }
> 
> The program compiles without errors and warnings, but then something goes
> wrong in the
> linking process. The linker ld in djgpp returns the error message "undefined
> reference to class<int>::f1(void)". This is very strange, because the UNIX
> compiler CC can compile and build this program without any problem, and CC
> one of the best approximation of the C++ standard I know.
>     Can anyone see what could be causing this problem

gcc needs to see the class definition at compile time, otherwise
class1<int> does not exist at link time.

> and why it works in CC and not djgpp?

gcc DTRT here, so strictly speaking the other CC is buggy.