[prog] C++ strange linking behaviour

[Wolfgang Petzold]

Am 11/09/2004 12:04 AM schrieb Meredith L. Patterson:
> Wolfgang Petzold wrote:
>> That's for *template* classes only, right? If I include the
>> implementation of non-template class methods more than once I will
>> get a "multiple definition" error ...
> 
> This is what #ifndef wrappers are for. If you wrap your header file in 
> preprocessor directives like [...]

I was thinking of a rather constructed example (and then again, maybe
it's not that constructed at all):

foo.h: non-template foo class and its implementation
bar.cxx: some function that uses the foo class
main.cxx: main() function that uses the foo class and the function
          from bar.cxx

and then compile

bar.cxx  (includes foo.h) --> bar.o  \
                                      >--> main
main.cxx (includes foo.h) --> main.o /

In this case guards won't help.

Anyway, my originating question is solved: Template class
implementation code has to be available at compile time
to any code that uses the template class.

Regards
Wolfgang