[prog] C++ strange linking behaviour

[Miriam Ruiz]

> 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 ... Yeah, I think
> I see. Thank you
> both, Miriam and Kathryn.

Yep, it's only for the template part. The non-template
implementation goes in the .cpp files as always.

Sometimes coders put the templated code in a different
header than the definitions to be a bit more
structurated.

> On a more general level, I'm still a bit confused,
> though. I always
> thought, header files are where declarations and
> prototypes go, and the
> actual implementations go into another file. It's
> not a matter for me
> now (and probably won't be in the near future), but
> if I were selling a
> C++ template library I would have to give out the
> implementation code,
> too (the "templated" parts of it), for the library
> to be able to be
> used. Is this right?

Yep, for what I know, that's true. The other trick
would be to force the compiler to build some of the
versions of the templated code for certain classes in
another file, so it was already compiled and thus
could be linked, but I guess it's a poor idea that
throws away all the power of templates.

Miry


	
	
		
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