RE: [boost] shared_ptr hierarchy question

From: Schaible, Joerg (Joerg.Schaible_at_[hidden])
Date: 2000-10-20 06:57:16

Hi Csaba,

> Would not the example still hold without any reference to 
> shared_ptr?? (see
> code below)
The code was not meaningful in any way, it was just to demonstrate the
situation.

> Conclusion is not to export classes with template members - 
> yes, I'd expect
> this behavior given the limits of DLLs anyway.
This is a compiler issue. Basically it should *not* matter, whether I put my
library into a DLL (or shared lib) or not. For DLL's this is challenge for
the compiler vendor, but not unresolvable.

> I would never 
> try to export
> *any* templates from a DLL:
> 
> 1) the MSVC compiler seems to require to see all the template 
> code when it
> needs to instantiate one
> 2) the MSVC compiler requires that "exported" template code 
> go to headers
> (exporting of template stuff is not supported)
This is no real limitation caused by building a DLL. IMHO there are not very
much compilers around that support templates without seeing their full
implementation. If a compiler support "extern template" it is not far away
form supporting exports from a DLL, too.

> Also, DLLs are limited in a number of other ways (i.e., 
> memory allocation
> should consistently happen within the DLL xor the client).
Sorry. This is not true. You should just allocate/free the memory from the
same manager independent where the code lives. But this is true for all kind
of memory management in applications and libraries.

> Best to think of Win32 DLLs as being invented for C.
I've build C++-DLL's and shared libraries for Windows, OS/2 and Unix
flavours for more than 8 years. I've never detected that ANSI-C describes
any library technology.

Greetings,
Jörg