RE: [Log4cpp-devel] Warning: win32 dll can't export containerclasses

[David R. <dre...@mo...>]

Yeah, it sucks pretty bad. I don't know if it is still true with the
latest version of MSVC (MSVC.NET? MSVC7?).=20

The problem also applies to Category::getAllAppenders().

I'm not sure that the problem is so significant. It is only relevant to
the win32 dll build: maybe the problem methods can be made private for
that build? Or just put warnings in the documentation?

Your solution to change the container returned to std::vector would be
nice though... At least with getAllAppenders() it wouldn't break any
production release APIs.

Regards,

David Resnick
MobileSpear Inc.
=20

-----Original Message-----
From: Bastiaan Bakker [mailto:Bas...@li...]=20
Sent: Tuesday, June 25, 2002 10:35
To: David Resnick
Cc: log...@li...
Subject: Re: [Log4cpp-devel] Warning: win32 dll can't export
containerclasses


Hmm, that sucks. Any chance of MS fixing this problem soon? Being
limited to only use std::vector in your APIs is ridiculous. However
currrently only getCurrentCategories() is affected. It uses std::set
now, but changing that to std::vector wouldn't hurt very much,=20
and may be more efficient as std::vector is the simplest container in
most STL implementations. Yes, it's an incompatible API change, but
0.3.x is a development branch anyway.=20

Regards,

Bastiaan

PS. The above is not a commitment to keep the log4cpp API MSVC DLL
export clean.

 =20
On Sun, 2002-06-23 at 10:08, David Resnick wrote:
> I found this out when trying to use Category::getCurrentCategories(),=20
> which returns std::set<Category*>*. The set I got had 1 good pointer;=20
> the rest were invalid.
>=20
> The problem is detailed by MS in Q168958 "HOWTO: Exporting STL=20
> Components Inside & Outside of a Class". Here is the key paragraph:
>=20
> "Some STL classes contain nested classes. These classes can not be=20
> exported. For instance, deque contains a nested class deque::iterator.

> If you export deque, you will get a warning that you must export=20
> deque::iterator. If you export deque::iterator, you get a warning that

> you must export deque. This is caused by a designed limitation that=20
> once a template class is instantiated, it can not be re-instantiated=20
> and exported. The only STL container that can currently be exported is

> vector. The other containers (that is, map, set, queue, list, deque)=20
> all contain nested classes and cannot be exported."
>=20
> So if you want to use methods such as=20
> Category::getCurrentCategories(), do them in a helper class that is=20
> linked as part of the DLL. I added what I needed to the=20
> SimpleConfigurator (what I needed to do was delete previously defined=20
> appenders from all categories before reloading a config file, so it=20
> made sense in any case to put it there.)
>=20
> Regards,
>=20
> David Resnick
> MobileSpear Inc.=20
>=20
>=20
>=20
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