Re: [Boost-users] iostreams library and zlib/bzip2 support

From: Robert Vinluan (rvinluan_at_[hidden])
Date: 2006-02-13 10:24:00

Leon Mergen wrote:
> 
> Huh ? I don't understand... forgive me for my ignorance, since I'm 
> probably missing your point, but I just, for example, #include 
> <boost/iostreams/stream.hpp> and it just works, without linking to any 
> special lib... what exactly are your needs that require linking against 
> a lib? Or is it that bzip2/zlib support needs linking with a boost 
> library ?
> 
> Regards,
> 
> Leon Mergen
> http://www.solatis.com/

Hi Leon,

Thanks for the response.  I read my message again and found that it 
wasn't very clear.

Anyway, I'm building the boost iostreams library with zlib support. 
When I build it as a static library on Windows (i.e. 
libboost_iostreams-*.lib), everything works fine.  I can include the 
iostreams headers in my code and link my project to the library without 
any problems.

However, when I build iostreams as a dynamic library and link my project 
to its import library (i.e. boost_iostreams-*.lib), I receive linker 
errors about unresolved symbols.  The unresolved symbols are symbols 
from the iostreams' zlib component.

I did a symbol listing and found that all the symbols declared in 
./boost/iostreams/filter/zlib.hpp were available in the static library, 
but not in the import library.  So it seems that the corresponding 
implementation file, ./libs/iostreams/src/zlib.cpp, is not being 
compiled into the dynamic library.

So I checked the docs and found a small paragraph stating that if I 
wanted to include zlib.hpp in my code, then I needed to add zlib.cpp to 
my project as well as define the preprocessor symbol BOOST_IOSTREAMS_NO_LIB.

Here's a link to the doc page:
        http://www.boost.org/libs/iostreams/doc/installation.html
It's the first paragraph under the "Building with an IDE or Makefile" 
section.

Anyway, I followed the doc page and added zlib.cpp to my project.  I 
recompiled and relinked to the dynamic library and everything worked.

The doc page appears to backup my finding that zlib.cpp isn't being 
compiled into the dynamic version of the iostreams library.  So my 
question is .... why?  Why is zlib.cpp compiled into the static version 
of the iostreams library, but not the dynamic version?

I would really like to link against a dynamic version of iostreams with 
zlib support without explicitly adding zlib.cpp to my project.  Has 
anyone been able to do this successfully?

Thanks,
Rob