[Pkg-pascal-devel] Bug#820566: Bug#820566: view3dscene: please stop depending on libpng12-0

[Tobias Frost]

On Sun, 10 Apr 2016 14:04:19 +0200 Paul Gevers <elbrus at debian.org>
wrote:
> Hi Tobias,
> 
> Thanks for working on this and the NMU.
> 
> On 10-04-16 10:05, Tobias Frost wrote:
> > At ldd claims a dependency ... (I recompiled it against libpng16)
> >  
> > # ldd view3dscene | grep png
> >         libpng16.so.16 => /usr/lib/x86_64-linux-gnu/libpng16.so.16
> > (0x00007f67172e0000)
> > 
> > (To get forward with the transition I'll upload a NMU with an
updated
> > dependency, but I'll keep that bug open, because this issue is too
> > smelly.. For sure the current binary will have problems if the lib
is
> > indeed required. )
> 
> Can you elaborate a little bit more what you mean with the smelly
part
> and the last sentence? Do you mean that you think this should be
> automatically detected, or do you (also) mean something else?


It is simply strange that you have to specify "by hand" the .so your
binary needs, and it is error prone, as we are seeing now:
view3dscene has been (silently) recompiled against libpng16 and despite
the depends line it is not ensured that the right libpng will be pulled
in on install.

Could you generate the depends at buildtime, detect that and bail out
or  or use a build conflict to catch those cases? 

> From past communication with upstream I learned that the libpng and
zlib
> libraries are loaded dynamically (dlopen, dlsym). You can even run
> view3dscene without libpng/zlib installed, except you will not be
able
> to load gzip-compressed X3D files or read PNG textures. In usual
cases
> these 2 features are quite important, so we want to always depend on
> libpng and zlib.
> 
> @Michalis, does view3dscene work with libpng16, or do you first need
to
> port view3dscene to that API? If so, we better just drop the
dependency
> for now.
> 
> Paul
> 


-- 
tobi