Multiple so-versions of a lib in unstable are bad

[Adrian Bunk <bunk@fs.tum.de>]

Hi Chris,

while reading throuch debian-devel archives I read your "libraries being 
removed from the archive" mail.

There's at least one good reason why having several so-versions of a 
library in unstable is usually a bad idea:

Inter-library dependencies open a _big_ range of sometimes hard to debug 
problems if a binary is linked with two so-versions of a library.

An Example:

Package: proga
Depends: libt0, libd0

Package: libv0
Depands: libd0


If libd1 is uploaded and only one of proga and libv0 is recompiled with
libd1 this results in proga linked with both so-versions of the library. 
I remember problems with two so-versions of libpng, later with
libssl0.9.6 and libssl0.9.7, and with libvorbis (at the time of the big
libvorbis breakage [1] I backported the recent libvorbis package to
woody, which broke some KDE apps for people also using a KDE
backport [2,3]). If you remove the old so-version when the new
so-version enters unstable this forces all maintainers to recompile
their packages and therefore this problem is currently only rarely
observed. Unless you offer a good solution for this problem the main
effect of your proposal will be many breakages in programs linked with
two or more so-versions of a library at the same time.

There are problems with so-name changes (I remember one library having
5 (five) different so-names within one month), but they should be 
solvable via communication between maintainers.

cu
Adrian

BTW: Please Cc me on replies.

[1] #156227, #156365, #161961, #178756; a fix was uploaded seven months
    after the first RC bug was reported
[2] http://lists.debian.org/debian-kde/2003/debian-kde-200301/msg00430.html
[3] I'm inclined say, either the kdelibs or the libvorbis maintainer 
    shoult explain the exact cause of these crashes, but that would be a
    personal offense...

-- 

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       "Only a promise," Lao Er said.
                                       Pearl S. Buck - Dragon Seed