Bug#1136641: debian-policy: do not require shared libraries to change package name with soname changes

On Thu, May 14, 2026 at 10:46:59AM +0200, Ansgar wrote:
> 2. Coinstallability should be mentioned as a concern for libraries
> with many reverse dependencies, but should explictly state that this
> requires the entire dependency chain to be coinstallable. Note that
> "Depends: libfoo-common (>= X)" runs into the risk that newer
> libfoo-common packages break older library versions and are safe only
> when extraordinary care is taken; the same is true for
> "libfoo-bin". (One could use libfooX-common, libfooX-bin packages
> where data and helper binaries are installed into paths that change
> with the SONAME such as /usr/lib/libfooX/libfoo-helper.)

During an upgrade even if the file libfoo.so.N is removed, programs
linked against libfoo.so.N might still be running and might still attempt to
access files in libfoo-common or libfoo-bin.
So the new libfoo-common/libfoo-bin still need to be compatible with the old
libfoo.so.N, 

Given the library packages only contain a library file, they cannot have file
conflicts with other packages so coinstability should not be an issue.

So policy should continue to require coinstability.

Cheers,