Bug#971812: gegl: version in buster not compatible with libc6 from bullseye

[Simon McVittie]

Control: reassign -1 libgegl-0.4-0 0.4.12-2
Control: retitle -1 gegl: version in buster not compatible with libc6 from bullseye
Control: severity -1 normal
Control: affects -1 + gimp

On Wed, 07 Oct 2020 at 20:47:59 +0200, Artur Linhart wrote:
> In the curent state of available packages from stable (buster) the program GIMP
> cannot be used.

*On a purely stable system*, it works fine. However, like the reporter
of #968342, you are using a system that mixes packages from stable
and testing:

> ii  libc6                2.31-3

The error message seen in the GUI is misleading, because it's guessing
that the reason the seamless-clone.so module didn't load successfully
is because gegl is too old (which it is not).

The warning shown when you run it from a terminal is more accurate:

> "$ gimp
> GEGL-Message: 20:38:16.980: Fehler beim Laden von Modul »/usr/lib/x86_64-linux-
> gnu/gegl-0.4/seamless-clone.so«: /usr/lib/x86_64-linux-gnu/libgegl-sc-0.4.so:
> undefined symbol: __exp_finite

This is because you are using the version of libc6 from testing (bullseye)
on a mostly-buster system, and the version of libgegl in buster has
assumptions that mean it works fine in buster, but breaks when libc6
is upgraded. Mixing packages from stable and testing is not something
that anyone can guarantee will work flawlessly.

This is not going to be something that can change in buster, unless the
release team would accept a stable-update that changes how libgegl is
linked in order to future-proof it against people upgrading core system
libraries to versions 18 months newer. I'm not sure they're going to go
for that, but I'll ask...

> This bug has been already reported as a bug https://bugs.debian.org/cgi-
> bin/bugreport.cgi?bug=968342 and was closed with the statement the dependency
> has to be used on libgegl-0.4-0 where the problem has been fixed, but the
> problem is, such version is not available on stable - buster, or even buster-
> backports.

Neither are libc6 version 2.31-3 and libgcc-s1 version 10.2.0-9, but
you seem to have installed those somehow.

    smcv