Bug#1026055: lapack breaks openturns autopkgtest: undefined reference to `ztrsyl3_' (and 3 more)

[Sébastien Villemot]

Hi Paul,

Le jeudi 15 décembre 2022 à 21:16 +0100, Paul Gevers a écrit :
> On 13-12-2022 21:59, Sébastien Villemot wrote:
> > The problem is that atlas needs to be recompiled against lapack 3.11.0.
> > Which has been done in atlas 3.10.3-13. But atlas itself cannot migrate
> > to testing because of #1025699.
> 
> While I understand recompiling "solves" the issue, normally this error 
> "undefined reference" hints at removal of symbols. Normally that should 
> be handled by a SONAME bump which would trigger auto trackers to be 
> generated for the transition. Such trackers notify the release team of 
> transitions and they can trigger rebuilds (you know that drill, 
> including the transition bug filing for coordination). Why do you think 
> that a SONAME bump wasn't the right solution in this case?

Actually the error is not due to a symbol removed, but to a symbol
*added*. So no SONAME bump is warranted.

Let me explain:

In lapack 3.11.0, several new symbols ({z,c,d,s}trsyl3_) were added to
liblapack.so.3 (a linear algebra library with a Fortran interface).
As a consequence, new wrapper functions around these symbols were also
added to liblapacke.so.3 (note the “e”), which is a C wrapper around
liblapack.so.3, and which is also shipped by src:lapack. Hence the
latest liblapacke.so.3 depends on the new symbols in liblapack.so.3.

Now, libatlas3-base (compiled from src:atlas) also provides its own
version of liblapack.so.3 (through the alternatives system¹). But,
until it is recompiled against lapack 3.11.0, that version of
liblapack.so.3 does not contain the new symbols. Hence, when
liblapack.so.3 is provided by libatlas3-base, loading liblapacke.so.3
produces the error that is seen in the failing test.

Essentially, what is missing is a restriction which would forbid the
co-installation of liblapacke ⩾ 3.11 and libatlas3-base compiled
against lapack < 3.11. I don’t know how to express that using our
tooling, but maybe I’m unimaginative.

I hope this clarifies.

Best,

¹ See https://wiki.debian.org/DebianScience/LinearAlgebraLibraries

-- 
⢀⣴⠾⠻⢶⣦⠀  Sébastien Villemot
⣾⠁⢠⠒⠀⣿⡁  Debian Developer
⢿⡄⠘⠷⠚⠋⠀  https://sebastien.villemot.name
⠈⠳⣄⠀⠀⠀⠀  https://www.debian.org

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