Bug#620629: mathgl: NMU for these bugs

[Steve Langasek]

Hi Dimitrios,

On Sat, Jun 18, 2011 at 11:41:02AM +0300, Dimitrios Eftaxiopoulos wrote:

> Thank you for your patch regarding symbol failures of mathgl. In a recent
> communication with Sylvestre Ledru we decided to to drop symbol files due
> to many FTBFS and due to the much time consuming effort of editing the
> symbols files after each FTBFS.  This is what I was planning to do when I
> will build and upload the new version 1.11.2.  If you think that it is
> worth keeping the symbols files and we can avoid multiple FTBFS with your
> changes, I don't mind keeping them.

It is my opinion that every library package in the archive should use symbol
files eventually.  The two main benefits of symbol files are:

 - reverse-dependencies that only use older symbols will have a weaker
   versioned dependency on the library, making upgrades easier
 - accidental upstream library ABI changes won't go unnoticed in the
   package, being caught by the ABI checker (which is what's been giving
   problems here so far).

The build failures have been almost entirely due to symbols that are not
part of the library ABI, but are g++ implementation details instead.  These
symbols should be correctly marked 'optional', because /for each
architecture/, they will come and go with changes to the toolchain.  I think
the reason you were having so many problems nailing down the symbol files is
because you were racing various toolchain changes on the different
architectures. :)

My previous NMU did turn up a handful more symbols which also need to be
marked 'optional', as I said it might.  But after that, mathgl should build
on all architectures and the symbols files should be mostly stable.  There
is the possibility of future toolchain changes causing further changes to
which destructors are exported in the symbol table, but those can again be
handled by marking the destructor symbols optional.  (I haven't tried to do
this yet because there are a bunch of destructors for foreign classes whose
destructors are exported, and I don't completely understand why these are
exported on one architecture vs. another.  But it's *probably* safe for you
to mark all foreign destructors as optional.)

Anyway, attached are the NMU patches from a second NMU (both an incremental
patch versus the previous NMU, and a full diff for the two NMUs), which I
will upload shortly.  With this, mathgl will build on all official
architectures, and should also build on all the debian-ports architectures
(though I can't be certain of this, because no ports architecture has tried
to build the package since my previous upload).

If you are still considering dropping the symbols files, please file a bug
report against dpkg-dev first.  If it's at all possible to do so,
dpkg-gensymbols should be handling these kinds of optional symbols
centrally, not requiring maintainers to manually tag them all as optional.
I'd hate to see us lose symbols files from the archive because a maintainer
found them too difficult to use.

Thanks,
-- 
Steve Langasek                   Give me a lever long enough and a Free OS
Debian Developer                   to set it on, and I can move the world.
Ubuntu Developer                                    http://www.debian.org/
slangasek at ubuntu.com                                     vorlon at debian.org
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