[Debconf-devel] Bug#413509: database communication does not work

[Joey Hess]

Frank Küster wrote:
> # apt-get --reinstall install x11-common 2>&1 | tee reinstall.lg
> Reading package lists...
> Building dependency tree...
> 0 upgraded, 0 newly installed, 1 reinstalled, 0 to remove and 3 not upgraded.
> Need to get 0B/334kB of archives.
> After unpacking 0B of additional disk space will be used.
> Do you want to continue [Y/n]? 
> DESTROY created new reference to dead object ' Qt::SpacerItem', <> line 1 during global destruction.
> Preconfiguring packages ...
> Use of uninitialized value in join or string at /usr/share/perl5/Debconf/DbDriver/Stack.pm line 104, <GEN1> line 4.

I can reproduce this:

debconf (user): trying frontend Kde
debconf (frontend): QTF: initializing app
debconf (frontend): QTF: initializing wizard
debconf (frontend): QTF: setting size
debconf (frontend): QTF: setting title
debconf (frontend): QTF: initializing main widget
        (in cleanup) DESTROY created new reference to dead object ' Qt::Object' at /usr/lib/perl5/Qt.pm line 445, <> line 1 during global destruction.

This bug occurs because dpkg-preconfigure forks and the subprocess
exits, calling Qt's DESTROY hooks. Apparently Qt behaves badly if the
DESTROY hooks are called before it actually displays anything. I think
this is a bug in libqt-perl, but I've committed a workaround to svn.

debconf (developer): --> 30 question skipped
debconf (developer): <-- GO 
debconf (frontend): QTF: -- START ------------------
debconf (frontend): QTF: -- END --------------------
Use of uninitialized value in join or string at /usr/share/perl5/Debconf/DbDriver/Stack.pm line 104, <GEN1> line 4.
debconf (db configdb): trying to setfield(x11-common/xwrapper/allowed_users value ) ..

It seems that the uninitialised value here is occuring because an undef is
being passed in when the value of the never displayed question is set.
That in turn happens because the kde frontend, unlike other frontend, does
not "show" nontinteractive elements. I've fixed it in svn.

That bug may be why debconf seemed to hang. An undef value goes in, and
the result is that values like x11-common/xwrapper/nice_value are read
out as "". If the x11-common/xwrapper/nice_value/error question is not
displayed for some reason (despite being critical priority),
x11-common's config script will loop forever.

I don't know about all the other strangeness however. No segfaults or
weird shell stuff reproduced here so far.

-- 
see shy jo
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