[Pkg-xmpp-devel] Bug#542512: dicod works with libgsasl7 1.1-1

[Simon Josefsson]

Looking at this more closely, this do not appear as problematic as first
can be thought.  The patch I proposed earlier solves a problem on mixed
stable/testing systems (such as for the original bug reported).  There
is no need to bump the shared library version of libgsasl7, which
Cascardo and I have discussed on the XMPP mailing list.

Here is what I'm trying.  Create gsasl.c:

#include <gsasl.h>
#include <stdio.h>
int main (void)
{
  printf ("header %s library %s\n", GSASL_VERSION,
	  gsasl_check_version (NULL));
  return 0;
}

Install libgsasl from stable:

apt-get install libgsasl7/stable libgsasl7-dev/stable

Build the tool:

jas at mocca:~$ gcc -o gsasl gsasl.c -lgsasl 

Invoke it:

jas at mocca:~$ ./gsasl
header 0.2.26 library 0.2.26
jas at mocca:~$ 

Now install libgsasl from testing, which has versioned symbols:

apt-get install libgsasl7/testing libgsasl7-dev/testing

Do NOT rebuild the application, just invoke it again:

jas at mocca:~$ ./gsasl
header 0.2.26 library 1.4.0
jas at mocca:~$ 

This works fine, and indicates that 1.4.0 is backwards compatible with
0.2.26 (at least for this simple test function).

Now rebuild the application using 1.4.0:

jas at mocca:~$ gcc -o gsasl gsasl.c -lgsasl 

Invoke it:

jas at mocca:~$ ./gsasl
header 1.4.0 library 1.4.0
jas at mocca:~$ 

That's expected.  Now install the old libgsasl, without symbol
versioning:

apt-get install libgsasl7/stable libgsasl7-dev/stable

Then invoke the tool again:

jas at mocca:~$ ./gsasl
./gsasl: /usr/lib/libgsasl.so.7: no version information available (required by ./gsasl)
header 1.4.0 library 0.2.26
jas at mocca:~$ 

This is the same warning message that the original reporter got.
However, note that the tool appears to work.

Thus it seems that if you build a tool (i.e., dicod or my example above)
using a modern version of libgsasl7 and then run the tool with an older
version of libgsasl7, the tool will still work fine but you will get a
linker warning.  In other words, the ABI of libgsasl7 is both forwards
and backwards compatible.

The reason for the warning, though, is not in libgsasl7 -- it is that
the tool was built incorrectly if the intention is that the tool should
work without warning on both old and new libraries.  However, I don't
think debian makes any guarantee that this should work.  If you upgrade
a tool to the version in unstable or testing on a stable system, you may
need to pull in whatever dependencies it has too, and essentially "you
are on your own".  It would be nice if these dependencies were
automatically installed, though, and my patches takes care of that (but
dicod needs to be rebuilt against a newer libgsasl7 for it to work).

Going back to dicod, here is what I get if I install dicod (2.0-7) with
libgsasl from stable:

mocca:/home/jas# ps auxww|grep dico
root     20050  0.0  0.0   4808   800 pts/4    S+   09:44   0:00 grep dico
mocca:/home/jas# /etc/init.d/dicod start
Starting dictionary server : dicod/usr/bin/dicod: /usr/lib/libgsasl.so.7: no version information available (required by /usr/bin/dicod)
 failed!
mocca:/home/jas# ps auxww|grep dico
dicod    20068  0.0  0.0   6792   596 ?        Ss   09:44   0:00 /usr/bin/dicod
root     20079  0.0  0.0   4808   796 pts/4    S+   09:44   0:00 grep dico
mocca:/home/jas# 

Note that dicod is running!  Launching it from a terminal works too:

mocca:/home/jas# ps auxww|grep dico
root     20212  0.0  0.0   4808   800 pts/4    S+   09:45   0:00 grep dico
mocca:/home/jas# /usr/bin/dicod
/usr/bin/dicod: /usr/lib/libgsasl.so.7: no version information available (required by /usr/bin/dicod)
mocca:/home/jas# echo $?
0
mocca:/home/jas# ps auxww|grep dico
dicod    20217  0.0  0.0   6792   592 ?        Ss   09:45   0:00 /usr/bin/dicod
root     20222  0.0  0.0   4808   800 pts/4    S+   09:45   0:00 grep dico
mocca:/home/jas# 

This indicates that the problem is just in the dicod init.d script,
which says 'fail' when the daemon outputs something on stdout/stderr.
It doesn't notice that dicod was started successfully anyway.

In other words, there is only a wishlist-kind of bug here.  The problem
is that the dicod init.d script says 'fail' where it should have said
'success', but the only situation where this happens if the user runs a
mixed testing/stable system and install dicod using libgsasl7 from
stable -- and that is not something that is supported.

The patch I proposed does not hurt, though, and if libgsasl7 had that
patch when dicod was built in testing, the user here could not have
installed dicod without also automatically pulling in libgsasl7.
However this is still only happening on mixed stable/testing systems,
which, again, I believe is not something that is generally supported.

/Simon