Crash in csladspa when starting ardour

[Jean-Marie Aubry]

Using Ubuntu 17.10, csladspa 1:6.09.1~dfsg-2 and ardour 5.12.

On starting ardour:

Thread 1 (Thread 0x7ffff7f8b8c0 (LWP 9037)):
#0 __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:51
#1 0x00007fffed074f5d in __GI_abort () at abort.c:90
#2 0x00007fffed0bd28d in __libc_message (action=action@entry=do_abort,
    fmt=fmt@entry=0x7fffed1e4528 "*** Error in `%s': %s: 0x%s ***\n")
    at ../sysdeps/posix/libc_fatal.c:181
#3 0x00007fffed0c464a in malloc_printerr (action=<optimised out>,
    str=0x7fffed1e0eae "free(): invalid pointer", ptr=<optimised out>,
    ar_ptr=<optimised out>) at malloc.c:5426
#4 0x00007fffed0c673e in _int_free (av=0x7fffed416c20 <main_arena>,
    p=<optimised out>, have_lock=0) at malloc.c:4175
#5 0x00007fffed0cb44e in __GI___libc_free (mem=<optimised out>)
    at malloc.c:3145
#6 0x00007fffc51bf400 in ?? () from /usr/lib/ladspa/csladspa.so
#7 0x00007fffc51bf622 in ladspa_descriptor () from /usr/lib/ladspa/csladspa.so
#8 0x00007ffff70ef39b in ARDOUR::PluginManager::ladspa_discover(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >) ()
   from /opt/Ardour-5.12.0/lib/libardour.so.3
#9 0x00007ffff70f02d7 in ARDOUR::PluginManager::ladspa_refresh() ()
   from /opt/Ardour-5.12.0/lib/libardour.so.3
#10 0x00007ffff70f0a52 in ARDOUR::PluginManager::refresh(bool) ()
   from /opt/Ardour-5.12.0/lib/libardour.so.3

The only workaround for now is to uninstall csladspa.

Related ardour bug report: http://tracker.ardour.org/view.php?id=7502

[Erich Eickmeyer (eeickmeyer)]

Fixed in upstream Debian, needs SRU.

[Erich Eickmeyer (eeickmeyer)]

[Impact]

 * Currently, this is the number one bug affecting Ardour users of Ubuntu (including Ubuntu Studio).
 * Please see https://discourse.ardour.org/t/ubuntu-studio-17-10-problem/88933 , https://discourse.ardour.org/t/process-error-ardour-wont-launch/99829 , https://discourse.ardour.org/t/ardour-wont-load-existing-sessions-or-new-sessions-paid-user/99895

[Test Case]

 * Install Ardour in Ubuntu (or simply installing Ubuntu Studio) and run Ardour. Large potential for immediate crash without explanation or apport bug.

 * Workaround: uninstall csladspa

[Regression Potential]

 * None.

[Other Info]

 * Per the Ardour team, this is currently their number one bug report. Only workaround is to remove csladspa which isn't ideal for Ubuntu Studio users expecting the distro to work "out of the box."
 * Working with the Ardour team keeps (and/or reestablishes) Ubuntu (and therefore Ubuntu Studio) as a recommended distro for audio production and use of their product. This bug is currently an hindrance to that effort.

[Colin Watson (cjwatson)]

It looks like the upstream fix was just a matter of deleting one line. We should try cherry-picking just that change first. It was part of a commit with some other changes upstream, but here's a link to the relevant part of the patch:

  https://github.com/csound/csound/commit/7bad3e3801e219860d91b1845f42c87812fc1d89#diff-8839482122d7aa14591d57f3e35f47cc

[Colin Watson (cjwatson)]

We shouldn't close bugs without explaining why. So here's the explanation: the original bug report here was fixed in an upstream commit that was part of csound 6.10.0, which is in Ubuntu 18.04. (Ubuntu 17.10 is end of life, so the supported way to get this fix is to upgrade to 18.04.)

Now, there appears to be a *separate* bug in the csladspa code in csound which is reportedly not fixed in 18.04, and that's what Erich's comments above relate to. We'll track that as a separate bug report.