assertions when stopping unityshell plugin: g_hash_table_remove_internal: assertion `hash_table != NULL' failed

[Adam Dingle]

Every time the unityshell plugin is unloaded from compiz, this critical assertion is printed many times:

(compiz:11468): GLib-CRITICAL **: g_hash_table_remove_internal: assertion `hash_table != NULL' failed

To see this, use CompizConfig Settings Manager to enable a new plugin such as the JPEG image loader. That will cause all existing plugins to be reloaded, and the assertion above will appear many times in .xsession-errors.

The assertion might be benign, but we should still find and fix it.

[Adam Dingle (adam-yorba)]

By the way, I'm running compiz 1:0.9.9~daily13.04.10-0ubuntu1 and unity 7.0.0daily13.04.10-0ubuntu1 on Ubuntu Raring. Here's a stack trace for the assertion:

#0 g_logv (log_domain=0x7ffff5bc994e "GLib", log_level=G_LOG_LEVEL_CRITICAL, format=<optimized out>, args=args@entry=0x7fffffffde08)
    at /build/buildd/glib2.0-2.36.0/./glib/gmessages.c:981
#1 0x00007ffff5b8e492 in g_log (log_domain=log_domain@entry=0x7ffff5bc994e "GLib", log_level=log_level@entry=G_LOG_LEVEL_CRITICAL,
    format=format@entry=0x7ffff5bd338a "%s: assertion `%s' failed") at /build/buildd/glib2.0-2.36.0/./glib/gmessages.c:1010
#2 0x00007ffff5b8e4b9 in g_return_if_fail_warning (log_domain=log_domain@entry=0x7ffff5bc994e "GLib",
    pretty_function=pretty_function@entry=0x7ffff5bce5c0 <__PRETTY_FUNCTION__.4671> "g_hash_table_remove_internal",
    expression=expression@entry=0x7ffff5bce304 "hash_table != NULL") at /build/buildd/glib2.0-2.36.0/./glib/gmessages.c:1019
#3 0x00007ffff5b760ad in g_hash_table_remove_internal (hash_table=<optimized out>, key=<optimized out>, notify=<optimized out>)
    at /build/buildd/glib2.0-2.36.0/./glib/ghash.c:1269
#4 g_hash_table_remove_internal (hash_table=0x0, key=0x136d310, notify=1) at /build/buildd/glib2.0-2.36.0/./glib/ghash.c:1262
#5 0x00007fffe6d3e12f in nux::Object::Destroy() () from /usr/lib/x86_64-linux-gnu/libnux-core-4.0.so.0
#6 0x00007fffe6d3e3d2 in nux::Object::UnReference() () from /usr/lib/x86_64-linux-gnu/libnux-core-4.0.so.0
#7 0x00007fffe2c22a7a in unity::panel::Controller::~Controller() () from /usr/lib/compiz/libunityshell.so
#8 0x00007fffe2b2902a in unity::UnityScreen::~UnityScreen() () from /usr/lib/compiz/libunityshell.so
#9 0x00007fffe2b29449 in unity::UnityScreen::~UnityScreen() () from /usr/lib/compiz/libunityshell.so
#10 0x00007ffff7ba0658 in CompManager::finiPlugin(CompPlugin*) () from /usr/lib/libcompiz_core.so.ABI-20130125
#11 0x00007ffff7ba1db1 in CompPlugin::pop() () from /usr/lib/libcompiz_core.so.ABI-20130125
#12 0x00007ffff7b71e2f in compiz::private_screen::PluginManager::updatePlugins(CompScreen*, std::vector<CompOption::Value, std::allocator<CompOption::Value> > const&) ()
   from /usr/lib/libcompiz_core.so.ABI-20130125
#13 0x00007ffff7b735d2 in PrivateScreen::processEvents() () from /usr/lib/libcompiz_core.so.ABI-20130125
#14 0x00007ffff7ba70c7 in CompEventSource::callback() () from /usr/lib/libcompiz_core.so.ABI-20130125
#15 0x00007ffff608697f in Glib::Source::dispatch_vfunc(_GSource*, int (*)(void*), void*) () from /usr/lib/x86_64-linux-gnu/libglibmm-2.4.so.1
#16 0x00007ffff5b86f05 in g_main_dispatch (context=0x615f90) at /build/buildd/glib2.0-2.36.0/./glib/gmain.c:3054
#17 g_main_context_dispatch (context=context@entry=0x615f90) at /build/buildd/glib2.0-2.36.0/./glib/gmain.c:3630
#18 0x00007ffff5b87248 in g_main_context_iterate (context=0x615f90, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>)
    at /build/buildd/glib2.0-2.36.0/./glib/gmain.c:3701
#19 0x00007ffff5b876ba in g_main_loop_run (loop=0x615cb0) at /build/buildd/glib2.0-2.36.0/./glib/gmain.c:3895
#20 0x000000000040194b in main ()