unity-2d-places crashed with SIGSEGV in QMetaObject::metacall()

Manual retrace, with love

Confirmed by duplicate.

In case it's useful, my duplicate bug 792238 contains additional description of how the UI appears to behave both before and after the crash occurs (e.g., after the crash, clicking the home button ineffectually toggles it between the pressed and unpressed states, without any menu coming up).

Not full backtrace in "manual_retrace"

#56 0x08051c50 in DashAdaptor::qt_metacall(QMetaObject::Call, int, void**) ()
No symbol table info available.
#57 0x00a79788 in ?? () from /usr/lib/libQtDBus.so.4

Using the information about missing symbols furnished by Didier Roche's trace, I just installed all the relevant debug symbol packages and ran unity-2d-places from the Terminal. In this way, I created duplicate bug 793044, which contains a considerably more complete stack trace (for all threads), and also possibly relevant console messages.

For those of you who are only interested in looking at the stack trace:
https://bugs.launchpad.net/ubuntu/+source/unity-2d/+bug/793044/+attachment/2155414/+files/Stacktrace.txt
https://bugs.launchpad.net/ubuntu/+source/unity-2d/+bug/793044/+attachment/2155415/+files/ThreadStacktrace.txt

For more details, see bug 793044 itself.

@Cristian: there is generally no more point to install debug symbols if not relevant past frame 30/40, here is frame 56, hence not installing the symbols file from there.

@Eliah: thanks for the stacktrace, continuing debugging this issue, I rebuilt qt with gcc 4.5 in oneiric instead of 4.6, and the issue is fixed by that. Now, time to hunt what gcc 4.6 does wrong, which won't be a joy

took in touch with the Qt guys: http://bugreports.qt.nokia.com/browse/QTBUG-19736 (launchpad doesn't recognize the url as a bug tracker link)

please lets rebuild qt4-x11 using a tightened b-d on g++-4.6 (>= 4.6.0-11ubuntu2) first, then scan for warnings like the ones that the upstream report points to.

so, just some catchup in this bug:
- tried with a newer gcc 4.6, still segfaulting
- tried with a -f-no-omit-frame-pointer, still segfaulting

wigglytext.qml example from qt4-demos segfault as well with Qt compiled with this version of gcc. See attached backtrace.

This bug was fixed in the package qt4-x11 - 4:4.7.3-1ubuntu2

---------------
qt4-x11 (4:4.7.3-1ubuntu2) oneiric; urgency=low

  [ Chase Douglas ]
  * Fix touch end event handling, LP: #785433
    - Updated kubuntu_28_xi2.1.patch with the fix

  [ Didier Roche ]
  * debian/rules:
    - use -fno-strict-aliasing for now as a lot of QML codes broke because of
      aliasing wrongly optimized. Issue under work upstream. (LP: #791213)
 -- Didier Roche <email address hidden> Wed, 08 Jun 2011 17:20:48 +0200

Added libqt-declarative in Arch Linux, as it was confirmed there by Andrea Scarpino (http://bugreports.qt.nokia.com/browse/QTBUG-19736?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=156025#comment-156025). Added Qt (also without a link, since Launchpad doesn't integrate with JIRA) while I was at it. I hope these additions are considered correct; if not, marking them Invalid won't hurt my feelings. ;-)

@Eliah: no worry, it's correct. Just think to close the Qt upstream bug report once fixed upstream manually please :)

@Didier Roche: Will do.

Marking Invalid in libqt-declarative in Arch Linux, since Andrea Scarpino has deleted the comment on the upstream Qt bug tracker that had confirmed it for Arch Linux (and searching https://bugs.archlinux.org doesn't reveal a report separately confirming it).