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On 2011-12-27T13:51:31+00:00 Morten-hustveit wrote:

This simple test case from 2008 aborts on an assertion within 1 second
on every run:

  http://lists.freedesktop.org/archives/xcb/2008-November/004030.html

The test case will trigger any of two asserts, but one of them can be
eliminated by applying the patch found here:

  https://bugs.freedesktop.org/show_bug.cgi?id=29875

The assertion mentioned in this report's summary remains.

Reply at: https://bugs.launchpad.net/ubuntu/+source/qtdeclarative-
opensource-src/+bug/1179617/comments/0

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On 2011-12-28T04:37:03+00:00 Psychon-d wrote:

This assertion seems to be a bug in Xlib instead of xcb. I added the
following assert() to xcb_writev() (since xcb_take_socket() has to be
called before it may be used) and now this assert triggers instead of
the one from the summary.

 assert(c->out.return_socket != NULL);

Should I send this assert() as a git-formatted patch to the mailing list?
Should this bug be reassigned to Xlib?

Reply at: https://bugs.launchpad.net/ubuntu/+source/qtdeclarative-
opensource-src/+bug/1179617/comments/1

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On 2011-12-29T17:42:44+00:00 Josh Triplett wrote:

(In reply to comment #1)
> This assertion seems to be a bug in Xlib instead of xcb. I added the following
> assert() to xcb_writev() (since xcb_take_socket() has to be called before it
> may be used) and now this assert triggers instead of the one from the summary.
> 
>  assert(c->out.return_socket != NULL); 
> 
> Should I send this assert() as a git-formatted patch to the mailing list?
> Should this bug be reassigned to Xlib?

By all means reassign this bug to Xlib.  However, please don't add
assertions to XCB that trigger on programs using Xlib; we've learned
from previous assertions that people really don't like having their
programs throw assertion failures, and when the assertions come from XCB
they blame XCB rather than blaming Xlib or their programs.  Let's have
them correctly blame Xlib instead this time. :)

That said, thanks for your further diagnosis of the problem.  From what
you found, it definitely sounds like Xlib tried to call xcb_writev
without owning the socket, which should never happen.

Reply at: https://bugs.launchpad.net/ubuntu/+source/qtdeclarative-
opensource-src/+bug/1179617/comments/2

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On 2012-01-24T12:06:23+00:00 Psychon-d wrote:

ARGH.
Took me a while but I finally figured it out. The fix is simple:

Just call XInitThreads() before XOpenDisplay() and all the problems
disappear.

(Reassigning to libX11 and closing as INVALID)

Reply at: https://bugs.launchpad.net/ubuntu/+source/qtdeclarative-
opensource-src/+bug/1179617/comments/3

------------------------------------------------------------------------
On 2014-04-08T13:19:02+00:00 Ulf-hermann wrote:

I don't think just calling XInitThreads() fully resolves it as I still
get bugs like https://bugreports.qt-
project.org/browse/QTCREATORBUG-11960 and https://bugreports.qt-
project.org/browse/QTBUG-31935 even though Qt calls XInitThreads().

Reply at: https://bugs.launchpad.net/ubuntu/+source/qtdeclarative-
opensource-src/+bug/1179617/comments/11


** Changed in: qt
       Status: Unknown => Confirmed

** Changed in: qt
   Importance: Unknown => Medium

** Bug watch added: freedesktop.org Bugzilla #29875
   https://bugs.freedesktop.org/show_bug.cgi?id=29875

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https://bugs.launchpad.net/bugs/1179617

Title:
  qmlscene assert failure: qmlscene: ../../src/xcb_conn.c:180:
  write_vec: Assertion `!c->out.queue_len' failed.

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