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Linux: libxcb assertion failure causes program crash



  • My program uses multiple GL contexts (in their own threads) and a Quick context. It crashes predictably with a SIGABRT and the following message:

    ../../src/xcb_conn.c:186: write_vec: Assertion `!c->out.queue_len' failed.

    "This":https://bugreports.qt-project.org/browse/QTBUG-31935 bug seems to be the same. Neither of the proposed solutions (calling XinitThreads(), or patching libxcb as directed, or both) solves the problem - the patched version just causes a segfault down the line instead of failing the assertion.

    The bug is closed (because it's not a Qt bug) and the only relevant bug in xcb is similarly closed (they don't think it's xcb's fault either).

    The problem only appears to occur on my laptop (using integrated graphics / mesa gl), all on Ubuntu 13.10.

    Any help would be appreciated!


  • Moderators

    You can find a bit more experienced low level hackers on the Qt Interest mailing list. Maybe somebody would have an answer for you there.


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