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Heads up: Setting the Qt::WA_MacAlwaysShowToolWindow flag might cause crashes in macOS 10.13 and 10.12

  • I don't have time to track down what really happened, so instead I just post this topic here in case anyone has problems with crashes on 10.13 and 10.12. The problem was not so notable when I used Qt 5.7.1, but when I upgraded to Qt 5.10.0, my program crashed almost instantly in 10.13 (which was good). I also got crash reports on 1012, although I wasn't able to make 10.12 crash myself.

    Anyway, after A LOT of investigation, I finally found the cause, and as you see below, the backtrace isnt't much help.

    4   libsystem_platform.dylib            0x00007fff60a79f5a _sigtramp   26
    5   ???                                 0x000000014f3fc080 0   5624545408
    6   libqcocoa.dylib                     0x0000000108ee2524 0x108eba000   165156
    7            0x00007fff3920d1ac __CFNOTIFICATIONCENTER_IS_CALLING_OUT_TO_AN_OBSERVER__   12
    8            0x00007fff3920d09a _CFXRegistrationPost   442
    9            0x00007fff3920cde2 ___CFXNotificationPost_block_invoke   50
    10            0x00007fff391cb972 -[_CFXNotificationRegistrar find:object:observer:enumerator:]   1826
    11            0x00007fff391caa0c _CFXNotificationPost   652
    12                0x00007fff3b2a3477 -[NSNotificationCenter postNotificationName:object:userInfo:]   66
    13                    0x00007fff36c238c2 -[NSApplication _handleActivatedEvent:]   714
    14                    0x00007fff36f9da39 -[NSApplication(NSEvent) sendEvent:]   2969
    15  libqcocoa.dylib                     0x0000000108ee720d 0x108eba000   184845
    16                    0x00007fff367ff28d -[NSApplication run]   812
    17  libqcocoa.dylib                     0x0000000108ee4333 0x108eba000   172851
    18  QtCore                              0x000000010346cc87 QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>)   325
    19  QtCore                              0x00000001034707a2 QCoreApplication::exec()   276

  • Lifetime Qt Champion

    @kmatheussen if you want to get it fixed, you should report the issue on

    They might ask you for a minimal reproduceable example, though.


  • Yeah, maybe later. As I wrote, I don't have time now. The program is several hundred thousand lines long, and this line was in a general utility function that could have been called from a lot of places, so it's a lot of work to create a minimal example.

  • Also, I'm happy now. I don't need a fix. This is just a heads up post for others who might have the same problem.

  • Lifetime Qt Champion

    Good work finding it in such large program :)

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