[Interest] Crash in QAbstractEventDispatcher::filterNativeEvent when trying to show a QMessageBox

Henry Skoglund henry at tungware.se
Thu Apr 14 23:52:42 CEST 2022

On 2022-04-14 23:15, Thiago Macieira wrote:
> On Thursday, 14 April 2022 12:02:06 PDT Henry Skoglund wrote:
>> if I look at the debugger data and in the QThreadData * dump, I see that
>> the looplevel is 1 but if this is the GUI thread shouldn't it be 2
>> considering we've passed through the exec() call in QDialog? I mean
>> since a Qt GUI app usually starts with an exec() call which changes the
>> looplevel from 0 to 1 for the lifetime of the app.
>> Is that why you're suspecting the crash occurs becase we're still in the
>> worker thread?
> Hello Henry
> You can't trust that data dump. The very first pointer in it is suspicious:
>> - d 0x0000020000030600
> That doesn't look like a valid pointer to me. However, I confess I don't know
> for sure because that's a Windows pointer and I don't know the memory layout
> on Windows as well as I do on Linux. Points in favour of it being valid are:
> ...
Indeed it looks weird (it's pointing into 2TB territory) but I believe 
it's just an effect of Microsoft's Control Flow Guard (tm) being active 
for that .exe.

Thanks for the analysis!

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