Segmentation fault SIGSEGV, what can it be?

[jsulm]

You could try to change wbstlDevice to an instance variable instead of pointer and see whether is still crashes.

[Gerd]

The few lines of code you shown so far didn't seem to have any error.
As you where talking about asynchronus data filling this error may be thread-related.
How is the method in MainWindow called that deals with device ?

[StephanWoebbeking]

@jsulm I have made it an object member instead of a pointer now. Did the same to the "device" object which was a pointer before but which - I think - doesn't have much to do with it.

Anyway, both did not show any effect. I also added some initial data to the QByteArray in the constructor - this data is still there (the debugger shows it) when I want to add more data. Even, now I only add one more static byte - just to try it. Still I receive the segmentation fault...

No more ideas, anyone else?

Stephan

[StephanWoebbeking]

@Gerd Well, the object "device" is basically used everywhere in the mainwindow class as it holds some information used in a lot of cases. For the specific method I do call a slot using a signal, then its a method of the mainwindow and that has direct access to "device". As this holds the QByteArray I can access it without any (compiler) problems, but I get the segmentation fault...

Stephan

[Gerd]

As you are talking about multithreading did you try to use a queued connection when connecting the involved Signals/Slots?

[StephanWoebbeking]

Hi, me again...

I have run a quick test... removed the line of

device.rfPower4x1.append( 0x74 );

for

device.appendRfPower4x1( 0x74 );

Now, obviously I had to introduce this method like this:

void wbstlDevice::appendRfPower4x1(char data) {
    rfPower4x1.append( data );
}

The result is, that I still get a segmentation fault but this occurs actually a few lines further down - things that were working fine before??? I feels to me like there is some issue with thread safety, threads in general I am not completely aware off. Does that ring a bell for anyone?

Thanks,
Stephan

[StephanWoebbeking]

Could it be a problem in general, that I use "device" as a member variable of the "mainwindow" after I have connected one method of "mainwindow" to another? Now I tried both, to use "device" as a member variable and as an argument that I have transferred via the emit call. So there is multithreading coming into place, is there anything behind I haven't considered yet?

Stephan

[Gerd]

Look two posts above....

[StephanWoebbeking]

@Gerd Right, I still had this on my list to try it out... I have now changed the "connect" to this:

    connect( this,                      SIGNAL( rcvProdTestFromCOM( QString, QByteArray ) ),  this, SLOT( rcvProdTestFromCOMSlot( QString, QByteArray ) ), Qt::QueuedConnection );

From my perspective that's all I have to do to make it queued, right? Nothing else to change in the definitions for signals or slots?

Tried this out: Same effect, still get a segmentation fault... :-(

Can somebody confirm if there is any issue behind I may have overseen when using the SAME object in the code BEFORE calling EMIT and in the code of the SLOT?

Regards,
Stephan

[kshegunov]

This post is deleted!

[IvanC]

Hi, i was experiencing the same strange thing... i was using Qt headers and non Qt headers, and placing before the Qt headers seemed to have solved the problem.