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.