Run-time error "index out of range"

ruehlchr

Hi all,

I fighting with a nasty problem on my Windows port (VS2008/VC++v9) for a test-tool with 2 threads.
To give you an overview what I did:

MainThread (keeps fingers on the Display/Input-Events)
WorkerThread (did some serial communication)

MainThread send commands by QQueue to the WorkerThread to tell what command to execute.
WorkerThread uses signal/slot to update the MainThreads QListWidget, QTextEdit, QLineEdit ....

What happen under Windows, the WorkerThread use a signal to clear a logging window (QListWidget). Next it write some debug
info's into it. ASSERT QVector<T>::at: "index out of range". (SOMETIMES)

When I debug the session and go back in the call-stack and check the variables i(1) and d->size(20) the Assert condition
not match any more ( i > 0 && i < d->size ).

My workaround I sleep for 200ms after the QListWidget::clear() before I continue with the program.

Not working: use a Mutex to protect the update calls in the MainThread to manipulate the display.

Mainthread queue in:
@
void Reader::freqSetPreset()
{
Cmd cmd;
cmd.cnum = Cmd::PRESETFREQ;
cmd.freqMode = ( cbFrePreset->currentIndex() & 0xff );
_thread1.queueCmd(cmd);
}
@

WorkerThread Dequeue
@
worker::run(){
....
forever {
_mutex.lock();
if ( _run ) {
_mutex.unlock();
if ( _cmdqueue.isEmpty() ) {
usleep(100);
}
else {

_queuemutex.lock();
Cmd cmd = _cmdqueue.dequeue();
_queuemutex.unlock();

...
switch ( cmd ) {
case Cmd::PRESETFREQ:
{
qDebug("Thread1 PresetFeq");
clearlog();
// workaround
usleep(200000);
freqSetPreset(cmd.freqMode);
break;
}

...

void Worker::freqSetPreset(const quint8 FreMode)
{
...
if ( _rmu.SetFrequency( FreMode, FreBase, BaseFre, ChannNum, ChannSpc, FreHop ) ) {
updateStatus("Preset Frequency\tOK"); // signal
}

@

successions welcome.

Chris

Franzk

Where exactly in the above code does your program crash?

ruehlchr

Franz,

I need to start the thing in the Virtual Studio ( ;-( ) ) then I can tell exactly.

General
a) QListWidget::clear()
b) QListWidget::addItem(s) QString s

sender WorkerThread via signal to receiver MainThread slot.

I never face the problem on the Linux.

goetz

Could be an issue with non-queued signals between threads. Did you read Peppe's great wiki article "Threads, Events and QObjects":http://developer.qt.nokia.com/wiki/Threads_Events_QObjects already? It explains a lot of stuff in this area.

ruehlchr

Volker,

That's a succession ..
thanks I will dig in - windows macht mich fertig!.

But its 6:15pm in Hong Kong now and I go and have a beer. This problem needs to wait until tomorrow , but I let you know.

Cheers
Chris

goetz

Enjoy your "Feierabend" :-)

ruehlchr

Hi All,

I found the my problem. The Logging !
I have my own MessageOutHandler .. this Handler wrote non synchronized directly to the ListWidget and triggers the ASSERT() .. - no need for the work around any more.

Volker the article you refer was very nice. Some of the infos help me find my fault.

cheers
Chris