QThreadStorage crash in Windows - 4.7.0

kartlee

Hi,

I am using QThreadStorage for to store thread specific data and boost threads to spawn desired number of threads. I get a strange crash in Windows [ Version 6.0.6002 ] in QThreadStorage's hasLocalData(). Below is the stack trace of the crash -

@QtCore4.dll!6701c468()
[Frames below may be incorrect and/or missing, no symbols loaded for QtCore4.dll]
QtCore4.dll!6701efa5()
QtCore4.dll!6701f010()
QtCore4.dll!6701ea6a()

testc.exe!QThreadStorage<TEST >::hasLocalData() Line 140 + 0x10 bytes C++
testc.exe!test_log_stream() Line 35 + 0xc bytes C++
testc.exe!test_thread_run() Line 51 C++
testc.exe!boost::detail::thread_data<void (__cdecl)(void)>::run() Line 57 C++
testc.exe!boost::`anonymous namespace'::thread_start_function() + 0x5b bytes C++
msvcr90.dll!_callthreadstartex() Line 348 + 0x6 bytes C
msvcr90.dll!_threadstartex(void * ptd=0x00d41fe0) Line 326 + 0x5 bytes C
kernel32.dll!7755eccb()
ntdll.dll!77b0d80d()
ntdll.dll!77b0da1f()@

We are using Qt 4.7.0 built with VS 2008. Here is the below code to reproduce the crash -

@#include <QtCore/qcoreevent.h>
#include <boost/thread.hpp>

#include <iostream>
#include <sstream>
#include <list>
using namespace std;

#include <stdlib.h>

class TEST
{
public:

int range_error;

 TEST()
{
    range_error = 0;
}

~TEST()
{   
}

};

Q_GLOBAL_STATIC(QThreadStorage<TEST*>, tlsTEST)

/***************************************************************************/
void test_log_stream()
{
TEST inst;
if(!tlsTEST()->hasLocalData())
{
inst = new TEST();
tlsTEST()->setLocalData(inst);
}
inst = tlsTEST()->localData();
inst->range_error = 1;
}

/**************************************************************************/
void test_thread_run( void )
{

test_log_stream();
return;
}

int main( int argc, char ** argv )
{

int num_of_threads = 40;

list<boost::thread *> threadList;
for(int i = 0; i < num_of_threads; ++ i)
threadList.push_back(new boost::thread(test_thread_run));

list<boost::thread >::iterator it;
for(it = threadList.begin(); it != threadList.end(); ++ it)
{
boost::thread t = *it;
t->join();
}

return 0;

}@

If I am doing anything wrong in the usage of tls, please let me know.

-Kartlee

andre

Any chance of upgrading to 4.7.3 to check if the issue remains in that version? It is just a patch upgrade from 4.7.0...

kartlee

Hi Andre,

Thanks for your reply.

I will check in 4.7.3 as you said. Do you see any issue in the code? (Or) aware of issues in Qt 4.7.0 with tls?

-Kartlee

kartlee

I get the same crash even in 4.7.3.

-Karthik

goetz

This is a warning in the source of [[Doc:QThreadStorage]]:

bq. QThreadStorage can only be used with threads started with QThread

So, I suspect this to be the cause of your problems.
Also, a Q(Core)Application is not running, which may cause problems too.

kartlee

Hi,

Thanks for your reply.

What you mentioned was clearly mentioned as a caveat in 4.2 -

http://doc.qt.nokia.com/4.2/qthreadstorage.html

But this is no longer mentioned in 4.7 -

http://doc.qt.nokia.com/4.7/qthreadstorage.html

Should we not take it for granted that it works with non Qt threads?

-Karthik

goetz

[quote author="kartlee" date="1314379149"]
Should we not take it for granted that it works with non Qt threads?
[/quote]

As the warning is still in the source code, I would say no, it only works with QThread, but not with with threads started using platform-specific APIs or other libraries like boost.