C / C++ / MFC

Re: Question about how to kill thread that i create with _beginthreadex ?

10-Mar-08 20:40

Let the thread procedure function exit by itself.

Maxwell Chen

Peter Weyzen10-Mar-08 20:41

Re: Question about how to kill thread that i create with _beginthreadex ? [modified]

10-Mar-08 20:41

There's a few ways to do it.

The nice way:

Before starting the thread, create an event object (CreateEvent). Share this event handle with your thread, check it periodically -- and when it becomes signalled, have the thread exit itself. It's always best for the thread to exit gracefully.

HANDLE hEvent = CreateEvent();
_beginThreadEx( NULL, 0, YourThreadFunc, hEvent, 0, &ThreadID );

unsigned int __stdcall YourThreadFunc( LPVOID pData )
{
   HANDLE hEvent = (HANDLE)pData;
   while ( WaitForSingleObject(hEvent,0) != WAIT_OBJECT_0 )
   { 
       DoSomething();
   }
   return 0;
}

SetEvent(hEvent);

The nasty way:
TerminateThread( threadHandle );

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~<br />
Peter Weyzen<br />
Staff Engineer<br />
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Yanshof10-Mar-08 21:15

Yanshof

10-Mar-08 21:15

I cant in my code check for event ... but using TerminateThread look better option for now.
but I dont understand why dont use the TerminateThread ?
I rad about TerminateThread in MSDN - and they wrote "TerminateThread is a dangerous function that should only be used in the most extreme cases" - but i dont see any problem.

Can you explain ?

Thanks.

modified on Tuesday, March 11, 2008 3:31 AM

Re: Question about how to kill thread that i create with _beginthreadex ?

Cedric Moonen10-Mar-08 21:33

Cedric Moonen

10-Mar-08 21:33

Because it is not a natural way to exit your thread. First, if you allocated some resources in your thread, there's no way you will be able to clean them if you are using TerminateThread.
Second, you have no control about what you are doing: you will terminate the thread whatever it was processing. It means you can terminate it in the middle of something important that will be left not terminated (e.g. if you communicate with an external device, you started to send some data to it and then brutally stop it, leaving the device in an unknown state).

It is far better to handle that yourself, using a flag for example: you check regularly if this flag is false, if that's the case, you exit nicely the thread function (the general idea is having a loop that checks for this flag).

Cédric Moonen
Software developer

Charting control [v1.3 - Updated]

Re: Question about how to kill thread that i create with _beginthreadex ?

Yanshof10-Mar-08 21:39

Yanshof

10-Mar-08 21:39

Ok, now i see the problem

Thanks.

Re: Question about how to kill thread that i create with _beginthreadex ?

Peter Weyzen10-Mar-08 21:54

How virtual destructor works under the hood?

10-Mar-08 21:54

If this is your first jaunt into threading, you'll run into some problems. There's a whole bunch of things that you need to learn about in order to make threading work right.

But once you figure them out -- you'll LOVE threading!

The most important lesson is "Don't take shortcuts" -- a certain level of discipline is important when constructing a program that employs threads.

I think I've forgotten how to write an unthreaded program. What did we do before threading?

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~<br />
Peter Weyzen<br />
Staff Engineer<br />
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abhijitr10-Mar-08 19:41

abhijitr

10-Mar-08 19:41

Hi,

Can anybody please explain, How virtual destructor works under the hood?
What happens exactly with virtual table?

Thanks in advance.

Peter Weyzen10-Mar-08 19:47

10-Mar-08 19:47

I think:

The destructor goes into the vtable.

When the destructor is called -- the top-most constructor is called first, executed, then in turn, the each of the parent destructors are called. The order is the opposite of the order that the constructors are executed.

If you didn't do a virtual destructor, the parent destructors are hidden. I, personally, always use virtual destructors.

Just off the top of my head.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~<br />
Peter Weyzen<br />
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Rajkumar R10-Mar-08 23:53

Rajkumar R

10-Mar-08 23:53

Peter Weyzen wrote:
When the destructor is called -- the top-most constructor is called first

typo ?

Peter Weyzen11-Mar-08 7:46

11-Mar-08 7:46

sure seems like one!

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~<br />
Peter Weyzen<br />
Staff Engineer<br />
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Rajkumar R11-Mar-08 8:27

Rajkumar R

11-Mar-08 8:27

I assume you mean "When the (virtual)destructor is called -- the top-most ~~constructor~~ destructor is called first". If so, why don't you edit.

Peter Weyzen11-Mar-08 8:49

11-Mar-08 8:49

then your reply wouldn't make any sense.... and we don't want that!

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~<br />
Peter Weyzen<br />
Staff Engineer<br />
<a href="http://www.soonr.com">SoonR Inc -- PC Power delivered to your phone</a>

Maxwell Chen10-Mar-08 20:36

10-Mar-08 20:36

This article[^] for your reference.

Maxwell Chen

Missing Start Point

Member 461894910-Mar-08 18:29

Member 4618949

10-Mar-08 18:29

I have the following error

Error 1 error LNK2019: unresolved external symbol _WinMain@16 referenced in function ___tmainCRTStartup MSVCRTD.lib

I also have the WinMain defined and the subsystem set to Windows

and even the callign convention is __stdcall

Please help me urgently.. I am in need

Thanx in advance

Re: Missing Start Point

Maxwell Chen10-Mar-08 19:08

10-Mar-08 19:08

How does your WinMain prototype look like?

Maxwell Chen

Re: Missing Start Point

Sameerkumar Namdeo10-Mar-08 22:27

Sameerkumar Namdeo

10-Mar-08 22:27

Project properties ->
Linker ->
Advanced ->
Entry Point->
wWinMainCRTStartup

wWinMainCRTStartup ...if App is UNICODE
WinMainCRTStartup ... if App is not UNICODE

Worker thread->crash

lavate malllik10-Mar-08 17:39

lavate malllik

10-Mar-08 17:39

Iam having a MFC application, in which we have a worker theread.
Some operation is happens in worker thread.And we call this application for 10 times it works well.But when we call this application for 25th time it crashes at 25th time.

Let me know what will be the reasons behind this.
According to me one of the reasons is data type matching.But intially we resolved this problem for 10th time then it works well till. 24th time and at 25th time it crashes.

According to me there will be some other reaons behind this crashing.

Let me reasons how to rsolve this type of crashing.

lavatema

Stephen Hewitt10-Mar-08 18:00

Stephen Hewitt

10-Mar-08 18:00

We're not psychics. You haven’t provided enough information. What is the type of crash? Can you provide the call stack of the crash? Can you post the relevant code?

Steve

Peter Weyzen10-Mar-08 19:49

10-Mar-08 19:49

What does the debugger say?

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~<br />
Peter Weyzen<br />
Staff Engineer<br />
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ThatsAlok10-Mar-08 20:36

ThatsAlok

10-Mar-08 20:36

just try pinpoint the position where it is crashing, also just ?, are these 10 threads running syncronously, if yes, have you applied good sync logic!, if they sharing same data!

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Maxwell Chen10-Mar-08 20:45