Re: Thread killing problem

From:

"J.K. Baltzersen" <jornbalt@pvv.org>

Newsgroups:

comp.lang.c++

Date:

Wed, 26 Dec 2007 09:57:10 -0800 (PST)

Message-ID:

<c6be5f7d-ac03-4cee-82d7-6ecd1cbf1659@r60g2000hsc.googlegroups.com>

On Dec 26, 4:49 pm, yanlinlin <yanlinli...@gmail.com> wrote:

On Dec 26, 10:10 pm, "J.K. Baltzersen" <jornb...@pvv.org> wrote:

On Dec 26, 3:01 pm, "J.K. Baltzersen" <jornb...@pvv.org> wrote:

On Dec 26, 2:04 pm, yanlinlin <yanlinli...@gmail.com> wrote:

On Dec 26, 7:20 pm, "J.K. Baltzersen" <jornb...@pvv.org> wrote:

On Dec 26, 12:00 pm, yanlinlin <yanlinli...@gmail.com> wrote:

On Dec 26, 5:42 pm, "J.K. Baltzersen" <jornb...@pvv.org> wrote:

To whomever it may concern:

I am using MS Visual C++ 6.0.

I have a process A which instantiates an object C.

At a later point the process A creates the thread B.

The thread B has access to the object C.

Because the user cancels the "process" which the thread B hand=

les, the

thread B is stopped by the use of TerminateThread.

A bit later on I try to access member variables in the object =

B, the

purpose of this being replacing some files with backup version=

s of

these same files. These member variables are of type std::stri=

ng.

Let's call these m, n, and o. When I access m, there seems to =

be no

problem. However, when I access n, the debugger hangs, apparen=

tly

infinitely.

I tried replacing std::string with char*, but that only result=

ed in

the problem showing up when I accessed m.

I want to be able to run TerminateThread on the thread B witho=

ut my

object C being corrupted.

I would greatly appreciate any tips that would lead to my bein=

g able

to do so.

Thank you very much in advance for any help.

Best regards,
J.K. Baltzersen

Don't use TerminateThread. Use event or something else to notify=

the

thread to exit by itself instead.- Hide quoted text -

- Show quoted text -

My thread is not event oriented. It runs from start to end unless =

some

exception is thrown. Could I tell the thread to throw an exception=

, by

sending a message to it, at an arbitrary point? I would rather avo=

introducing checkpoints where the thread decides whether to contin=

or exit.

Thanks again.

Sorry to misguide you. What I mean about the event is not the event
supported by OS, but just a notification.
Maybe you can do it like this:

volatile bool flag = false; // this is a global variable for notif=

ying

DWORD WINAPI TheThreadProc(LPVOID) // this is the thread proc
{
   // ...
   while ( ! flag)
   {
      // ...
      if (flag) break;
      // ...
   }
   return 0;

}

void Foo()
{
   HANDLE hThread = CreateThread(...);
   // ...
   flag = true; // Set the variable to let the thread exit by =

itself

WaitForSingleObject(hThread);
// ...

}

Since TerminateThread can not guarantee variables in thread be
destroied correctly, let the thread exit by itself is the right way.=

- Hide quoted text -

- Show quoted text -

Thanks.

However, redesigning this application to check for an exit flag at
every second (or whatever we might choose) would be very costly. So I
was hoping there could be a simpler way, such as sending an exception
to the thread that is to exit. In that way we would be using the
existing exception handling system. The thread would exit upon
catching the exception.

Again, thanks.- Hide quoted text -

- Show quoted text -

I've tried a solution with SuspendThread as well. There seems to be
some of the same problems with that. I've also thought about putting
the thread to sleep for such a long time that it won't wake up before
the entire process has exited. However, I haven't found a way of
putting a thread to sleep from outside.

Use ResumeThread to wake up the suspened thread. Or use CreateEvent
and WaitForSingleObject instead of sleep for long time.- Hide quoted text =

- Show quoted text -

When I try to access the member variables of object C while thread B
is under suspension, I get the same problem -- seemingly at least --
as I get when I have terminated the thread with TerminateThread.