C / C++ / MFC

27-Jul-06 2:37

Hi,

I have used CRITICAL_SECTION to make my code thread safe and I was wondering if there is some way of testing it. I can call the code from two different threads and the code doesnt appear to screw up - but how do I really know that the cricial sction has blocked one thread until the other has completed rather than just being (un)lucky and both threads never actually called at the same time?

Is there something I can put in there to record that two threads have attempted to access the same resource?

TIA

Tony Smile | :)

Re: Testing Critical Sections [modified]

Cedric Moonen27-Jul-06 3:08

Cedric Moonen

27-Jul-06 3:08

Do you always test things like that ? Did you check if the if/else statments were doing their job, or if CreateThread is really creating a new thread Unsure | :~

?
Seriously, if you use them like it is documented, they will work how it is documented. No need to be paranoid Hmmm | :|

Cédric Moonen
Software developer

Charting control

softwaremonkey27-Jul-06 3:28

27-Jul-06 3:28

Hi,

Thanks for the reply.

Yes I do like to test stuff like that - I try to test all my code, including whether my if/else's do what I expect them to do. Not that I don't trust the compiler, but I sometimes write stuff that doesn't work - maybe its just me Sigh | :sigh:

So if I understand your correctly, if I 'think' I understand the documentation and it 'appears' to work - then it must be OK - non need to test it right? Laugh | :laugh:

I just wnated to make sure that my code is robust, no corruptions - no deadlocking - that kind of stuff. Then I can sleep at night.

Cheers Cool | :cool:

Tony

-- modified at 9:38 Thursday 27th July, 2006

Cedric Moonen27-Jul-06 3:42

Cedric Moonen

27-Jul-06 3:42

You sqid this:

softwaremonkey wrote:
but how do I really know that the cricial sction has blocked one thread until the other has completed rather than just being (un)lucky and both threads never actually called at the same time?

I understood that you wanted to check if the critical section were working properly, not your code. In that case, I think it is a litle bit useless to verify things that are used by milion of people Wink | ;)

But I understand now (yes, I know, my brain is slow today Poke tongue | ;-P

) that you want to check your code. Something that comes to my mind: in your thread, you can simply make a very lenghty operation (like a double for loop) that is inside a locked section. Then, with the other thread, wait that the critical section is freed. Log the times in a file to see if the second thread is really waiting for the critical section. Of course this is a basic scenario but you can improve it (e.g. use a lenghty operation in both threads)

Cédric Moonen
Software developer

Charting control

softwaremonkey27-Jul-06 4:10

27-Jul-06 4:10

Hi,

Thanks, I will try that.

Incidentally, I came across this intersting article about testing critical sections...

http://msdn.microsoft.com/msdnmag/issues/03/12/CriticalSections/default.aspx

It also has some code for some kind of debugging tools. I havent checked it out yet - still reading the article.

Thanks again for the help.

Tony Big Grin | :-D

peterchen27-Jul-06 4:18

peterchen

27-Jul-06 4:18

A simpler test:

have a volatile bool variable with global lifetime, visible in the critical section of code.
Initialize to zero before you start the thread(s).

Directly after Lock, check reentrancyFlag == 0
set flag to 1
Upon exit, set to 0
Make sure that you never forget to reset to zero even if you exit early through return or exception (e.g. through a scopeguard[^])

For a very critical test, put a Sleep() into the protected block 8debug build only, of course), so that overlaps are much more likely.

Some of us walk the memory lane, others plummet into a rabbit hole

Tree<t> in C# || Fold With Us! || sighist

S. Senthil Kumar27-Jul-06 5:07

S. Senthil Kumar

27-Jul-06 5:07

If you are running under a debugger, you could always manipulate two threads so that one gets into the critical section and waits (In VS .NET 2003, Right click on Threads Pane and click Freeze) , while you switch to the second thread. Then, you can allow the second thread to run. You should be able to know immediately whether the second thread blocks.

Regards
Senthil
_____________________________
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softwaremonkey27-Jul-06 6:24

27-Jul-06 6:24

Thanks for the replies guys,

If anyone is interested, I have also found that you can check the LockCount member of CRITICAL_SECTION to see if a thread is already in the critical section.

LockCount == -1 if the critical section is not already in use e.g.

if(lock.LockCount >= 0)
{
TRACE("Locked\n");
}

Tony Wink | ;)

GUO in DOS

rajeevktripathi27-Jul-06 2:25

rajeevktripathi

27-Jul-06 2:25

Hi All

I have to create a GUI in turbo C++ for Dos.
and I want to give Windows like look in interface.
so can you please tell me any library for GUI which could be used in DOS.

or tell me any better approach.

Thanks
Edit/Delete Message

#realJSOP27-Jul-06 2:34

#realJSOP

27-Jul-06 2:34

Use Borland C++ 2.0 (or maybe 3.0). It comes with TurboVision. I believe 3.0 could produce oth Windows and DOS apps.... it's been over 15 years since I did a DOS app...

"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass..." - Dale Earnhardt, 1997
-----
"...the staggering layers of obscenity in your statement make it a work of art on so many levels." - Jason Jystad, 10/26/2001

_AnsHUMAN_ 27-Jul-06 2:35

_AnsHUMAN_

27-Jul-06 2:35

Humm, this seems Hard to do with TurboC++.
See here for some help[^]

Somethings seem HARD to do, until we know how to do them.
Wink | ;-)

_AnShUmAn_

Re: GUO in DOS [modified]

Monty²27-Jul-06 2:37

Monty²

27-Jul-06 2:37

rajeevktripathi wrote:
I have to create a GUI in turbo C++ for Dos.
and I want to give Windows like look in interface.

Never thought i'd hear this Unsure | :~

rajeevktripathi wrote:
or tell me any better approach.

Use Windows

Help your local Search & Rescue. Get lost!

#realJSOP27-Jul-06 3:32

#realJSOP

27-Jul-06 3:32

Monty2 wrote:
Use Windows

He's already stated that he needs to write a DOS app, so it's obviously a *requirement* over which he has no control. People that come here and state their requirements aren't typically in the mood for off-the-cuff bullshit answers like yours.

-- modified at 9:54 Thursday 27th July, 2006

rajeevktripathi27-Jul-06 3:45

rajeevktripathi

27-Jul-06 3:45

Thanks U all

OK I will start to write such programs
can u please guide me how to proceed

But would like to tell the reason whiy I need ..
Infact working on such project where if system is crashed then system will be started with a bootable floppy ( in DOS mode) and our application will be invoked so wanna write GUI code for that part..

Please help me
Thanks

#realJSOP27-Jul-06 3:55

#realJSOP

27-Jul-06 3:55

Telling you how to write an application is WAY beyond the scope of this forum.

Joe Woodbury27-Jul-06 10:38

Joe Woodbury

27-Jul-06 10:38

Isn't that called Windows 3.0?

More seriously, when I did DOS programming, there were several graphics libraries, UI toolkits and other such things available. Unfortunately, not only are the obsolete, most the companies don't exist any more. (I last evaluated one of these libraries in 1989--the name "GreenLeaf" pops into mind--if they are who I remember them to be, contact them and see if they have some archived stuff they can sell you.)

A big problem is finding products that actually have drivers for DOS (this was the big bugaboo when doing this; you had to ship with a ton of graphics drivers and hoped that the user knew which one they were using since there was no standard detection method [somewhere, I have the code to detect if you were running Hercules mono, CGA, EGA or VGA graphics.])

Anyone who thinks he has a better idea of what's good for people than people do is a swine.
- P.J. O'Rourke