C / C++ / MFC

Rama Krishna Vavilala30-May-02 7:23

Rama Krishna Vavilala

30-May-02 7:23

1. Select the menu Project->Add Class

2. In the dialog box that appears. Select MFC class From ActiveX control

3. In the next dialog select the ActiveX control you want.

BTW, I don't think using MFC Wrappers around ActiveX controls is a good idea. I much rather recommend using #import the typelibrary.

Mazdak30-May-02 9:20

Mazdak

30-May-02 9:20

Michel Prévost wrote:
Microsoft DataGrid Control 6.0 (OLEDB)

I don't think this component exist in VC7.

Mazy

"The more I search, the more my need
For you,
The more I bless, the more I bleed
For you."The Outlaw Torn-Metallica

Le centriste30-May-02 9:28

Le centriste

30-May-02 9:28

Yes, it does. I followed Rama's instructions and I found it.

Michel

It is a lovely language, but it takes a very long time to say anything in it, because we do not say anything in it, unless it is worth taking a very long time to say, and to listen to.

- TreeBeard

Worker Threads and GetExitCodeThread()

Mazdak30-May-02 21:16

Mazdak

30-May-02 21:16

Michel Prévost wrote:
I followed Rama's instructions and I found it.

But it does not exist in my computer.I don't think its thr part of default installation in VS.Net.

Chris Meech30-May-02 6:36

Chris Meech

30-May-02 6:36

If I am using some code as follows

aThreads[iArrayIndex] = AfxBeginThread(ClientExtractThread, (LPARAM)pExtractor);
...
...
iArrayIndex = WaitForMultipleObjects(MAX_CONCURRENT_THREADS,aThreads,FALSE,INFINITE);
...
...
GetExitCodeThread(aThreads[iArrayIndex]->m_hHandle, &nRetVal);

I'm concerned that the member variable m_bAutoDelete of the CWinThread object created by AfxBeginThread, which defaults to TRUE, will cause the GetExitCodeThread call to not function correctly. Alternatively I can set this member to FALSE, but then I don't know what I have to clean up? Should I just call delete after the GetExitCodeThread has finished.

delete (CWinThread*)aThreads[iArrayIndex];

Thanks for any suggestions.

Chris

Prem Kumar30-May-02 7:11

Prem Kumar

30-May-02 7:11

As you have said you can delete the CWinThread object safely
after you have got the Exit Code.

Chris Meech30-May-02 7:25

Chris Meech

30-May-02 7:25

Thanks Prem.

Tomasz Sowinski30-May-02 13:16

Tomasz Sowinski

30-May-02 13:16

If you set m_bAutoDelete to TRUE, your thread will delete yourself. The value of 'aThreads[iArrayIndex]' in GetExitCodeThread call points to freed memory block and there's absolutely no guarantee that m_Handle contains valid value.

In short, you shouldn't use m_bAutoDelete --or-- you should store thread handles in other location.

Tomasz Sowinski -- http://www.shooltz.com

- It's for protection
- Protection from what? Zee Germans?

"Scalar deleting destructor" error

Chris Meech31-May-02 2:22

Chris Meech

31-May-02 2:22

Thanks Tomasz. You always have some good insight to offer.

I do end up having to store the thread handles in an other array since I need to pass an array of thread handles to the WaitForMultipleObjects call that I make.

Additionally, I am going to use m_bAutoDelete. But I'm going to set it to FALSE, so that when the thread completes, I can call still call GetExitCodeThread and the thread handle should still be valid. After getting the exit code value, I will then 'delete' the thread.

Thanks for the comment.

Chris

Jason Hihn30-May-02 6:07

30-May-02 6:07

I have code that looks like:
CArray<obj *,="" obj="" *=""> ArrayOfObjPtrs;
ObjPtr op=new Obj();

ArrayOfObjPtrs.Add(op);

Then in another function called later in the same thread, I do:

delete ArrayOfObjPtrs.GetAt(0); // free the object ** run-time error on this line **
ArrayOfObjPtrs.RemoveAt(0);

the Run-time error is in MSVCRTD, but the last call of mine is on the stack right before it, is "Obj::`scalar deleting desctructor' (unsigned int 1) + 56 bytes

I get a Debug Asseertion:
dbgdel.cpp Line 47, Expression _BLOCK_TYPE_IS_VALID(pHead->nBlockUse)

Can anyone please tell me what is going on? Thanks soooo much!

PS. Commenting out the 'delete' line results in a memory leak

Prem Kumar30-May-02 7:14

Prem Kumar

30-May-02 7:14

Probabaly you could remove the element first and then delete it next using an
intermediatery temp variable.

Jason Hihn30-May-02 7:19

30-May-02 7:19

What effect would that have?

Rama Krishna Vavilala30-May-02 7:25

Rama Krishna Vavilala

30-May-02 7:25

How does the class ObjPtr look? Looks to me that there is some sort of a casting problem.

I feel that ArrayOfObjPtrs.GetAt(0) is not returning Obj* for some reason.

Jason Hihn30-May-02 7:53

30-May-02 7:53

new() returns a pointer This pointer to the object, not the object itself, is stored in the CArray

Rama Krishna Vavilala30-May-02 8:02

Rama Krishna Vavilala

30-May-02 8:02

What is ObjPtr is it a class or there was a typo in the original mail

ObjPtr op = new Obj();

or is it

Obj* op = new Obj();

How does you ObjPtr class look?

Jason Hihn30-May-02 7:58

30-May-02 7:58

Im my example, they both are the same. ObjPtr is a Obj *

Sorry for the abiguity.

Bill Wilson30-May-02 11:53

Bill Wilson

30-May-02 11:53

Try telling the CArray what kind of thing you will be storing in it. For example if you were storing pointers to CString objects, you would define it like this:

CArray<cstring *,="" cstring="" *=""> myArray;

wqw31-May-02 2:14

wqw

31-May-02 2:14

i usually get this error when trying to delete a ptr to an object allocated on the stack. you'll have to check your code (esp. typedef's in yout case: ?ObjPtr?)

HTH,

a really simple question (i think)

31-May-02 2:42

Hope u're not doing something like: delete this; within the destructor. It may have destroyed the pointer when u exited the function within which u did the allocation. That's a rather strange characteristic of C++. If that's not the case then u may have destroyed the object somewhere else without realizing it,otherwise there's no reason the above code should throw that exception.

vb_200230-May-02 5:01

vb_2002

30-May-02 5:01

IN VC++ 6. how do you 'Watch' an entire array - Not just the individual elements.

Prem Kumar30-May-02 5:09

Prem Kumar

30-May-02 5:09

1. Watch in the memory window
2. List all individual elements in the watch window

Paul M Watt30-May-02 5:29

Paul M Watt

30-May-02 5:29

If you open up the watch window, you can type in the name of the array. Then you will be able to click on the plus button to the left of the array and expand all of its elements.

Build a man a fire, and he will be warm for a day
Light a man on fire, and he will be warm for the rest of his life!

vb_200230-May-02 5:54

vb_2002

30-May-02 5:54

The array was allocated dynamically...wud that be the reason why, when I click the + sign, it shows only the first element and not all of them ?

Paul M Watt30-May-02 7:05

Paul M Watt

30-May-02 7:05

Yes, that would be the problem. The debugger is not quite sure how long your buffer is. In that case you can qualify your data by placing a comma (,) after the name of your pointer, and the number of elements that you want to watch.

Build a man a fire, and he will be warm for a day
Light a man on fire, and he will be warm for the rest of his life!