Re: Threads - C / C++ / MFC Discussion Boards

Eytukan12-Sep-05 4:50

12-Sep-05 4:50

i'm trying to run two separate threads. its working when i use an Integer to be passed as an argument to the thread. for example, if i send '1' one thread will keep on telling 1,1,1,1,1,1,1.

[tested using msgbox]

mean while, i send '2'. then another instance of the thread will start saying 2,2,2,2,2,2,

so u will get like 1,2,1,2,1,2,2,1,2,1,1.. like that.. its woking fine.

But if i pass a char[] parameter, its not working Frown | :(

ie,

if i pass "TEST",
it says , "TEST","TEST","TEST".......

meanwhile if i start another to say "CODE",

its destroys "TEST" and so two instance of "CODE" is displayed.
like instead of "TEST","CODE","TEST","CODE",... am getting like "CODE","CODE","CODE"...

plz tell me how to go..
thanks in advance

Thanks in advnace
V

Re: Threads

John M. Drescher12-Sep-05 5:52

John M. Drescher

12-Sep-05 5:52

Vivekuniq wrote:
plz tell me how to go.

You need thread synchronization for this to work. Place a critical section or mutex around your display routine so that only one thread can print at one time.

John

Re: Threads

Eytukan12-Sep-05 7:59

Eytukan

12-Sep-05 7:59

but how is it working for Integers?

V

Re: Threads

John M. Drescher12-Sep-05 8:03

John M. Drescher

12-Sep-05 8:03

Without the code I can only guess... So here is my best guess: Because the code to output the integers takes so fast that there is no context switch between the call.

John

code

Eytukan12-Sep-05 8:15

Eytukan

12-Sep-05 8:15

if there is no context switch , it should print the same value right?.. sorry if i misunderstand, anyway plz view the code here.. plz try to help me . everytime i'm struggling with the threads Frown | :(

.

char[4] agIndv;

UINT CQACDDlg::DevMonitoring(LPVOID p)
{
CQACDDlg * me = (CQACDDlg *)p;
me->DevMonitoring(agIndv);
return 0;

}

void CQACDDlg::DevMonitoring(char[] ageID)
{
while(1)
{
AfxMessageBox(ageID);
//Sleep here for a while
}

}

void CQACDDlg::OnSetSplit() // onclick for new Threads
{
m_SplitID.GetWindowText(agIndv,5); //agIndv is global taken from a CEdit box
AfxBeginThread(DevMonitoring,this);

}

in the header file,
i declare
static UINT DevMonitoring(LPVOID lp);

V

Re: Threads

David Crow12-Sep-05 6:25

David Crow

12-Sep-05 6:25

The objects passed to the threads should probably be allocated on the heap rather than the stack, and then destroyed by the secondary thread. Something like (in MFC):

CString *strName = new CString("David");
AfxBeginThread(ThreadProc, strName);
...
UINT ThreadProc( LPVOID lpVoid )
{
    CString *str = (CString *) lpVoid;
    ...
    delete *str;
    return 0;
}

The same concept can be used with non-MFC code.

"One must learn from the bite of the fire to leave it alone." - Native American Proverb

Re: Threads

Eytukan12-Sep-05 8:10

Eytukan

12-Sep-05 8:10

can you tell me in context with the below code?
char[4] agIndv;

UINT CQACDDlg::DevMonitoring(LPVOID p)
{
CQACDDlg * me = (CQACDDlg *)p;
me->DevMonitoring(agIndv);
return 0;

}

void CQACDDlg::DevMonitoring(char ageID[])
{
while(1)
{
AfxMessageBox(ageID);
}

}

void CQACDDlg::OnSetSplit() // OnClick for new Threads
{
m_SplitID.GetWindowText(agIndv,5); //agIndv is global taken from a CEdit box
AfxBeginThread(DevMonitoring,this);

}

Thanks
V

Re: Threads

Bob Stanneveld12-Sep-05 8:44

Bob Stanneveld

12-Sep-05 8:44

Hello,

If I see correct, you have a global instance of a char array. I guess that you use that array to write "TEST" and "CODE" to, that are passed to the thread.

Your problem is that you overwrite the contents of the array. So both threads are printing the same array!

To solve this problem, allocate a char array on the heap and pass that to the threads:

UINT CQACDDlg::DevMonitoring(LPVOID p)
{
    CQACDDlg * me = (CQACDDlg *)p;
    char* psAg = new char[/*length of string*/];
    // copy string contents to psAg
    me->DevMonitoring(psAg);
    return 0;
}

void CQACDDlg::DevMonitoring(char* pszAgeID)
{
    while(1)
        AfxMessageBox(ageID);
    delete[] pszAgeID;
}

Behind every great black man...
... is the police. - Conspiracy brother

Blog[^]

Re: Threads

Eytukan12-Sep-05 22:20

Eytukan

12-Sep-05 22:20

Bob Stanneveld wrote:
Behind every great black man...
... is the police. - Conspiracy brother

Behind every great piece of code in this application is
......BOB and David- VivekUniq

EXCELLENT. thank u so much. Smile | :)

Re: Threads

Bob Stanneveld13-Sep-05 1:25

Bob Stanneveld

13-Sep-05 1:25

Vivekuniq wrote:
EXCELLENT. thank u so much.

You're welcome Big Grin | :-D

Behind every great black man...
... is the police. - Conspiracy brother

Blog[^]

Re: Threads

David Crow12-Sep-05 8:55

David Crow

12-Sep-05 8:55

I'll try.

struct info
{
    CQACDDlg *pThis;
    char *string;
};
 
void CQACDDlg::DevMonitoring( LPSTR lp )
{
    while (1)
        AfxMessageBox(lp);
 
    delete [] lp;
}
 
UINT DevMonitoring( LPVOID lpVoid )
{
    struct info *me = (struct info *) lpVoid;
    me->pThis->DevMonitoring(me->string);
    delete me;
 
    return 0;
}
 
void CQACDDlg::OnSetSplit()
{
    struct info *s1 = new struct info;
    s1->pThis = this;
    s1->string = new char[5];
    lstrcpy(s1->string, "CODE");
    AfxBeginThread(::DevMonitoring, s1);
    
    struct info *s2 = new struct info;
    s2->pThis = this;
    s2->string = new char[5];
    lstrcpy(s2->string, "TEST");
    AfxBeginThread(::DevMonitoring, s2);
}

"One must learn from the bite of the fire to leave it alone." - Native American Proverb

Re: Threads

Eytukan12-Sep-05 22:27

Eytukan

12-Sep-05 22:27

Thank u so much man.. Smile | :)

.. i'm so happy Smile | :)

delete always goes with set NULL?

valerie9912-Sep-05 3:49

valerie99

12-Sep-05 3:49

Morning, all

Is it necessary to set the pointer to NULL after delete everytime in C++?
It would cause memory leak by just delete and NOT set to NULL, right?

Thank you!

Re: delete always goes with set NULL?

toxcct12-Sep-05 4:00

toxcct

12-Sep-05 4:00

valerie99 wrote:
Is it necessary to set the pointer to NULL after delete everytime in C++?

if you're about using the pointer variable again and want to be sure not to use an invalid memory block, yes, set to null.

valerie99 wrote:
it would cause memory leak by just delete and NOT set to NULL, right?

how ???? Unsure | :~

TOXCCT >>> GEII power
[toxcct][VisualCalc]

Re: delete always goes with set NULL?

David Crow12-Sep-05 4:28

David Crow

12-Sep-05 4:28

valerie99 wrote:
Is it necessary to set the pointer to NULL after delete everytime in C++?

It's not required, but it is recommended.

valerie99 wrote:
It would cause memory leak by just delete and NOT set to NULL, right?

No, not at all. The memory is freed within the delete operator. Setting the pointer to NULL afterwards is just a precautionary measure.

"One must learn from the bite of the fire to leave it alone." - Native American Proverb

Re: delete always goes with set NULL?

Nemanja Trifunovic12-Sep-05 4:28

Nemanja Trifunovic

12-Sep-05 4:28

valerie99 wrote:
Is it necessary to set the pointer to NULL after delete everytime in C++?

No, but it is considered "a good programming practice".

valerie99 wrote:
It would cause memory leak by just delete and NOT set to NULL, right?

No. It would not.

My programming blahblahblah blog. If you ever find anything useful here, please let me know to remove it.

Re: delete always goes with set NULL?

S. Senthil Kumar12-Sep-05 4:42

S. Senthil Kumar

12-Sep-05 4:42

valerie99 wrote:
It would cause memory leak by just delete and NOT set to NULL, right?

Out of curiosity, did you happen to program in a garbage collected environment?

Regards
Senthil
_____________________________
My Blog | My Articles | WinMacro

COleDateTime question

eli1502197912-Sep-05 3:47

eli15021979

12-Sep-05 3:47

Hi,
I'm using the COleDateTime control to allow the user to set the date.
My question is : How can i get the selected date by the user?
I know i should handle the MCN_SELECT message'but i don't know how to get the
selected date.

Anyone?

Regards,
Eli

Re: COleDateTime question

David Crow12-Sep-05 4:28

David Crow

12-Sep-05 4:28

eli15021979 wrote:
How can i get the selected date by the user?

By using any number of the Getxxx() methods:

GetMonth() // get month (1 - 12)
GetDay()   // get day (1 - 31)
GetYear()  // get year

"One must learn from the bite of the fire to leave it alone." - Native American Proverb

Re: COleDateTime question

eli1502197912-Sep-05 4:34

eli15021979

12-Sep-05 4:34

Hi David,

First,Thanks for your prompt reply.
I tried the Getxxx() method but the give me the current system time and not the selected date.

Regards,
Eli

Re: COleDateTime question

David Crow12-Sep-05 4:45

David Crow

12-Sep-05 4:45

This makes no sense. A COleDateTime object represents whatever date you set it to, be it some past date, the current date, or some future date The concept of 'selecting' a date, much like you would with a UI component, does not exist. You can 'set' the date, however.

"One must learn from the bite of the fire to leave it alone." - Native American Proverb

Re: COleDateTime question

eli1502197912-Sep-05 20:34

eli15021979

12-Sep-05 20:34

Hi David,

Thanks again for your answers.
It's my mistake - I've set the control class member to COleDateTime instead of CMonthCalCtrl.
with CMonthCalCtrl I can use the GetCurSel() to get the selected date.

With besr regards,
Eli

Re: COleDateTime question

David Crow13-Sep-05 2:08

David Crow

13-Sep-05 2:08

eli15021979 wrote:
with CMonthCalCtrl I can use the GetCurSel() to get the selected date.

Makes much more sense. Glad you are working now.

"One must learn from the bite of the fire to leave it alone." - Native American Proverb

Thread in VC++ !

lucdt12-Sep-05 3:08

lucdt

12-Sep-05 3:08

Hi all !
I have developed the application. in my main class, I call 8 thread . The main class must to wait all 8 Thread end to continute do something. How to known all 8 Thread ended ?

pls, help me !
Thank alots

Re: Thread in VC++ !

Niklas L12-Sep-05 3:18

Niklas L

12-Sep-05 3:18

You can use the WaitForMultipleObjects function using HANDLEs to your threads and setting bWaitAll to TRUE.

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.