Multithreading using AfxBeginThread

[kartikthakre]

I am creating thread using AfxBeginThread in Visual Studio 2005 and the first parameter of this function is function pointer so i am passing member function pointer of that class but it gives error i.e. my code is: AfxBeginThread( &CMultithreadingInDialogDlg::MyThreadProc, GetSafeHwnd() ); in which MyThreadProc is member function. and the error is error C2665: 'AfxBeginThread' : none of the 2 overloads could convert all the argument types. but it is working if i am passing function pointer of any static function or global function thanks in advance.

[David Crow]

Is MyThreadProc() a static member of CMultithreadingInDialogDlg?

"One man's wage rise is another man's price increase." - Harold Wilson

"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons

"Man who follows car will be exhausted." - Confucius

[Eugen Podsypalnikov]

kartikthakre wrote:

but it is working if i am passing function pointer of any static function or global function

That is also the "classical" way to pass - for example - a private static function of a dialog... :)

// .h
...
class CYourDialog : public CDialog
{
bool m_bWorking;
CWinThread* m_pcThread;
static DWORD WINAPI ThreadProc(CYourDialog*);
...
public:
CYourDialog(CWnd* pcParent = NULL);
~CYourDialog();
...
void On();
void Off();
...
};
// .cpp
...
CYourDialog::CYourDialog(CWnd* pcParent /*= NULL*/)
: CDialog(CYourDialog::IDD, pcParent),
m_bWorking(false),
m_pcThread(NULL)
{
...
}
CYourDialog::~CYourDialog()
{
Off();
}
CYourDialog::On()
{
if (!m_bWorking && !m_pcThread) {
m_bWorking = true;
m_pcThread = AfxBeginThread(ThreadProc, this);
}
}
CYourDialog::Off()
{
if (m_bWorking && m_pcThread) {
m_bWorking = false;
WaitForSingleObject(m_pcThread->m_hThread, INFINITE);
m_pcThread = NULL;
}
}
DWORD WINAPI CYourDialog::ThreadProc(CYourDialog* pcDlg)
{
while (pcDlg && pcDlg->m_bWorking) {
// Do something
Sleep(1);
}
return 0;
}

virtual void BeHappy() = 0;

modified on Thursday, April 1, 2010 2:42 AM

[Roger Stoltz]

Perhaps it's just a typo, but if not you should be aware of the following: There's a big risk the thread will never exit as you've failed to declare the m_bWorking variable as volatile. It depends on your optimization settings. The compiler may choose to hold the variable in a register in the while-loop, not reading it from its actual memory location since it's not being modified in the while-loop. Declaring it as volatile will tell the compiler that the variable must be read from its memory location and cannot be optimized into a register.

"It's supposed to be hard, otherwise anybody could do it!" - selfquote
"High speed never compensates for wrong direction!" - unknown

[Eugen Podsypalnikov]

Wow, I did not know it ! Thank you very much, Roger ! :) :thumbsup: As possible "workaround" could be also the usage of a limitation function:

bool CYourDialog::IsWorking() {
return m_bWorking;
}

virtual void BeHappy() = 0;

[Roger Stoltz]

Eugen Podsypalnikov wrote:

Wow, I did not know it ! Thank you very much, Roger !

:) You're most welcome.

Eugen Podsypalnikov wrote:

As possible "workaround" could be also the usage of a limitation function:

bool CYourDialog::IsWorking() {
return m_bWorking;
}

Naah, I wouldn't count on that. This also depends on your optimization settings... ;) There's a compiler switch that tells the compiler to expand "any suitable" function as inline, which would generate the same code as if you would have referenced the variable directly even though you haven't declared the function explicitly as inline. Then you would be back to square one, with the possibility that the variable could be optimized into a register.

"It's supposed to be hard, otherwise anybody could do it!" - selfquote
"High speed never compensates for wrong direction!" - unknown

[Eugen Podsypalnikov]

Yes, saved... :) Thank you - for the both explanations, Roger !

virtual void BeHappy() = 0;

[David Crow]

Eugen Podsypalnikov wrote:

DWORD WINAPI CYourDialog::ThreadProc(CYourDialog* pcDlg)

Shouldn't this be:

UINT CYourDialog::ThreadProc( LPVOID pcDlg )

"One man's wage rise is another man's price increase." - Harold Wilson

"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons

"Man who follows car will be exhausted." - Confucius

[Eugen Podsypalnikov]

Yes, of course :) You could use my declaration too and pass it by the casting (AFX_THREADPROC) , so you can use its parameter pcDlg without casting... :)

virtual void BeHappy() = 0;

[kartikthakre]

Thanks for reply, But i already written that it is working for static and global function. What i want is that it is work for member function. I am waiting for reply thanks

[kartikthakre]

MyThreadProc is not a static function, it is simple member function.

[David Crow]

Which means it cannot be used an argument to AfxBeginThread().

"One man's wage rise is another man's price increase." - Harold Wilson

"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons

"Man who follows car will be exhausted." - Confucius

[David Crow]

kartikthakre wrote:

What i want is that it is work for member function.

You can't do it directly. What you'll have to do is:

void CMyDlg::ThreadProc( void )
{
...
}

UINT ThreadProc( LPVOID lpParam )
{
CMyDlg *pDlg = (CMyDlg *) lpParam;

pDlg->ThreadProc();

return 0;

}

static UINT CMyDlg::ThreadProc( LPVOID lpParam )
{
CMyDlg *pDlg = (CMyDlg *) lpParam;

pDlg->ThreadProc();

return 0;

}

AfxBeginThread(ThreadProc, this); // static member
AfxBeginThread(::ThreadProc, this); // global

"One man's wage rise is another man's price increase." - Harold Wilson

"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons

"Man who follows car will be exhausted." - Confucius

[kartikthakre]

but what is the region, so that member function pointer is not pass to AfxBeginThread.