CreateThread problem... 1

[mattKnight]

Hi all,

First post in this forum, so pls forgive a newbie...
Background
OS Winnt sp6
Dev Platfom MSVC++ v6 SP5

I recently started "playing" with multi-threading (oh joy)
however I have a problem with CreateThread...

void CScheduler::Watcher()
{
int x = 5;  // arbitary parameter fr new thread
// Start new thread hThread and dwThreadID2 declared as
// class member variables

hThread = CreateThread(NULL,0,
          (LPTHREAD_START_ROUTINE)ThreadStart,
           (LPVOID)x, 0, &dwThreadID2);
// To do
// useful work and cleanup code (using thread 1)
}
DWORD WINAPI CScheduler::ThreadStart(LPVOID Arg)
{
// to do 
// some other useful work
//clean up code
}

This code is inside simple ATL object (set I think for free thread)
however, It doesn't compile - I get error C2440 at the CreateThread line
the error text reads

'type cast': cannot convert from '' to 'unsigned long )__stdcall *)(void *)'

None of the functions with this name in scope match the target type

I think that this is a scope issue with "ThreadStart", but where should it be (class, global etc)?

All help will be gratefully received

Thanks

Matt

 

[Temps]

Matt,

If you want to pass a pointer to a member function of a class, the member function must be declared as 'static' (the problem is that there is a hidden 'this' pointer for every non-static member function).

Within the header file declare

public:

static DWORD WINAPI CScheduler::ThreadStart (LPVOID lparam);

and within the code


hThread = CreateThread(NULL,0, CScheduler::ThreadStart,
(LPVOID)x, 0, &dwThreadID2);


Hope this helps.

Temps

 

[mattKnight]

Temps,

That's it! problem solved

There will be other problems, I am sure!
Thanks again

Matt

 

[mattKnight]

Coupla other quick questions...

should "threadStart" be private or public?
nothing other than private makes much sense to me!
and
What sort of cast should be used other than type cast (old style?)
i.e. should I replace

(LPTHREAD_START_ROUTINE)CScheduler::ThreadStart

with

reinterpret_cast<THREAD_START_ROUTINE>(CScheduler::Threadstart)

or
static_cast<> etc?

My understanding would be reinterpret_cast as I am trying to cast a funtion pointer void(?) to a typed function pointer.

Is that correct?

Matt

 

[Temps]

private makes sense.

You don't need to cast - the 'signature' of the static member function already matches what CreateThread is expecting.

Temps

 

[mattKnight]

Thanks again

Matt

 

[KeavDog]

Just a suggestion: I would use _beginthreadx rather than CreateThread as CreateThread can lead to sync problems if you are calling any standard c lib rtl functions.

Thanks,
John