🚀 go-pugleaf

"Mike Collins" <its@TheBottomOfThePost> wrote:

>extern TInjectController *InjectController;

Declaration.

>// implimentation
>void CALLBACK TInjectController::IPCProcessMsg(char *cName, void *pMsgBuf, 
>unsigned int iMsgLen,
>                                               void *pRtnBuf, unsigned int 
>iRtnLen)
>{
>   InjectController->csIPCCallBack->Enter();
>   ...
>   InjectController->csIPCCallBack->Leave();
>}

Use.

>- I've declared the callback function as static and stuck in the extern 
>reference at the bottom of the class.  I did this because it's the only way 
>that i found that works in the past, with other callbacks i.e. EnumWindows 
>etc...
>
>However, on compile i get "[Linker Error] Unresolved external 
>'_InjectController' referenced from C:\DOCUMENTS AND 
>SETTINGS\ADMINISTRATOR\DESKTOP\TEST 
>INJECTOR\TINJECTCONTROLLER\TINJECTCONTROLLER.OBJ"

Complaint about lack of definition. 

You're trying to call methods of an object that doesn't exist anywhere
in your source code. You told the compiler that it would exist in some
source file somewhere, but you don't seem to have actually declared it
anywhere.

>If i remove the reference to the wrapper from within the callback, it works 
>fine - but defeats the object and breaks my design.

Well, yes.

>Can anyone help me out here?  Also, can anyone tell me why the extern 
>reference seems to be necessary >

It's not necessary at all. But if you declare it *in the header* without
an extern, then it's a definition as well as a declaration, and it will
exist in every single source file that uses that header.

Do you initialise the pointer either?

Alan Bellingham
-- 
Team Browns
ACCU Conference 2008: 2-5 April 2008 - Oxford (probably), UK

Apologies for the last bit regarding the extern - obviously tells the 
compiler that there is a object of that type floating around some where..

But as for the rest, i'm still flummoxed...

"Mike Collins" <its@TheBottomOfThePost> wrote in message 
news:46716c33@newsgroups.borland.com...
> Hi all, been having a right nightmare with a callback 

I see what you are saying Alan.  however, in my main form, I have a pointer 
declared to this object, in the forms public section.  I assumed that this 
would be enough based on the extern i.e. indicates that there is a an object 
of this type somewhere.  I've tried including the Main.h in the wrapper 
class but I get some kind of circular reference compile error.

The only thing that appears to fix it is if i declare TInjectController 
*InjectController at the start of the TInjectController implementation - 
before the constructor.  Is this valid ?  Is there any issues with this? 
Can you suggest a better approach?

Thanks again,

Mike



"Alan Bellingham" <alan@lspace.org> wrote in message 
news:agr2731rl90vspqaucjmhlk7e2al16e028@4ax.com...
> "Mike Collins" <its@TheBottomOfThePost> wrote:
>
>>extern TInjectController *InjectController;
>
> Declaration.
>
>>// implimentation
>>void CALLBACK TInjectController::IPCProcessMsg(char *cName, void *pMsgBuf,
>>unsigned int iMsgLen,
>>                                               void *pRtnBuf, unsigned int

"Mike Collins" <its@TheBottomOfThePost> wrote:
>
> [...] I did this because it's the only way that i found that
> works in the past, with other callbacks i.e. EnumWindows 
> etc...

This has worked for me:

    protected:
        static  bool __stdcall EnumWindowsCallBack( HWND hWnd, LPARAM lParam );

//-------------------------------------------------------------
TSingleInstance *ThisSingleInstance = NULL;
//-------------------------------------------------------------
__fastcall TSingleInstance::TSingleInstance(TComponent* Owner) : TComponent(Owner)
{
    .....
    ThisSingleInstance = this;
    .....
}
//-------------------------------------------------------------
__fastcall TSingleInstance::~TSingleInstance()
{
    .....
    ThisSingleInstance = NULL;
}
//-------------------------------------------------------------
bool __stdcall TSingleInstance::EnumWindowsCallBack( HWND hWnd, LPARAM lParam )
{
    char WindowClassName[256] = { 0 };
    if( ::GetClassName(hWnd, WindowClassName, 255) )
      {
          if( stricmp(WindowClassName, reinterpret_cast<char*>(lParam)) == 0 )
            {
                if( hWnd != ThisSingleInstance->FParentForm->Handle )
                  {
                      ThisSingleInstance->hFirstInstance = hWnd;
                      return FALSE;
                  }
            }
      }
    return TRUE;
}
//-------------------------------------------------------------

Note the use of ThisSingleInstance in the CallBack.

~ JD

Cheers JD, think the problem was that i was creating the callback in a pure 
class and my pointer to it was in a TForm that created the class - all 
working now though


"JD" <nospam@nospam.com> wrote in message 
news:46719667@newsgroups.borland.com...