RE: Pointer to a function forbid!!

["Glover George" <dime@gulfsales.com>]

Thank you, but could you explain something to me ?  Is f the name of the
function I'm needing a pointer to, or is it ADDED to the class?  I'm not
quite sure how I use this.  Is m() the member function that I'm needing
the pointer to? I know I replace the A with the name of my class, but
I'm not sure which other items I'm supposed to substitute for.  Thanks a
lot man.




> -----Original Message-----
> From: sebastian-huber@web.de [mailto:sebastian-huber@web.de] 
> Sent: Friday, April 12, 2002 11:59 AM
> To: Glover George
> Subject: Re: Pointer to a function forbid!!
> 
> 
> Hello,
> if you want to avoid global variables, you can try this:
> 
> class A {
> public:
> 	static void f( void* thisPointer)
> 	{
> 		static_cast<A*>( thisPointer)->m();
> 	}
> 
> private:
> 	void m();
> };
> 
> This works a least with the POSIX thread functions.
> 
> On Thursday 11 April 2002 21:32, you wrote:
> > That's fine, I really just didn't know if I could attach 
> code on the 
> > list. Here's where I'm passing the address of 
> > gate.DeviceCallbakEventHandler() to a function (which is 
> part of the 
> > Intel UPnP SDK, I'll put it's declaration below).  See, I have some 
> > code that this works with, but its pure C.  The funtions 
> were defined 
> > before main (I mean at the top of the file that contains 
> main).  They 
> > didn't use the & before the function (which was just 
> > DeviceCallbackEventHandler), but if I don't include the &, 
> it says it 
> > can't find a matching function for int (*) (<paramaters>). 
> Candidates 
> > are int DeviceCallbackEventHandler(<parameters>).
> >
> > I know there can be pointers to functions, but I'm not 
> understanding 
> > why it won't work here.
> >
> > Muchas Gracias in advance!!!
> >
> > Int main (arc, argv**){
> > Gate gate;
> > .
> > .
> > .
> > if ((ret = UpnpRegisterRootDevice(desc_doc_url,
> > &gate.DeviceCallbackEventHandler,
> >                                 &gate.device_handle,
> > &gate.device_handle)) != UPNP_E_SUCCESS)
> >         {
> > 		...(SNIP)
> >         }
> > .
> > .
> > .
> > }
> > ///////Here is the class declaration for a Gate class.
> >
> > class Gate
> > {
> >         public:
> >                 Gate();
> >                 ~Gate();
> >
> >                 int DeviceStateTableInit(char *);
> >                 int DeviceHandleSubscriptionRequest (struct 
> > Upnp_Subscription_Request *sr_event);
> >                 int DeviceHandleGetVarRequest(struct 
> > Upnp_State_Var_Request *);
> >                 int DeviceHandleActionRequest(struct 
> > Upnp_Action_Request *);
> >                 int DeviceCallbackEventHandler(Upnp_EventType 
> > EventType, void*, void*);
> >
> >                 PortMapList m_list;
> >                 IPCon *m_ipcon;
> >                 char *gate_udn;
> >                 UpnpDevice_Handle device_handle;
> > };
> > ///////AND THE following is the declaration provide in the 
> Intel UPnP 
> > SDK for Linux
> >
> >
> > /** {\bf UpnpRegisterRootDevice} registers a device application with
> >  *  the UPnP API.  A device application cannot make any other API
> >  *  calls until it registers using this function.  Device 
> applications
> >  *  can also register as control points (see {\bf 
> UpnpRegisterClient}
> >  *  to get a control point handle to perform control point
> >  *  functionality).
> >  *
> >  *  {\bf UpnpRegisterRootDevice} is synchronous and does 
> not generate
> >  *  any callbacks.  Callbacks can occur as soon as this function 
> > returns.
> >  *
> >  *  @return An integer representing one of the following:
> >  *    \begin{itemize}
> >  *      \item {\tt UPNP_E_SUCCESS}: The operation completed
> > successfully.
> >  *      \item {\tt UPNP_E_FINISH}: The UPnP library is already
> > terminated or
> >  *                                 is not initialized.
> >  *      \item {\tt UPNP_E_INVALID_DESC}: The description 
> document was
> > not
> >  *              found or it does not contain a valid device 
> description.
> >  *      \item {\tt UPNP_E_INVALID_PARAM}: Either {\bf 
> Callback} or {\bf
> > Hnd}
> >  *              are not valid pointers or {\bf DescURL} is 
> {\tt NULL}.
> >  *      \item {\tt UPNP_E_NETWORK_ERROR}: A network error occurred.
> >  *      \item {\tt UPNP_E_SOCKET_WRITE}: An error or 
> timeout occurred
> > writing
> >  *              to a socket.
> >  *      \item {\tt UPNP_E_SOCKET_READ}: An error or timeout occurred
> > reading
> >  *              from a socket.
> >  *      \item {\tt UPNP_E_SOCKET_BIND}: An error occurred binding a
> > socket.
> >  *      \item {\tt UPNP_E_SOCKET_CONNECT}: An error 
> occurred connecting
> > the
> >  *              socket.
> >  *      \item {\tt UPNP_E_OUTOF_SOCKET}: Too many sockets 
> are currently
> >  *              allocated.
> >  *      \item {\tt UPNP_E_OUTOF_MEMORY}: There are insufficient
> > resources to
> >  *              register this root device.
> >  *    \end{itemize} */
> >
> > int UpnpRegisterRootDevice(
> >     IN const char *DescUrl,    /** Pointer to a string 
> containing the
> >                                    description URL for this 
> root device
> >                                    instance. */
> >     IN Upnp_FunPtr Callback,   /** Pointer to the callback 
> function for
> >                                    receiving asynchronous events. */
> >     IN const void *Cookie,     /** Pointer to user data 
> returned with
> > the
> >                                    callback function when 
> invoked. */
> >     OUT UpnpDevice_Handle *Hnd /** Pointer to a variable to 
> store the
> >                                    new device handle. */
> >     );
> >
> > > -----Original Message-----
> > > From: sebastian-huber@web.de [mailto:sebastian-huber@web.de]
> > > Sent: Thursday, April 11, 2002 1:42 PM
> > > To: Glover George
> > > Subject: Re: Pointer to a function forbid!!
> > >
> > >
> > > Hello,
> > > a bit of code might be helpful.
> > >
> > > On Thursday 11 April 2002 20:31, you wrote:
> > > > Hi, I was wondering if there is ANYWAY to overcome this
> > >
> > > error message
> > >
> > > > with G++;
> > > >
> > > > I have to pass a pointer to a function as a parameter to some 
> > > > other function.  However, the funtion I need to pass is a member
> > >
> > > function of
> > >
> > > > a class.  When I do, g++ complains with this.
> > > >
> > > > ISO C++ forbids taking the address of a bound member
> > >
> > > function to form
> > >
> > > > a pointer to member function.  Cannont convert ..... (snip)
> > > >
> > > > What exactly does this mean and why not?  The function is
> > >
> > > of an object
> > >
> > > > that has been initialized.  It is local to main however.
> > >
> > > Is it that
> > >
> > > > it needs to be created with a new before I can do it or is
> > >
> > > there just
> > >
> > > > absolutely no way to pass a pointer to a member function?
> > > >
> > > > Thank you.
> > > >
> > > > Glover George
> > > > Systems/Networks Admin
> > > > Gulf Sales & Supply, Inc.
> > > > (228) 762-0268
> > > > dime@gulfsales.com
> > > > http://www.gulfsales.com
>