RE: ? initHookRegister()

["Liyu, Andrei" <liyua@ornl.gov>]

>From Microsoft VC help.
==========
Static
Objects and variables declared as static retain their values for the
duration of the program's execution. In recursive code, a static object
or variable is guaranteed to have the same state in different instances
of a block of code.

Objects and variables defined outside all blocks have static lifetime
and external linkage by default. A global object or variable that is
explicitly declared as static has internal linkage.

Static objects and variables persist for the duration of the program's
execution.
==========

So, pCServer (from server.h) has 
	- static lifetime (without static word!) == you are right
	- global access (as global object)

Thanks, Andrei.


-----Original Message-----
From: Ralph Lange [mailto:Ralph.Lange@bessy.de] 
Sent: Wednesday, January 21, 2004 11:38 AM
To: Liyu, Andrei
Cc: Marty Kraimer; tech-talk@aps.anl.gov
Subject: RE: ? initHookRegister()

>>>>> "Andrei" == Andrei Liyu <Liyu> writes:

  > Thank you very much.
  > I have small question according 2. Why should static object be?
  > I tried in Windows:

  > //Server.h
  > class CServer{
  > 	...
  > };
  > extern CServer * pCServer;

  > //Server.cpp
  > .....
  > CServer oCServer;
  > CServer * pCServer = & oCServer;

  > It works too.

I don't understand your question - if the declaration of oCServer is
file global in Server.cpp, it _is_ a static object.

The reason for using a static object (as you did) is that the compiler /
runtime system makes sure the object is created (and its constructor
called) at init time. This makes sure myHookFunction is registered
before iocInit() runs.

Ralph


  > -----Original Message-----
  > From: Marty Kraimer [mailto:mrk@aps.anl.gov] 
  > Sent: Monday, January 19, 2004 8:50 AM
  > To: Liyu, Andrei
  > Cc: tech-talk@aps.anl.gov
  > Subject: Re: ? initHookRegister()

  > Liyu, Andrei wrote:
  >> Hi,
  >> 
  >> If I like to do some job during IOC initialization I should call
  >> initHookRegister(). But I couldn't understand where (how) can I
call
  >> this function before iocInit()?

  > I can think of three ways.

  > 1) Call your routine from the st.cmd file

  >      Assume you have a function

  >      int initMyHook(void)
  >      {
  >          return(initHookFunction(myHookFunction));
  >      }


  >     the st.cmd file contains
  >     initMyHook
  >     iocInit

  > 2) Use a C++ static object.

  >     class initMyHook {
  >         public:
  >            initMyHook() {initHookFunction(myHookFunction);}
  >     }
  >     static initMyHook initMyHookObj;

  >     The constructor initMyHook will get called for initMyHookObj at
load
  > time.

  > 3) For 3.14.4 or later use the registrar facility

  >     In your xxxInclude.dbd file the following must appear

  >     registrar(myHook)

  >     Your source file contains

  >     static void myHook(void)
  >     {
  >         static int firstTime = 1;
  >         if(!firstTime) return;
  >         firstTime=0;
  >         initHookFunction(myHookFunction);
  >     }
  >     epicsExportRegistrar(myHook);


  > For 3.14.4 and later method 3) is the recommended method.

  >> Can anybody write couple words about IOC deinitialization? Has
  >> Epics similar hook here?
  >> 

  > Sorry but iocCore is currently written to run forever. There is no
  > deinitialization.

  >> Thanks, Andrei.
  >> 



-- 
      __  Ralph Lange                               Ralph.Lange@bessy.de
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