Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!think.com!zaphod.mps.ohio-state.edu!swrinde!cs.utexas.edu!uwm.edu!lll-winken!sun-barr!apple!netcomsv!sjsumcs!horstman
From: horstman@mathcs.sjsu.edu (Cay Horstmann)
Newsgroups: comp.lang.c++
Subject: Re: Initializing Global Objects
Message-ID: <1991May27.060310.16757@mathcs.sjsu.edu>
Date: 27 May 91 06:03:10 GMT
References: <76813@brunix.UUCP>
Organization: San Jose State University - Math/CS Dept.
Lines: 44

In article <76813@brunix.UUCP> sdm@cs.brown.edu (Scott Meyers) writes:
>
>My question concerns the static class variable that is used to determine
>whether X has already been initialized.  From the ARM:
>
>    class nifty_counter {
>      static count;
>    public:
>      nifty_counter()
>      {
>        if (count++ == 0)
>          // initialize global objects (i.e., X)
>      }
>    };
>
>We know that nifty_counter::count is preinitialized to 0 because it is
>static, but the rules of the language also require that it be initialized
>by the programmer somewhere.  My question is this:  to what value should it
>be initialized?  

To zero:
	int nifty_counter::count = 0;
(The =0 is optional.)

>
>Prior to this statement is the declaration of the static nifty_counter
>object, so we know that the nifty_counter constructor will have been called
>by the time that nifty_counter::count is explicitly initialized.  As a
>result, at the time when nifty_counter::count is initialized, it's value
>will no longer be 0, since it will have been incremented inside the
>constructor.  If its value is reset to 0 (the explicit initialization
>value), then if a different nifty_counter object is subsequently
>initialized (possible, since it could be from a different translation
>unit), won't X be initialized *again*?
>

I think you have the wrong conception of the initialization of static
integers. They are just set to 0 in the load image, so it is guaranteed
that they are zero before any constructors of static objects are executed.
(That is why in C this stuff was never an issue--all initial values
of statics were precomputed by the loader.) There is no code explicitly 
setting nifty_counter::count to 0. 

Cay