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Message-ID: <3BE90C31.E677AA07@syntrex.com>
Date: Wed, 07 Nov 2001 11:25:53 +0100
From: Pavel Tsekov <ptsekov AT syntrex DOT com>
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To: "J. J. Farrell" <jjf AT bcs DOT org DOT uk>
CC: cygwin AT cygwin DOT com
Subject: Re: Global variables - was: Re: [PATCH proposal] Re: Setup use on win2k 
 - a me too ...
References: <004201c1675a$261ae960$38810142 AT pavilion>
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"J. J. Farrell" wrote:
> 
> Larry Hall wrote:
> > At 12:06 PM 11/6/2001, Pavel Tsekov wrote:
> > >Christopher Faylor wrote:
> > > >
> > > > It is not a bad habit to rely on global variables being 0.  If they
> > > > aren't then something is seriously wrong with either 'ld' or the
> > > > run-time the loader.
> > >
> > > I didn't know this actually, so I thought it may the cause for the
> > > problem. ... However the MSVC compiled programs do not have globals,
> > > except the static ones, initialized to zero ...
> >
> > Chris' statement about zeroing out globals is important in it's
> > scope but shouldn't be taken too far.  Obviously, to be portable,
> > adding the explicit initialization to 0 is important.  Although gcc/ld
> > may not require this, other compiler suites may (as you pointed out) and
> > code, in general, can't assume too much about the compiler being used.
> > ...
> > I just wanted to make this point so that someone
> > doesn't get the wrong impression about initializing globals to 0.  And
> > no apologies are necessary for not knowing about an obscure optimization
> > feature of a compiler suite. :-)
> 
> In C, global variables which are not explicitly initialized MUST
> be initialized as if their definition includes an assignment of
> an integer constant 0. This is not an obscure feature of some
> compilers, it's a fundamental feature of the C language! Any
> system which doesn't do this is not a conforming C environment.
> Assuming that an uninitialized global variable will behave as if
> its definition includes '=0' is entirely portable.
> 
> I don't know C++, so I can't be sure it's the same. I thought I
> knew of most of the situations where a conforming C program will
> behave differently when compiled with a C++ compiler, and the
> ones I know of are more subtle than this. I'll be amazed if C++
> differs from C on such a basic point - but I'm easily amazed.
> 
> Pavel, can you provide an example of where MSVC doesn't do this
> (perhaps to me privately rather than the list). I've never
> experienced this bug, but I've only used MSVC for kernel-mode
> development where different things may come into play.

I did a total mess - I've refreshed my memory last night after
Cristopher
posted his message about globals initialization and I've found that all
I wrote about the MSVC is wrong too. So this post of mine should be
totally
ignored.

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