Re: replicating default constructor's "non-initializing state"

From:
"Victor Bazarov" <v.Abazarov@comAcast.net>
Newsgroups:
comp.lang.c++,microsoft.public.vc.language
Date:
Mon, 7 Apr 2008 15:19:10 -0400
Message-ID:
<ftds3e$nmv$1@news.datemas.de>
Jason Doucette wrote:

Situation:
I have a simple struct that, say, holds a color (R, G, and B). I
created my own constructors to ease its creation. As a result, I lose
the default constructor. I dislike this, but it's easy to solve: I
just make my own default constructor.

Problem:
My own default constructor is considered to be *initializing the
variable* (even though it doesn't), whereas the original one does
not. Thus, when I declare and use it before initializing it, the
compiler no longer warns me.


That's your choice, isn't it? You've chosen to implement your c-tor
(which is supposed to initialise the members) in such a way that does
*not* do what it promises to do. So, why are you complaining? It is
not a problem, or at least it's very easy to solve, isn't it?

Question:
Are there any compiler settings (even compiler specific ones; I am
using MSVC++) that state MY default constructor behaves exactly like
the regular default constructor?


Not that I know of.

Thanks for your time,
Jason

P.S. My default constructor could initialize the variable to all 0's,
but this has two unwanted effects: 1. It slows down code in which
this initialization needn't occur.


Can you share the numbers, how much *does* it actually "slow down
the code"?

2. It potentially hides bugs that
would show up if it were left uninitialized as it should be.


Written *correctly* it _prevents_ bugs, not hides them.

 (This is
similar to how MSVC++'s debugger initializes all variables to 0, which
is silly, since it should initialize them to randomness -- as will
happen in the release build -- to make bugs appear as quickly as
possible).


Not similar at all. When in the "debug" build variables are given
some values whereas in the "non-debug" they are not, you have a very
big problem if your code ever depends on this. When your default
c-tor initialises member variables (to 0 or whatever) *always*, there
is no randomness, and you can *rely* on the initialisation happening.

V
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