Path: utzoo!attcan!uunet!aplcen!samsung!cs.utexas.edu!mailrus!ncar!boulder!stan!dancer!imp
From: imp@dancer.Solbourne.COM (Warner Losh)
Newsgroups: comp.lang.c++,apple.general
Subject: Re: Failed allocation in constructors?
Message-ID: <1990Jul11.180345.21464@Solbourne.COM>
Date: 11 Jul 90 18:03:45 GMT
References: <9075@goofy.Apple.COM> <42825@apple.Apple.COM>
Sender: news@Solbourne.COM
Organization: Solbourne Computer, Inc.
Lines: 19

In article <42825@apple.Apple.COM> fair@Apple.COM (Erik E. Fair) writes:
>So, dereferencing zero isn't a bad thing; it's just bad to assume that
>you always can across all possible hardware architectures that your
>program might be run on.

Dereferencing "zero" is a bad thing.  "0" is the Nil pointer in C and
C++.  It is defined to point to an address that doesn't exist (or is
at least unique).  So if you dereference it, you are asking for
trouble.

In most implementations of C and C++ a Nil pointer has all its bits
turned off, but not all implementations do this.  Regardless of the
implementation, saying "p=0" will get you a Nil pointer.  So if you
then say *p, that is an error.  However, according to the standard,
compilers are free to not notify the user this error has occurred.

-- 
Warner Losh		imp@Solbourne.COM
All the world is not a VAX. :-)