Path: utzoo!mnetor!uunet!mcvax!ukc!its63b!aiva!richard
From: richard@aiva.ed.ac.uk (Richard Tobin)
Newsgroups: comp.unix.questions
Subject: Re: regcmp()
Message-ID: <262@aiva.ed.ac.uk>
Date: 22 Feb 88 22:04:41 GMT
References: <9@vsi.UUCP> <15100006@bucc2>
Reply-To: richard@uk.ac.ed.aiva (Richard Tobin)
Organization: Bannerman's Bar, Cowgate, Edinburgh
Lines: 22

In article <15100006@bucc2> brian@bucc2.UUCP writes:
>> Not if you cast it to "char *", it isn't!  Passing "(char *)0" is quite
>> sufficient, unless the compiler is horribly broken.
>  Tsk, tsk, tsk. This statment is true if sizeof(int) == sizeof(pointer).

It certainly is.  It's also true if sizeof(int) != sizeof(pointer).

The way you get a null character pointer is by casting 0 to (char *).
If a compiler doesn't take (char *)0 to be a null character pointer,
it's broken, regardless of the length of pointers.  That's just the way
it is.

Casting 0 to (char *) is *NOT* defined to pretend that zero bit-pattern is
a pointer, it's defined to to *convert* 0.  The resulting bit pattern can
be anything at all (it's often zero).  All that matters is that it's
always the same, and that no object has it as its address.

-- Richard
-- 
Richard Tobin,                         JANET: R.Tobin@uk.ac.ed             
AI Applications Institute,             ARPA:  R.Tobin%uk.ac.ed@nss.cs.ucl.ac.uk
Edinburgh University.                  UUCP:  ...!ukc!ed.ac.uk!R.Tobin