Path: utzoo!attcan!uunet!husc6!bbn!mit-eddie!rutgers!mcnc!rti!xyzzy!meissner
From: meissner@xyzzy.UUCP (Usenet Administration)
Newsgroups: comp.lang.c
Subject: Re: retiring gets(3)
Message-ID: <1977@xyzzy.UUCP>
Date: 22 Nov 88 01:24:11 GMT
References: <1988Nov8.054845.23998@utstat.uucp> <7963@bloom-beacon.MIT.EDU> <4509@aldebaran.UUCP>
Reply-To: meissner@xyzzy.UUCP (Michael Meissner)
Organization: Data General (Languages @ Research Triangle Park, NC.)
Lines: 26

In article <4509@aldebaran.UUCP> jimp@cognos.UUCP (Jim Patterson) writes:
	/* stuff deleted */
| I know of at least one system where the system convention is not 0;
| Data General MV systems have instructions which take -1 as the null
| pointer value, and this has persisted through many system call
| conventions as well. However, the C implementation still considers a
| null pointer to be 0 even though this requires quite a bit of "glue"
| around some system calls to interface between the two formats.
| Requiring that the "null pointer constant" be 0, as ANSI C does, just
| makes any other implementation painfully difficult (and is begging for
| problems when porting software as well).

Sigh....  Yes the MV does have some queue instructions that take -1
for a null pointer.  However, the general NULL pointer as defined by
the C library is all 0's, as it is for other DG languages.  Whatever
other faults we have (three pointer types, etc.), a non-zero NULL is
not one of them.

And yes there are some system calls that want -1 in pointer fields as
a special value, there are also system calls that want you to do a
logical OR with the high bit set.  Such is life.....

-- 
Michael Meissner, Data General.

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