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From: cwr@pnet01.cts.com (Will Rose)
Newsgroups: comp.os.minix
Subject: NULL macro
Message-ID: <710@crash.cts.com>
Date: 15 Nov 89 07:36:06 GMT
Sender: root@crash.cts.com
Organization: People-Net [pnet01], El Cajon CA
Lines: 27

Rex Jaesche, who was (is?) a member of the ANSI C standards committe,
discussed this macro extensively in the Sep/Oct 88 C Users Journal.  His
summary was that ANSI C (in which we *believe*, right?) had three possible
definitions for the NULL pointer constant:

     #define NULL 0
     #define NULL 0L
     #define NULL (void *)0

Most MSDOS C compilers (he goes on to say) conditionally compile NULL into one
of the first two definitions; the third case should work in all
ANSI-conforming programs, but there are plenty of cases where it won't work in
non-ANSI code.

To understand why, read his (six page) article.

Will
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