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From: Leisner.Henr@Xerox.COM (Marty)
Newsgroups: comp.lang.c
Subject: NULL function pointers
Message-ID: <9268@brl-adm.ARPA>
Date: Mon, 14-Sep-87 10:58:22 EDT
Article-I.D.: brl-adm.9268
Posted: Mon Sep 14 10:58:22 1987
Date-Received: Tue, 15-Sep-87 04:52:31 EDT
Sender: news@brl-adm.ARPA
Lines: 20

K&R guarantees pointers to valid data objects are non-NULL.  But what
about function pointers?  I found no reference to guarantees to non-NULL
function pointers and a number of compiler system/linkers I've seen have
no problem inserting C functions at address 0.

It seems like a good idea not to have  a valid function at address NULL so it
is easy to test a function pointer for validity.

On MS-Dos, for instance, a signal handler at the top of your program
(address 0) will often cause problems for signal() (at least with aztec
C).



marty
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