From: utzoo!decvax!decwrl!sun!megatest!fortune!hpda!hplabs!hao!seismo!rlgvax!guy
Newsgroups: net.unix-wizards
Title: Re: Questions about nil-pointer dereferences (the "plague")
Article-I.D.: rlgvax.174
Posted: Thu Mar 31 11:58:12 1983
Received: Sun Apr  3 04:04:10 1983
References: sri-arpa.746

I thought VMS mapped page 0 out of your address space, precisely to prohibit
dereferencing null pointers?  UNIX on our (i.e., CCI's) Power/5 68000 machine
puts the kernel in the low half of your address space, and read/write protects
it, so you can't dereference a null pointer there; I agree 1000% with this.
Code should not dereference NULL pointers.  Period.  In fact, it wouldn't be
too hard to add a new executable image type to UNIX (at least on machines
where throwing away page 0 wouldn't be too expensive, such as VAXes) where
the text begins at 1024 (which, I believe, the linker can do already) and
page 0 is read/write/execute protected.  That way, you can catch bad code
which tries to dereference null pointers.

					Guy Harris
					RLG Corporation
					{seismo,mcnc,we13}!rlgvax!guy