Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!henry
From: henry@utzoo.UUCP (Henry Spencer)
Newsgroups: net.lang
Subject: Re: Self-modifying code
Message-ID: <3434@utzoo.UUCP>
Date: Fri, 30-Dec-83 16:18:38 EST
Article-I.D.: utzoo.3434
Posted: Fri Dec 30 16:18:38 1983
Date-Received: Fri, 30-Dec-83 16:18:38 EST
References: <1096@mit-eddie.UUCP>, <319@decvax.UUCP>
Organization: U of Toronto Zoology
Lines: 14

One should distinguish between real self-modifying code and doing
compilation at "run time".  In the latter case, the code is not really
modifying itself:  new code (not modified old code) is being created
and then run.  This is a useful technique that is not used as much as
it should be, although admittedly it's not a trivial thing to do and
it obviously has severe portability problems.

Another example of this sort of thing is that the RasterOp implementation
for the Blit compiles optimal code for each request rather than trying
to build in all the special cases ahead of time.  The compilation takes
something like 600 us worst case, so the overhead involved is small.
-- 
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,linus,decvax}!utzoo!henry