Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!seismo!lll-crg!hoptoad!gnu
From: gnu@hoptoad.uucp (John Gilmore)
Newsgroups: net.micro.amiga
Subject: Re: making reentrant code for "resident" programs
Message-ID: <969@hoptoad.uucp>
Date: Tue, 12-Aug-86 04:32:01 EDT
Article-I.D.: hoptoad.969
Posted: Tue Aug 12 04:32:01 1986
Date-Received: Tue, 12-Aug-86 23:32:44 EDT
References: <661@usc-oberon.UUCP> <1468@amiga.amiga.UUCP> <870@tekigm.UUCP> <1478@amiga.amiga.UUCP>
Organization: Nebula Consultants in San Francisco
Lines: 20

In article <1478@amiga.amiga.UUCP>, jimm@amiga.UUCP (James D. Mackraz) writes:
> 2) Perhaps the Lattice C Compiler can create re-entrant code.

There is no way an average C program can get by without using global
variables (eg errno, the standard-I/O file tables, etc).  This means
that a facility to let programs be "reentrant", which does not provide
for separate data areas for each copy of the running, is foolhardy in a
portable C language environment.

(It's not clear that this is specific to C.  Know any programs that
have NO global variables and NO local static variables?)

A properly written compiler can support reentrancy -- even in a system
without memory management -- by making global data references relative
to an address register (rather than using the slow, cumbersome absolute
addressing mode most compilers use).  I don't know of any that do this,
however, since there are complications involved.
-- 
John Gilmore  {sun,ptsfa,lll-crg,ihnp4}!hoptoad!gnu   jgilmore@lll-crg.arpa
		     May the Source be with you!