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From: ingoldsby@calgary.UUCP (Terry Ingoldsby)
Newsgroups: net.micro.amiga
Subject: Re: making reentrant code for "resident" programs
Message-ID: <310@vaxb.calgary.UUCP>
Date: Wed, 13-Aug-86 14:38:38 EDT
Article-I.D.: vaxb.310
Posted: Wed Aug 13 14:38:38 1986
Date-Received: Thu, 14-Aug-86 20:45:22 EDT
References: <661@usc-oberon.UUCP> <1468@amiga.amiga.UUCP> <870@tekigm.UUCP> <969@hoptoad.uucp>
Organization: U. of Calgary, Calgary, Ab.
Lines: 25
Summary: Re-entrant `C' Code

In article <969@hoptoad.uucp>, gnu@hoptoad.UUCP writes:
> 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!


If I'm not mistaken, the `C' Compilers written for the OS9 operating system
do generate re-entrant code in the manner described by John Gilmore.