Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!attctc!chasm
From: chasm@attctc.Dallas.TX.US (Charles Marslett)
Newsgroups: comp.lang.c
Subject: Re: effect of free()
Summary: Reprise -- register varibles
Message-ID: <9279@attctc.Dallas.TX.US>
Date: 9 Sep 89 03:04:57 GMT
References: <319@cubmol.BIO.COLUMBIA.EDU> <3756@buengc.BU.EDU> <14636@bfmny0.UU.NET>
Organization: The Unix(R) Connection, Dallas, Texas
Lines: 24



Now that we have seen code that can really generate a trap on (most) invalid
segments, and could have been generated by a (very bad) compiler, another
point has been raised: what about register variables?

If Chris Torek's pointer, passed to free(), were a register variable, and
presumably saved on the stack when the system routine free() was called,
it will be reloaded when the calling routine is resumed.  This would be a
VERY-BAD-THING!  And probably non-standard.

I think the probability of a standard-conforming compiler generating a trap
here, and not generating a trap under all legal conditions, is approaching
NULL ;^).

Of course, segment registers need not be used to hold register pointers,
but it makes more sense than using them as paths to the ALU.

Charles
===========================================================================
Charles Marslett
STB Systems, Inc.  <== Apply all standard disclaimers
Wordmark Systems   <== No disclaimers required -- that's just me
chasm@attctc.dallas.tx.us