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From: ForthNet@willett.pgh.pa.us (ForthNet articles from GEnie)
Newsgroups: comp.lang.forth
Subject: ANS TC Magnet for Tick, >BODY, ['],etc
Message-ID: <2922.UUL1.3#5129@willett.pgh.pa.us>
Date: 25 Jun 91 02:31:11 GMT
Organization: (n.) to be organized.  But that's not important right now.
Lines: 46

Category 10,  Topic 25
Message 29        Mon Jun 24, 1991
D.RUFFER [Dennis]            at 00:23 EDT
 
Again, I think you all are missing the point.  Since I won't be passing this
stuff back to Elizabeth for a week, I will try to explain it again.

C, can most certainly cause HERE to return an unaligned address and no, it
does not need to be "fixed" and results will be unpredictable if used by an
operator that is expecting an aligned address.  BASIS does not require HERE to
return an aligned address, but since the programmer is in control of the
situation (and actually caused the misalignment), it is his responsiblity to
use ALIGN before he assumes HERE can be used with an operator that requires
alignment. In other words, if you do a C, and then want to do a HERE @, then
you had better do an ALIGN first.

Why is this such a mystery?

Re: rob@innovus.uucp (Rob Sciuk)

 >=> appropriate boundaries.  Further, `ALLOT' and `,' should align
 >=> on CELL boundaries, and `C,' should ensure that the next
 >=> invocation of `HERE', `ALLOT', `,' etc. will utilize a CELL
 >=> boundary appropriate to the processor [mine].

This is _NOT_ what Elizabeth said.  ALLOT and C, do not do anything about
alignment, nor do they assure that the next invocation of HERE will return an
aligned address.  It is up to the programmer to make these assurances, since
he is the one that used the C, or an odd number of bytes in ALLOT.  In fact,
Elizabeth specifically did say that HERE can return an unaligned address if
the programmer does these things.

At FORTH, Inc. we work on aligned systems all the time and it is really not a
problem.  Sure, a nieve programmer can get himself in trouble, by using HERE
improperly, but in practice, this doesn't happen much.  All the defining words
that are garanteed to return aligned addresses, do the alignment before they
make use of HERE. Yes, this does mean that ALIGN gets executed frequently as
you compile your system, but IMHO, it should be written for speed and frequent
use anyways.

   {B-{)>   DaR
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