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From: mneerach@iiic.ethz.ch (Matthias Ulrich Neeracher)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Can I count on any alignment from NewHandle or NewPtr?
Message-ID: <27360@neptune.inf.ethz.ch>
Date: 11 Mar 91 09:40:02 GMT
References: <3588@ux.acs.umn.edu>
Sender: news@neptune.inf.ethz.ch
Reply-To: mneerach@iiic.ethz.ch
Organization: Departement Informatik, ETH, Zurich
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In article <3588@ux.acs.umn.edu>, dhoyt@vx.acs.umn.edu (DAVID HOYT) writes:
>'''
>  Can I count on any sort of alignment from the mac memory manager?  Or do I
>have to roll my own by allocating n-1 more bytes than I really need?
>  Also, is there any guarentee on stack alignment?  I'm trying to build a
>garbage collector for MacApp/C++ and it would be faster if I could rely on
>alignment.

You can count on word alignment, but not longword alignment both for heap
blocks and stack values. There are certain compilers which try to keep
the stack always longword aligned - one of them is described in a paper by
Michael Franz in a recent issue of SIGPLAN Notices. It *might be* that on
newer machines, heap blocks are longword aligned, but I know from painful
experience that at least on a Plus, this is not always true.

Matthias

-- 
Matthias Neeracher                                   mneerach@iiic.ethz.ch
   "These days, though, you have to be pretty technical before you can 
    even aspire to crudeness." -- William Gibson, _Johnny Mnemonic_