Path: utzoo!attcan!uunet!wyse!mips!mash
From: mash@mips.COM (John Mashey)
Newsgroups: comp.sys.m68k
Subject: Re: quad-aligning the 68020 stack
Keywords: 68020 stack longword alignment quad
Message-ID: <2727@winchester.mips.COM>
Date: 7 Aug 88 01:28:57 GMT
References: <2194@uhccux.uhcc.hawaii.edu> <4431@cbmvax.UUCP>
Reply-To: mash@winchester.UUCP (John Mashey)
Organization: MIPS Computer Systems, Sunnyvale, CA
Lines: 20

In article <4431@cbmvax.UUCP> ditto@cbmvax.UUCP (Mike "Ford" Ditto) writes:
....
>For real 32-bit 68020 systems, I am a firm believer in keeping all
>stacks and structures longword aligned at all times.  This means the
>C compiler should promote all function arguments to a multiple of 32
>bits and pad structures so that longword elements are at aligned
>offsets.  Malloc() and similar functions should return longword aligned
>storage....

Right philosophy, but consider thinking further ahead to 64-bit objects,
at least.  Structures should be aligned to doublewords, especially,
or you may later run into the same problem that 68K compilers did,
if they started aligning longwords on 16-bit boundaries, and then had
incompatible structures when shifting to 68020-preferred alginment,
or to RISC machines that really want objects aligned properly.
-- 
-john mashey	DISCLAIMER: <generic disclaimer, I speak for me only, etc>
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