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From: toppin@melpar.UUCP (Doug Toppin   X2075)
Newsgroups: comp.arch,comp.lang.c
Subject: RISC Machine Data Structure Word Alignment Problems?
Keywords: risc sun
Message-ID: <111@melpar.UUCP>
Date: 19 Jan 90 23:46:21 GMT
Organization: E-Systems, Falls Church, VA
Lines: 28

We are using the SUN 4/260 which is a RISC architecture machine.
We are having trouble with data alignment in our data structures.
We have to communicate with external devices that require data structures
such as the following:
	struct
	{
		long  a;
		short b;
		long  c;
	};
When we compile and link something referencing this structure the
data produced appears to have had each element word boundary aligned
so that what results appears to be as follows:
	struct
	{
		long  a;
		short b;
		short pad; <==== this was inserted by cc to align next thing
		long  c;
	};
This means that we lose the benefit of data abstraction and have
to create our own output without using structures.
We have not been able to find any Sun-4 cc option that eliminates
this problem. We cannot use the 'compile as Sun-3' option.
Please let us know if you know of a built-in way around this.
thanks
Doug Toppin
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