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From: peter@objy.objy.com (Peter Moore)
Newsgroups: comp.std.c++
Subject: Re: Randomly ordered fields !?!? (Was:
Message-ID: <1990Sep8.154622@objy.objy.com>
Date: 8 Sep 90 22:46:22 GMT
References: <1990Aug27.152540@bert.llnl.gov> <1990Aug28.211752.24905@zorch.SF-Bay.ORG> <1990Aug28.173553@bert.llnl.gov> <1990Sep1.131041.15411@zorch.SF-Bay.ORG>
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Reply-To: peter@objy.com
Organization: Objectivity Inc.
Lines: 34

In article <1990Sep1.131041.15411@zorch.SF-Bay.ORG>,
xanthian@zorch.SF-Bay.ORG (Kent Paul Dolan) writes:

<< I will paraphrase, since the >>'s were getting too deep:  
       If the standard doesn't mandate structure layout, then compiler
	writers will be free to change structure layout over time and
	render all existing stored binary data obsolete
>>

Now hold on.  There may be arguments for enforcing structure layout,
but this sure isn't one of them. If the different releases of the
compiler change the internal representation of structures, then all old
binaries and libraries will become incompatible.  This is immediately
unacceptable to me, without any secondary worries about old binary
data.  If a vendor tried to do that, I would simple change vendors, and
never come back.  And no sane vendor would try such a change.  The
vendor himself has linkers, debuggers, libraries, and compilers for
other languages that all would change, not to mention thousands of
irate customers burning the vendor in effigy.

There are so many things that a vendor could change that would cause
incompatibility:  calling formats, floating point formats, object file
formats, etc..  The vendor could take 3 years to upgrade to ANSI or
insist on supplying non-standard features that can't be turned off.
Structure layout is just a small part.  By your argument, ANSI should
legislate them all, and that is unreasonable and WAY too restrictive on
implementations.

The standard can never protect you from an incompetent or malicious
vendor.  It can only act as a common ground for well intentioned
vendors and customers to meet.

	Peter Moore
	peter@objy.com