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From: kilgallen@eisner.decus.org (Larry Kilgallen)
Subject: Re: How do I get this to work??
Date: 1999/01/06
Message-ID: <1999Jan6.074153.1@eisner>#1/1
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References: <76s0dp$1v4$1@nntp3.uunet.ca> <76tbvv$ba5$1@nntp3.uunet.ca>
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 <76uvjt$o0f$1@nnrp1.dejanews.com>
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Date: 1999-01-06T00:00:00+00:00
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In article <76uvjt$o0f$1@nnrp1.dejanews.com>, robert_dewar@my-dejanews.com writes:
> In article <36926c54.2583014@news.pacbell.net>,
>   tmoran@bix.com (Tom Moran) wrote:
>> NO.  'address is non-portable.  For instance, one of the
>> compilers I use regularly uses the full Intel
>> segment:offset form, all 32 bits, for 'address, vs 32
>> bits with (Win32's) implied segment for 'access.
> 
> First, I assume you mean full 48 bits for the
> segment:offset form, since that is what it is in 32-bit
> mode, and surely you are talking about 32-bit mode here.
> 
> If so, that is an extraordinarily bad choice for a compiler
> to make. Why? Because there is loads of legacy code around
> that assumes that an Address value can be passed to C as
> a pointer. A compiler that does not allow this usage is in
> my opinion badly flawed if you want to interface to C using
> it.

For the sake of portability, a compiler should at least flag
all such usages that are not guaranteed to work by the standard
against which it is written.  Not working on the development
platform is a very large hammer, but perhaps it is justified
for Ada 95 where there is a supported mechanism for calling
to some of the other standardized languages.

Also, representation of addresses can vary even on a single
platform, so sometimes you have to know how the other language
code (or portion thereof) was compiled to know how big _it_
thinks an address is.  It would not do to have the C code
stuff a 64 bit address into your 32 bit address variable.

Larry Kilgallen