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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: What is a byte?
Date: Tue, 29 Jul 2014 19:40:56 +0100
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Date: 2014-07-29T19:40:56+01:00
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"Dan'l Miller" <optikos@verizon.net> writes:

> Victor, if you transliterate your specification to say "octet"
> wherever it says "byte" (following ITU's convention to end this
> perennial/chronic silly debate over how big a byte is in C), then the
> answer to your question becomes quite clear: use integer of range {0,
> ..., 255} or {-128, ..., 128} and mask off the upper powers of 2 if
> any, because unsigned char will always be at least 8 bits on modern
> processors, which means that on some processors byte might be 16- or
> 32-bit, but those extra powers of 2 to the left are simply ignored,
> just as they are in the underlying protocol.  (No specification of any
> modern interoperable protocol uses the 2^8 and higher bits in a byte
> if they exist on some arcade hardware.)  Likewise for signed char,
> respecting twos-complement's bias of sign-extension versus
> sign-magnitude's sign bit.

I don't think this is right (not in terms of how the ABI expects a char
to be passed to a function, but in terms of what Victor ought to do).

If the C function takes a char, you should specify
Interfaces.C.char. It's up to the compiler to decide whether that gets
passed in 8 bits, 32 bits, or come to that 9/36 bits on hardware that no
one is remotely likely to encounter (even in an arcade).