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From: "Jeffrey R. Carter" <spam.jrcarter.not@spam.not.acm.org>
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Subject: Re: Problem with Position of the enumeration Type
Date: Thu, 24 Jan 2019 21:29:52 +0100
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Xref: reader01.eternal-september.org comp.lang.ada:55363
Date: 2019-01-24T21:29:52+01:00
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On 1/24/19 8:39 PM, Niklas Holsti wrote:
> 
> All compliant compilers, yes. But the question was: if the enumerated index type 
> has gaps in its representation, can there be corresponding gaps (unused 
> intervals of storage units) between the elements of the array, as represented in 
> memory? Or must the elements still be contiguous, except for alignment padding?
> 
> In other words, can the compiled code compute the offset of an array element 
> directly from the representation of the enumerated index value (causing gaps in 
> the array), or must it always first compute the position number of that value, 
> and then compute the offset from the position number (suppressing gaps)?
> 
> This discussion has not yet pointed to an ARM rule that forbids gaps in the 
> array's representation.

In the absence of representation specifications (Component_Size, Pack, 
Convention), AFAIK the only thing that the ARM says about the implementation of 
arrays is that multidimensional arrays must be in row-major order. Other than 
that, it's up to the compiler, so any array could have "gaps", regardless of the 
index subtypes.

-- 
Jeff Carter
"When and now is this guitar piece from Stottlemeyer?
Yes, it's with Mr. Dog in Gertrude's pinball forest."
The World's Funniest Joke
133