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From: Victor Porton <porton@narod.ru>
Newsgroups: comp.lang.ada
Subject: Re: Allocators design flaw
Date: Sat, 14 Oct 2017 19:22:26 +0300
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Date: 2017-10-14T19:22:26+03:00
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Simon Wright wrote:

> Victor Porton <porton@narod.ru> writes:
> 
>> Simon Wright wrote:
>>
>>> Victor Porton <porton@narod.ru> writes:
>>> 
>>>>> If the C struct needs alignment greater than that of the elements of
>>>>> which it is composed (see the AI for example) it would have it.
>>>>
>>>> "it would have it"? What this sequence of English words mean?
>>> 
>>> it would have such an alignment
>>> 
>>>   struct chrs {
>>>     char c[10];
>>>   }
>>> 
>>> only *needs* alignment of 1
>>> 
>>>   struct chrs {
>>>     int last;
>>>     char c[256];
>>>   }
>>
>> No, all C structs share the same alignment.
> 
> I agree that malloc() will always allocate aligned on some boundary
> (16-byte? 32-byte?) but that's not the same as the alignment of the
> struct itself.
> 
> See e.g.
> 
https://en.wikipedia.org/wiki/Data_structure_alignment#Typical_alignment_of_C_structs_on_x86

I want my program to work well with every conformant Ada compiler, not just 
"typically" as you propose.

>>> needs the alignment of int (4 on this Mac)
>>> 
>>> (aploogies if the C isn't correct)
-- 
Victor Porton - http://portonvictor.org