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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: Allocators design flaw
Date: Sat, 14 Oct 2017 16:56:04 +0100
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Date: 2017-10-14T16:56:04+01:00
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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

>> needs the alignment of int (4 on this Mac)
>> 
>> (aploogies if the C isn't correct)