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From: Victor Porton <porton@narod.ru>
Newsgroups: comp.lang.ada
Subject: Allocators design flaw
Date: Sat, 14 Oct 2017 05:53:13 +0300
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Xref: news.eternal-september.org comp.lang.ada:48444
Date: 2017-10-14T05:53:13+03:00
List-Id: <comp.lang.ada>

It is impossible to properly implement an allocator through a C function 
(such as raptor_alloc_memory() from Raptor C library) which allocates a 
struct and returns the pointer to the allocated struct.

It is because RM13.11(21.5/3) "The Alignment parameter is a nonzero integral 
multiple of D'Alignment..."

(If it were "The Alignment parameter is equal to D'Alignment", then we would 
be able just to check (in Allocate procedure implementation) that

pragma Assert(Dummy_Record'Alignment mod Alignment = 0);
-- where Dummy_Record is an arbitrary C-convention record
-- (as all C records have the same alignment reqs)

So Alignment parameter may be arbitrarily big and the C function alignment 
may not conform to it.

Let us think how to work around (in Ada 202x) of this design flaw.

-- 
Victor Porton - http://portonvictor.org