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From: David Thompson <dave.thompson2@verizon.net>
Newsgroups: comp.lang.ada
Subject: Re: Interfacing to C: big structures
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On Tue, 26 Feb 2008 20:28:48 -0500, Robert A Duff
<bobduff@shell01.TheWorld.com> wrote:

> "Alex R. Mosteo" <amosteo@unizar.es> writes:

> > And, finally, is adding an alignment clause enough to solve this issue?
> > If so, how do you query the alignment of a C datatype?
> 
> I'm not a C expert, but I don't think there's any easy way.
> 
Easy is a matter of opinion, and not very elegant, but possible:

#include <stddef.h> 
struct S { whatever };
size_t /* or other u-int type */ Alignment_for_S (void)
{
  struct trick { char x; S y; } /* type only no instance */;
  return offsetof (struct trick, y);
}

This isn't guaranteed to be minimal, but it is sufficient.

- formerly david.thompson1 || achar(64) || worldnet.att.net