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Newsgroups: comp.lang.ada
Date: Wed, 11 Dec 2019 13:12:17 -0800 (PST)
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Subject: Re: Is this actually possible?
From: Lucretia <laguest9000@googlemail.com>
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Xref: reader01.eternal-september.org comp.lang.ada:57711
Date: 2019-12-11T13:12:17-08:00
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On Wednesday, 11 December 2019 19:58:54 UTC, Dmitry A. Kazakov  wrote:
> On 2019-12-11 18:54, Lucretia wrote:
> > On Wednesday, 11 December 2019 17:38:40 UTC, Dmitry A. Kazakov  wrote:
> >> On 2019-12-11 17:43, Lucretia wrote:
> >>
> >>> I was thinking about extensible records recently (not tagged types), and thought to try to export a tagged type to C, not C++. It compiles, but the results aren't quite right, so wondering if it's possible or not.
> >>>
> >>> The idea is to export an array of tagged types as a C array to either a function or a variable / struct element. i.e.
> >>
> >> Ada objects of tagged types have varying size and keep tag inside. Both
> >> make them utterly incompatible with C.
> > 
> > I know this, but as the compiler let it go through, I wondered if the tag would be stored elsewhere and not with the tagged type.
> 
> Not with tagged types which have T <-> T'Class view conversions.
> 
> > Otherwise, shouldn't the compiler complain?
> 
> No idea.
> 
> If you need objects that could be packed into C arrays use a variant 
> record with the choice discriminant having a default.

But in my cases, a variant cannot be used.