Re: Ada array vs C pointer (call by reference)

[Keith Thompson <kst-u@mib.org>]

Stephen Leake <Stephe.Leake@nasa.gov> writes:
> Adam Beneschan <adam@irvine.com> writes:
> > On Jun 27, 3:14 pm, Keith Thompson <ks...@mib.org> wrote:
> >> Maciej Sobczak <see.my.homep...@gmail.com> writes:
> >> > On 27 Cze, 18:11, Keith Thompson <ks...@mib.org> wrote:
> >> > > > Ada *cannot* guarantee that Interfaces.C.C_Float is the
> >> > > > *right* float, because it does not verify how the C code
> >> > > > was compiled and there is a lot of freedom given to C
> >> > > > implementers in this area.  Same for all other types.
> >>
> >> > > No, Ada can't guarantee it directly.  Instead, Ada requires the
> >> > > implementation to guarantee it.
> >>
> >> > And how the implementation can guarantee it without mandating the
> >> > representation on the C compiler?
> >>
> >> It doesn't *mandate* the representation used by the C compiler; the
> >> author of the Interfaces.C implementation has to *know* the
> >> representation used by the C compiler.
> >
> > Which is, of course, impossible without a crystal ball.  
> 
> No, the vendor must provide both the Ada compiler and the C compiler.
> Are there any vendors out there that don't?

No, the vendor certainly doesn't have to provide both the Ada compiler
and the C compiler.  The author of the Ada compiler simply has to know
how the C compiler represents the various types, in order to get
Interfaces.C right.  In most cases, the C type representations are
mandated, or at least strongly suggested, by the underlying system.

(GNAT/gcc is the only case I know of where an Ada compiler and a C
compiler come from the same source.)

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Nokia
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