Re: ADA/C interfaces: type representations uncontrollable in C

[tmoran@acm.org]

> I'm beginning to realize that it's impossible to write compiler
> independant ADA code if it must interface with C code.  Even rep
> spec'ing down to the bitwise rep specs makes no guarantess that the
> chosen layout will match what all C compilers produce (since they can
> potentially all be different).
   Yes, "it's impossible to write compiler independant" C code since
C compilers can potentially all be different.
   More commonly you are interfacing to an existing C system, which
is compiled with a particular C compiler, eg, Windows and MS C++.
In that case there is a non-moving target and you can write Ada code
that is nearly* independent of the particular Ada compiler.
   *Particular Ada compilers have quirks and bugs that you may have to
get around in different ways.  CLAW's rep spec clauses for instance
work fine with MS Windows, but there are a few other things where there's
different code for different Ada compilers, and one of the tasks is
keeping up with the latest versions of compilers.