Re: Automated conversion to C++?

["Dr. Adrian Wrigley" <amtw@linuxchip.demon.co.uk.uk.uk>]

On Fri, 15 Feb 2008 14:33:08 +0100, Jacob Sparre Andersen wrote:

> I have been offered to take part in a programming project with a
> rather annoying constraint: There should be C++ source available for
> the constructed program.
> 
> The good part is that I am allowed to do the actual programming in
> Ada, and just use an automated translator to generate the C++ code.

If you have to supply a C++ program semanticly equivalent to the binary
you deliver, the best choice is to write it in pure C (or C++).

You are guaranteed equivalence.  You need find no translators.  You
have no mismatches in runtime. The risk is low.

C++ makes so many Ada capabilities a real nuisance to implement.
Basics like enumerations with constraint checks, fixed point types,
floating point attributes, integer over/underflow exceptions
need loads of messy C++ (often with specialized headers) to implement.

When it comes to rendezvous, elaboration, real-time, ATC and anything
from Annex E,(or D or G), you are really stuck with no obvious mapping.

If you are interfacing to hardware, you hit the limitation that you
can't do representation clauses in C++.  The nearest thing is by
unpacking bit fields manually, making assumtions about the layout
in C++ (which are not part of the language spec).

In short, to deliver a C++ program:

Simple program  => Write it in C because translation takes too much time
Complex program => Write it in C because the translation is impossible

If a customer is paying to get C++ source, don't write it in Ada - they
presumably don't care for a robust, low-defect solution.  If they did,
they would put constraints on the C++ (eg must run at least 80% of the
speed.  Use no more than 1.3x the memory)

Just my opinion.
--
Adrian