Re: Porting Ada code to Linux

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

On Tue, 31 Oct 2006 09:38:14 -0800, Howard wrote:

> I work with Bill, and I wanted to provide a more detailed expansion of
> our situation;
> 
> We are porting from a Windows-95 "legacy" system to a new Linux one.
> The code we are re-writing is Visual Basic, and we are translating it
> into C++.  But, the VB code had a dependancy on a considerable amount
> of Ada 95 code that the VB code interfaced with via DLLs.
> 
> We need to port this Ada code over, also.  We have decided, given that
> there is between 45 and 55 thousand lines of Ada code, with its
> attendant complexity, to simply use the Ada code as is without
> re-writing it into C++.  This Ada code depends on some files, also
> written in Ada, that then have some pragmas to a Visual C++ library,
> "winbase.h"...

Rather than trying to convert the VB into C++, keep the Ada,
convert the Ada into Linux and glue the C++ to the Ada,
why don't you convert the VB into Ada?

You don't seem to have a strong technical reason to combine
C++ and Ada, since C++ isn't a current implementation language.
Because C++ and Ada have similar capabilities ("modern" compiled OO
languages), the technical advantages of mixing them in new
code are minimal.  Mixing languages always has a cost - staff
training, reduced compiler support, tricky interfaces, whatever.

Since you plan to convert to C++, you must have good reasons.
Political?  Skills sets?  Anyone well skilled in both C++ and Ada
would keep it all in the same language (Ada), or have a really
good justification already for mixing (interfacing to existing,
complex C++ libraries without Ada bindings, perhaps).
But since you haven't chosen the Linux libraries yet, this
can't be why.

I suspect you want to move to C++ for a mixture of political
and skills reasons, but this really warrants planning to
rewrite *all* the Ada, in due course.  History suggests this
is an unsound approach when existing code works broadly as needed.
If politics is absent, do it all in Ada, getting necessary
skills from outside.

Just my thoughts.
--
Adrian

PS: If you email me the VB, Ada code, I'll rewrite it in Ada/Linux...
for a small fee.