Re: ADA CORE TECHNOLOGIES ANNOUNCES GNAT-TO-JAVA SYSTEM

[stt@houdini.camb.inmet.com (Tucker Taft)]

Stephen Leake (Stephen.Leake@gsfc.nasa.gov) wrote:

: ...
: I guess this is what Intermetrics has; the AdaMagic front end
: accommodates several backends. Is that all written in Ada?

The AdaMagic front end was written in ANSI C.  One reason was to avoid 
the bootstrapping problem, which was profound for us since we
weren't building a general purpose backend, and we wanted to be the
first to validate an Ada 95 compiler (albeit for a 24-bit embedded
target).  

Perhaps more importantly, our target market is vendors selling compilers 
with backends generally written in C, so we felt this would ease 
the ability of our licensees to integrate our front end with their 
back end.  Amusingly enough, our first two backends, the one we ourselves 
wrote for the Patriot ground-systems control computer, and the one 
from Aonix, were both written in Ada (83).

In any case, we ended up writing in a kind of Ada95-ized C, with the 
equivalent of package specs and private types, represented using
visible and private header files and lots of accessor functions, and type 
extension represented using a nested parent component and explicit 
conversion functions, etc.  It has been pretty reliable and maintainable, 
but you still get caught periodically by the annoying C human engineering 
stupidities (gcc "-Wall" helps a little).

The AdaMagic run-time system is written in Ada 95, but run-time systems
generally need to be compiled by the associated compiler
anyway, so there isn't really a "bootstrapping" issue.  And as
mentioned above, our "own" backend is written in Ada 83, as is
our debugger.

Of course, if we could have delayed our start date a few years,
we would have written our front end in Ada 95, and we still have vague 
dreams of incrementally converting it to Ada 95.  On the other hand,
chasing bugs in ANSI C code does provides a nice regular reminder of 
why I prefer Ada ;-).

: -- 
: - Stephe

--
-Tucker Taft   stt@inmet.com   http://www.inmet.com/~stt/
Intermetrics, Inc.  Burlington, MA  USA