Ada to C translator

Ada to C translator

[Gabriel Rouzaut]

Does anybody knows any tool to translate Ada source files to
C/C++ source files?. I was looking for it on the net, but I
couldn't find any.

I was told that some Ada compilers use C as intermediate language
before compilation. Does anybody know one?.

Thanks

Re: Ada to C translator

[Larry Kilgallen]

In article <32E4C115.55BD@iies.es>, Gabriel Rouzaut <gabmrou@iies.es> writes:
> Does anybody knows any tool to translate Ada source files to
> C/C++ source files?. I was looking for it on the net, but I
> couldn't find any.

The consensus in comp.lang.ada from the _many_ times this has been
addressed in the past is that no general purpose translator could
be built since the semantics of Ada are a superset of the semantics
of C or C++ (no tasking for example).  Please read archives of the
comp.lang.ada rather than starting the discussion up from scratch.

> I was told that some Ada compilers use C as intermediate language
> before compilation. Does anybody know one?.

I don't know of any, but sometimes such reports are confused due
to the fact that Ada compilers and C compilers use a common back
end.  Examples are GNAT and DEC Ada.  In each case the back end
has to include at least some Ada-specific features, which some
might views as "proof by example" that a general purpose Ada-to-C
translator is not possible.

Larry Kilgallen

Re: Ada to C translator

[Ted Dennison]

Larry Kilgallen wrote:
> 
> In article <32E4C115.55BD@iies.es>, Gabriel Rouzaut <gabmrou@iies.es> writes:
> > Does anybody knows any tool to translate Ada source files to
> > C/C++ source files?. I was looking for it on the net, but I
> > couldn't find any.
> 
> The consensus in comp.lang.ada from the _many_ times this has been
> addressed in the past is that no general purpose translator could
> be built since the semantics of Ada are a superset of the semantics
> of C or C++ (no tasking for example).  Please read archives of the
> comp.lang.ada rather than starting the discussion up from scratch.
> 
> > I was told that some Ada compilers use C as intermediate language
> > before compilation. Does anybody know one?.
> 
> I don't know of any, but sometimes such reports are confused due
> to the fact that Ada compilers and C compilers use a common back
> end.  Examples are GNAT and DEC Ada.  In each case the back end
> has to include at least some Ada-specific features, which some
> might views as "proof by example" that a general purpose Ada-to-C
> translator is not possible.

This is one of the better explanations I have seen on this subject. It
would be a good candidate for inclusion in the c.l.a FAQ (hint hint).



-- 
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Re: Ada to C translator

[Keith Thompson]

In <1997Jan22.062734.1@eisner> kilgallen@eisner.decus.org (Larry Kilgallen) writes:
[...]
> The consensus in comp.lang.ada from the _many_ times this has been
> addressed in the past is that no general purpose translator could
> be built since the semantics of Ada are a superset of the semantics
> of C or C++ (no tasking for example).  Please read archives of the
> comp.lang.ada rather than starting the discussion up from scratch.

I don't agree that a general purpose translator is impossible.  After all,
we know that a general purpose Ada to machine code translator is possible,
and machine code does not inherently support tasking.  The trick is
that you'd have to find a way to support or emulate tasking (and other
Ada-specific features) in the generated C.  The logical way to do this
is to generate calls to runtime support routines, possibly written in Ada.

Of course, this doesn't imply that an Ada to C translator is necessarily a
good idea.  Generating legible and maintainable C from Ada is a daunting
task.  Even if you could do it, it would be sort of like transmuting
gold into lead.  8-)}

There have been proposals to use C as an intermediate language to simplify
porting an Ada compiler to new architectures.  I don't know how practical
this turned out to be.  Note that C code generated as an intermediate
language is almost certain to be illegible and unmaintainable.

-- 
Keith Thompson (The_Other_Keith) kst@aonix.com <http://www.aonix.com> <*>
TeleSo^H^H^H^H^H^H Alsy^H^H^H^H Thomson Softw^H^H^H^H^H^H^H^H^H^H^H^H^H Aonix
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"SPOON!" -- The Tick

Re: C to Ada translator (was: Ada to C translator)

[Howard W. LUDWIG]

Martin Krueger wrote:
> 
> Larry Kilgallen wrote:
> >
> > In article <32E4C115.55BD@iies.es>, Gabriel Rouzaut <gabmrou@iies.es> writes:
> > > Does anybody knows any tool to translate Ada source files to
> > > C/C++ source files?. I was looking for it on the net, but I
> > > couldn't find any.
> >
> > The consensus in comp.lang.ada from the _many_ times this has been
> > addressed in the past is that no general purpose translator could
> > be built since the semantics of Ada are a superset of the semantics
> > of C or C++ (no tasking for example).  Please read archives of the
> > comp.lang.ada rather than starting the discussion up from scratch.
> >
> 
> As Ada is the superset, is it then possible to translate C-code in Ada?
> I could make use of such a translator to facilitate the rewriting of a
> (supposedly buggy) C-library in Ada.
> 
>         M A R T I N
> 
> --
>                                           _____
>  Dr. Martin Krueger                      |.---.|
>  Alcatel SEL AG, TS/PF                   ||___||      |\__/,|   (`\
>  D-70435 Stuttgart                       |o  --|\     |o o  |__ _) )
>                                          :=====: )  _.( T   )  `  /
>  +49 711 821-49003, Fax:46776                   (_ ((_ `^--' /_<  \
>  martin.krueger@stgl.sel.alcatel.de             /_/   `-'(((/  (((/

The Ada FAQ addresses reasons for not translating from language x to Ada. 
 In particular, one basically has an x-based design expressed in Ada 
syntax.  Thus, one does not have the advantages offered by Ada for 
maintnenance, reuse, etc.  Also, the code was probably originally written 
to support optimization by an x compiler but the translated code does not 
typically fit well with optimization by an Ada compiler.  (The 
traditional example between Fortran and Ada 83 involves the use of 
multidimensional arrays and what order the indexes should be in for 
optimized throughput.)

However, the situation discussed in the original post is even more 
troublesome because of the reference to "buggy".  Are the problems 
relatively simple typographical issues (such as == versus = in a 
conditional or how many asterisks for how many levels of pointer 
dereferencing) or are they fundamental design flaws (the boundary between 
the two being rather fuzzy)?  If there is the suspicion of design flaws, 
I expect one would be better off redesigning basically from scratch with 
Ada concepts in mind.  Otherwise, one simply translates flaws from one 
language to Ada and in a manner where Ada cannot offer its usually 
superior error-checking capability.

Perhaps there is in this case an issue of a very large library and only a 
few errors so the only viable way to handle that many lines of code 
within a certain budget or time frame is to get help from an automated 
process.  However, I would be very careful about using that as an excuse 
to not evaluate critically the design from an Ada standpoint and consider 
starting from scratch.  (At least the requirements for what the library 
needs to do should stay intact.)

Howard W. LUDWIG, Ph.D.
Howard_W_Ludwig@ccmail.orl.mmc.com

Re: Ada to C translator

[Robert Dewar]

<<As Ada is so different from C it is quite natural that Ada translated
into C looks horrible to a C programmer :-)  gi-go>>


Well I know there is a smiley there, but still, this statement is highly
misleading. The issue here has to do with much more fundamental issues
than Ada being different from C, it has to do with a mismatch in semantic
level for certain operations that leads to C that looks horrible to
anyone.

For example, because of the need to do overflow checking, we may well
have to translate:

   x := (a * b) + (c * d);

to

   x = PLUSOV (MULTOV (a, b), MULTOV (c,d));

where PLUSOV and MULTOV are macros that use operators like :? to check
for overflow. There are many other such cases to be dealt with.