Re: Waiver question

[Ken Garlington <GarlingtonKE@lmtas.lmco.com>]

Robert I. Eachus wrote:
> 
> In article <33585385.C8D@lmtas.lmco.com> Ken Garlington <GarlingtonKE@lmtas.lmco.com> writes:
> 
>    >  *  Most existing DSP code is in C/C++. Therefore, reuse is easier
>    >    if the new code is also written in C++.
> 
>    >    Anyone have a reason to think this waiver shouldn't be approved?
> 
>    Sure, the first quoted statement indicates the author has no clue.
> 
>    Reuse of C is much easier from Ada than from C.
> 
>    Reuse of C is much, much easier from Ada than from C++.
> 
>    Reuse of C++ is all but impossible if the code requires any other
> compiler, whether for C, Ada, C++, or COBOL.  Note that this is a
> compiler issue--using g++ and gcc or even g++ and gnat is
> significantly easier than using a different underlying technology.
> 
>    Therefore if there is a significant amount of C++ to be reused, you
> need to use one specific compiler, otherwise you are better off with
> Ada 95.

I believe the vendor is proposing using the same compiler used to
develop the existing C++ code, although that's not explicit in the
waiver.

As for Ada 95, there is no such compiler for the TI DSP target
in question, only an Ada 83 compiler.

> 
>     This was to some extent true with Ada 83, but with Ada 95 the
> advantage of using Ada for interfacing to foreign code has
> substantially improved, and not just because there exists a tool for
> creating Ada package specifications from .h files.
> 
>     The real advantage from using Ada comes at link time.  If you have
> two C based products you have to interface to, and they have
> conflicting names in them, you are going to be climbing the wall in C
> or C++.  In Ada 95 you can decide to link your program as separate
> partitions, play compiler specific games in the library structure, or
> actually go into one of the C programs and make changes.  That second
> choice sounds confusing so watch a real example: I have two COTS C
> libraries I want to use in a Windows NT environment.  I can build two
> DLLs, one for the Ada binding to each COTS product, then write the
> rest in Ada.  At this point I don't need to care if there are
> conflicts in the C names used.  (Or it may be the case that one or
> both of the DLLs are provided, and all I have to do is construct the
> corresponding package spec.)

Since the existing C/C++ code was developed by the same vendor, this
should not be an issue.

> 
>     In theory, I can do the same thing in C, or for that matter in
> Visual C++, if I am very careful never to require include files from
> the two COTS packages in the same C source file.  But there are other
> gotchas, and I have been got several times.  For example, if the C
> code for one product replaces a standard c library operation, such as
> malloc, getting things to link properly can be a horror.
> 
> --
> 
>                                         Robert I. Eachus
> 
> with Standard_Disclaimer;
> use  Standard_Disclaimer;
> function Message (Text: in Clever_Ideas) return Better_Ideas is...

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