Re: ada portability

[ted@grebyn.com (Ted Holden)]

In article <522@wrdis03.af.mil> cfranz@wrdis01.af.mil (Claus Franzkowiak) writes:

>   How much portability can I expect from an Ada program, given two different 
>computers with two different operating systems and two different compiler 
>vendors.  Exclude real-time programming from this assumption.  I am using
>validated compilers only.

Consider the following lament from the Adawoe electronic bulletin board,
maintained by the Ada community for the purposes those who enjoy laughing
at them:

 
   Complaint #0365 

   Problem:

   Implementation Options Lead to Non-Portability and

   Non-Reusability.

 

   Discussion:     The LRM allows many implementation
   options and this freedom has lead to numerous
   "dialects" of Ada.  As programs are written to rely on
   the characteristics of a given implementation,
   non-portable Ada code results.  Often, the programmer
   is not even aware that the code is non-portable,
   because implementation differences amy even exist for
   the predefined language features.  Further, it is
   sometimes not impossible to compile an Ada program with
   two different implementations of the same vendor's
   compiler.

 

   Another kind of non-portability is that of the programmer's
   skills,  The user interfaces to Ada compilers have become so
   varied that programmers find it very difficult to move from
   one Ada implementation to another,  Not only does the
   command line syntax vary, but so do program library
   structures, library sharability between users, compiler
   capabilities, capacity limits. etc.

   Importance:     ESSENTIAL

   Current Workarounds:


   Significant amounts of code rewriting, recompilation, and
   testing must be done to get a given Ada program to compile
   and to run successfully using another compiler, if at all
   possible, even on the same host-target configuration.  It
   is very difficult to write a truly portable Ada program.

   Another possible solution to porting an Ada program is for
   a customer to carefully choose a compiler to suit the given
   Ada program, or perhaps collaborate with a vendor to tailor
   the compiler to suit these needs.

   Significant amounts of programmer retraining must occur
   when a different Ada compiler is used.

......................................................

But don't despair;  Ada9x is just around the corner.  About 1997.

Ted Holden
HTE