Re: Exchanging objects between programs with different inheritance hierarchies

[Jeffrey Carter <jrcarter@acm.org>]

Steven Deller wrote:
> Ada experts,
> We are in the process of trying to convert some code to GNAT that worked
> on another Ada compiler.   The code transmits tagged type objects
> between processes, and uses unchecked conversion at the receiving end to
> convert to the destination object type.  The objects are various types
> derived from a "base" object with identical inheritance "path", but not
> identical inheritance hierarchies.  
> 
> Using unchecked_conversion depends on the tags being integral to the
> record structures.  On GNAT they are not, so the code fails.
> 
> The code is clearly incorrect Ada.

Had the code used composition rather than type extension this problem 
would not have arisen.

-- 
Jeff Carter
"Mr. President, we must not allow a mine-shaft gap!"
Dr. Strangelove