Re: Where are returned values stored?

[Kilgallen@SpamCop.net (Larry Kilgallen)]

In article <fpadncjkKI4MV17dRVn-uQ@comcast.com>, "Robert I. Eachus" <rieachus@comcast.net> writes:

> This is a "meta-point" that needs to be made again and again.  Ada 
> compilers use many 'solutions' that assume that "under normal 
> circumstances" performance will be fine.  Normal circumstances for Ada 
> includes decent software engineering practice.  There are lots of 
> 'newbie' questions, like this one, where the answer has to reference 
> software engineering practice to describe WHY things are done the way 
> they are done.
> 
> In this case, the assumption is that in Ada, functions do not normally 
> return 'large' objects, but that large is defined in terms of 
> performance in the execution environment, not some arbitrary limit.  So 
> if a program uses some function that returns a multi-megabyte String, in 
> some execution environments this will be a problem.  But if Integer is a 
> 32-bit type, the language will allow you to try to return a 2 Gigabyte 
> String.  On most hardware, you will fail, but if you are running your 
> program on a 64-bit system with more 4 Gigs of memory, performance won't 
> be bad at all.

Merely having hardware capable of 64-bit addressing does not speed the
copying of that 2 Gigabyte string, so performance might be awful.  On
the other hand, there is a greater likelyhood the program will run to
completion, which is a correctness issue.