Re: Attributes 'Version and 'Body_Version

[Kilgallen@SpamCop.net (Larry Kilgallen)]

In article <5ee5b646.0111280749.77fabe6c@posting.google.com>, dewar@gnat.com (Robert Dewar) writes:
> Kilgallen@SpamCop.net (Larry Kilgallen) wrote in message news:<YsaTZ19cOfHh@eisner.encompasserve.org>...

>> Was  the thought that the set of Ada compiler vendors 
>> will always be so small that such issues can be worked 
>> out informally ?
> 
> Not particularly, though this is in practice true. The real
> point is that if you use implementation defined attributes
> and pragmas, you are making your code incompatible with
> other compilers, and that might include compilers for some
> new version of Ada, but in any case that means no more than
> that going to a new version of Ada might be as difficult as
> moving to another vendors compiler for the current version
> of Ada, and we have always used this distance comparison
> as a measure of acceptable levels of incompatibility with
> new versions.

But going to a newer version of the same vendor's compiler
is something programmers expect to be effortless.  If
that vendor implements a new language-defined attribute
rather than its former implementation-defined attribute
which had the same name, the expectation might not be
realized.

> I see no practical issue here, only a theoretical issue
> that in practice is of minimal concern.

The sort of approach I would have expected would be a
division of the namespace.  VMS linker (and other) namespace
segregation is done with a dollar sign.  Not that a dollar
sign is appropriate for Ada, but I would expect some area
set aside into which the language-defined attributes will
not trespass in the future.