Re: Legit Warnings or not

["Randy Brukardt" <randy@rrsoftware.com>]

"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message 
news:1rx6dwrxmc81p.eazb4fjqztox$.dlg@40tude.net...
...
> There exist approaches to this:
>
> 1. The varying component can allocated outside the object. The object 
> would
> keep a reference to it.

This is the only approach that works for Ada (at least as far as I can 
tell). And it already works for Janus/Ada; we've used it as long as we've 
have discriminanted components (late 1980s).

...
> I think that Ada should not try to support this stuff.

Ada *does* support this stuff. As Adam noted, there are rules preventing the 
creation of accesses/renames of/into components that might change size. 
There also are rules supporting allocation/deallocation of objects that have 
multiple parts. So far as I know, those are the only rules needed to do so.

And, as noted, Janus/Ada always has worked this way. I originally thought 
Ada compilers were expected to work this way, because there is no good 
reason not to support this as the default (as noted, some target 
environments might not want such objects, and pragma Restrictions can surely 
be used to prevent them from being generated). But apparently, implementers 
are lazy enough to avoid it, and customers have never pushed hard enough to 
get it added as an option.

                                   Randy.