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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: What exactly is the licensing situation with GNAT?
Date: Fri, 14 Nov 2014 16:24:14 -0600
Organization: Jacob Sparre Andersen Research & Innovation
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Xref: news.eternal-september.org comp.lang.ada:23330
Date: 2014-11-14T16:24:14-06:00
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"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message 
news:fo7cw4s3dd6g$.1jh55iopdn64m$.dlg@40tude.net...
> On Thu, 13 Nov 2014 15:51:54 -0600, Randy Brukardt wrote:
>
>> I recall Adam suggesting that some special sort of named
>> access-to-subprogram type be defined with similar characteristics to the
>> anonymous access-to-subprogram. Such a thing could be made to work, while
>> the bare pointer used for normal access-to-subprogram types would not 
>> work.
>> But of course it would be susceptible to dangling pointers, and won't
>> (usually) be compatible with C.
>
> I was always wondering why it was not a plain subprogram type. That would
> solve a lot of problem, interfacing C included. E.g.

I don't know why it is an access rather than just directly a type. Perhaps a 
lack of imagination? But there's insufficient difference to justify the 
change today.

OTOH, I don't see why this would be any different than access types 
vis-a-vis interfacing with C and the like. The type would have a 
representation (likely one similar to access-to-subprogram), and that's the 
problem for 'Unrestricted_Access - it needs a different representation to 
support 'Unrestricted_Access from 'Access. And the representation needed for 
'Unrestricted_Access is incompatible with C (other than on GCC, which is 
unusual). If you simply allowed any subprogram to match a subprogram type, 
you couldn't allow interface to C. Or you'd have to have an accessibility 
check on the use only for interface to C. Or some other messy rule - would 
not gain anything.

                                            Randy.