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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: How do typical Ada calling conventions work ?
Date: Mon, 24 Aug 2015 17:03:55 -0500
Organization: JSA Research & Innovation
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Xref: news.eternal-september.org comp.lang.ada:27598
Date: 2015-08-24T17:03:55-05:00
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"Hadrien Grasland" <hadrien.grasland@gmail.com> wrote in message 
news:2541f7b7-b728-421b-96cf-e0d656e984a2@googlegroups.com...
...
>Thanks for your answers ! These are some pretty nice ways to do it instead 
>indeed.
>
>I'm glad the secondary stack approach won in the end for GNAT, it sounds 
>more
> efficient, clean and scalable than what they were attempting in the 
> beginning.

I doubt that. The scheme Janus/Ada uses is much simpler: the memory is 
allocated off of a special storage pool and it is then freed using the same 
mechanism that does other finalization (indeed, the memory management [which 
we used in Ada 83] was repurposed to do finalization, rather than the other 
way around).

This is probably not as efficient as the secondary stack approach, but I 
find that irrelevant in 99.9% of programs. All functions that return 
non-elementary types are somewhat more expensive than the similar parameter 
passing, so if efficiency is a primary concern, one must use procedures 
rather than functions. The cases where function return by secondary stack 
would be efficient enough but function return by heap is not efficient 
enough are going to be quite rare [in the vast majority of cases either both 
are good enough or neither are] -- thus there are better things to spend 
effort on.

                                                    Randy.