Re: C++, Ada, ...

From	Paul Rubin <no.email@nospam.invalid>
Newsgroups	comp.arch.embedded
Subject	Re: C++, Ada, ...
Date	2021-04-19 12:20 -0700
Organization	A noiseless patient Spider
Message-ID	<87blaagjyc.fsf@nightsong.com> (permalink)
References	(2 earlier) <AaGeI.148580$qHh9.147135@fx18.ams4> <s5h32f$edv$1@dont-email.me> <ie32luFlvghU1@mid.individual.net> <s5hogv$77o$1@dont-email.me> <ie55l3F3ou7U1@mid.individual.net>

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Niklas Holsti <niklas.holsti@tidorum.invalid> writes:
> In Ada... The construction step can assign some initial values that
> can be defined by default (pointers default to null, for example)...
>
>    type Zero_Handler is access procedure;
>    type Counter is record ...
>       At_Zero : Zero_Handler;      -- Default init to null.

Wow, that is disappointing.  I had thought Ada access types were like
C++ or ML references, i.e. they have to be initialized to point to a
valid object, so they can never be null.  I trust or at least hope that
SPARK has good ways to ensure that a given access variable is always
valid.

Debugging null pointer exceptions is a standard time-waster in most
languages that have null pointers.  Is it that way in Ada as well?

Fwiw, I'm not a C++ expert but I do use it.  I try to write in a style
that avoids pointers (e.g. by using references instead), and still find
myself debugging stuff with invalid addresses that I think wouldn't
happen in Ada.  But I've never used Ada beyond some minor playing
around.  It seems like a big improvement over C.  C++ it seems to me
also improves on C, but by going in a different direction than Ada.

I plan to spend some time on Rust pretty soon.  This is based on
impression rather than experience, but ISTM that a lot of Rust is
designed around managing dynamic memory allocation by ownership
tracking, like C++ unique_ptr on steroids built into the language.  That
lets you write big applications that heavily use dynamic allocation
while avoiding the usual malloc/free bugs and without using garbage
collection.  Ada on the other hand is built for high assurance embedded
applications that don't use dynamic allocation much, except maybe at
program initialization time.  So Rust and Ada aim to solve different
problems.

I like to think it is reasonable to write the outer layers of complex
applications in garbage collected languages, with critical or realtime
parts written in something like Ada.  Tim Sweeney talks about this in
his old slide deck "The Next Mainstream Programming Language":

https://www.st.cs.uni-saarland.de//edu/seminare/2005/advanced-fp/docs/sweeny.pdf

The above url currently throws an expired-certificate warning but it is
ok to click past that.

Thread

C++, Ada, ... pozz <pozzugno@gmail.com> - 2021-04-17 17:48 +0200
  Re: C++, Ada, ... David Brown <david.brown@hesbynett.no> - 2021-04-17 18:45 +0200
    Re: C++, Ada, ... Tom Gardner <spamjunk@blueyonder.co.uk> - 2021-04-17 19:55 +0100
      Re: C++, Ada, ... David Brown <david.brown@hesbynett.no> - 2021-04-18 12:53 +0200
        Re: C++, Ada, ... Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-04-18 18:48 +0300
          Re: C++, Ada, ... David Brown <david.brown@hesbynett.no> - 2021-04-18 18:59 +0200
            Re: C++, Ada, ... Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-04-19 13:51 +0300
              Re: C++, Ada, ... David Brown <david.brown@hesbynett.no> - 2021-04-19 14:22 +0200
                Re: C++, Ada, ... Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-04-19 19:16 +0300
                Re: C++, Ada, ... David Brown <david.brown@hesbynett.no> - 2021-04-19 22:19 +0200
                Re: C++, Ada, ... Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-04-20 01:03 +0300
                Re: C++, Ada, ... Richard Damon <Richard@Damon-Family.org> - 2021-04-19 18:09 -0400
                Re: C++, Ada, ... David Brown <david.brown@hesbynett.no> - 2021-04-20 06:58 +0200
                Re: C++, Ada, ... Paul Rubin <no.email@nospam.invalid> - 2021-04-19 23:18 -0700
                Re: C++, Ada, ... David Brown <david.brown@hesbynett.no> - 2021-04-20 09:36 +0200
              Re: C++, Ada, ... Paul Rubin <no.email@nospam.invalid> - 2021-04-19 12:20 -0700
                Re: C++, Ada, ... Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-04-20 00:26 +0300
                Re: C++, Ada, ... Paul Rubin <no.email@nospam.invalid> - 2021-04-19 16:01 -0700
                Re: C++, Ada, ... Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-04-20 10:47 +0300
                Re: C++, Ada, ... Tom Gardner <spamjunk@blueyonder.co.uk> - 2021-04-19 23:30 +0100
    Re: C++, Ada, ... Clifford Heath <no.spam@please.net> - 2021-04-18 08:29 +1000
    Re: C++, Ada, ... Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-04-18 10:39 +0300
      Re: C++, Ada, ... David Brown <david.brown@hesbynett.no> - 2021-04-18 14:59 +0200
        Re: C++, Ada, ... Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-04-18 19:23 +0300
          Re: C++, Ada, ... David Brown <david.brown@hesbynett.no> - 2021-04-18 19:26 +0200
            Re: C++, Ada, ... Tom Gardner <spamjunk@blueyonder.co.uk> - 2021-04-18 19:29 +0100
              Re: C++, Ada, ... David Brown <david.brown@hesbynett.no> - 2021-04-18 22:23 +0200
                Re: C++, Ada, ... Tom Gardner <spamjunk@blueyonder.co.uk> - 2021-04-18 23:09 +0100
                Re: C++, Ada, ... David Brown <david.brown@hesbynett.no> - 2021-04-19 08:56 +0200
                Re: C++, Ada, ... Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-04-19 14:04 +0300
                Re: C++, Ada, ... Dimiter_Popoff <dp@tgi-sci.com> - 2021-04-19 15:16 +0300
                Re: C++, Ada, ... Paul Rubin <no.email@nospam.invalid> - 2021-04-19 12:47 -0700
                Re: C++, Ada, ... Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-04-20 00:37 +0300
                Re: C++, Ada, ... David Brown <david.brown@hesbynett.no> - 2021-04-20 07:50 +0200
                Re: C++, Ada, ... David Brown <david.brown@hesbynett.no> - 2021-04-19 14:26 +0200
            Re: C++, Ada, ... Tom Gardner <spamjunk@blueyonder.co.uk> - 2021-04-18 19:30 +0100
              Re: C++, Ada, ... David Brown <david.brown@hesbynett.no> - 2021-04-18 22:17 +0200
                Re: C++, Ada, ... Tom Gardner <spamjunk@blueyonder.co.uk> - 2021-04-18 23:17 +0100
                Re: C++, Ada, ... David Brown <david.brown@hesbynett.no> - 2021-04-19 08:52 +0200
                Re: C++, Ada, ... Tom Gardner <spamjunk@blueyonder.co.uk> - 2021-04-19 10:08 +0100
                Re: C++, Ada, ... David Brown <david.brown@hesbynett.no> - 2021-04-19 12:15 +0200
                Re: C++, Ada, ... Tom Gardner <spamjunk@blueyonder.co.uk> - 2021-04-19 12:00 +0100
                Re: C++, Ada, ... Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2021-04-19 16:15 +0300
                Re: C++, Ada, ... David Brown <david.brown@hesbynett.no> - 2021-04-19 15:43 +0200
    Re: C++, Ada, ... pozz <pozzugno@gmail.com> - 2021-04-19 18:38 +0200
      Re: C++, Ada, ... Paul Rubin <no.email@nospam.invalid> - 2021-04-19 10:48 -0700
      Re: C++, Ada, ... Tom Gardner <spamjunk@blueyonder.co.uk> - 2021-04-19 19:33 +0100
        Re: C++, Ada, ... Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2021-04-20 15:09 +0300
          Re: C++, Ada, ... Tom Gardner <spamjunk@blueyonder.co.uk> - 2021-04-20 15:29 +0100
      Re: C++, Ada, ... David Brown <david.brown@hesbynett.no> - 2021-04-19 22:48 +0200
        Re: C++, Ada, ... pozz <pozzugno@gmail.com> - 2021-04-19 23:17 +0200
          Re: C++, Ada, ... Paul Rubin <no.email@nospam.invalid> - 2021-04-19 15:55 -0700
            Re: C++, Ada, ... David Brown <david.brown@hesbynett.no> - 2021-04-20 08:21 +0200
          Re: C++, Ada, ... David Brown <david.brown@hesbynett.no> - 2021-04-20 08:20 +0200
  Re: C++, Ada, ... Dave Nadler <drn@nadler.com> - 2021-04-17 21:07 -0400
    Re: C++, Ada, ... Don Y <blockedofcourse@foo.invalid> - 2021-04-17 18:53 -0700
    Re: C++, Ada, ... Tom Gardner <spamjunk@blueyonder.co.uk> - 2021-04-18 09:42 +0100
  Re: C++, Ada, ... dalai lamah <antonio12358@hotmail.com> - 2021-04-18 14:39 +0200

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