Re: is Vax addressing sane today

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Sujet : Re: is Vax addressing sane today
De : niklas.holsti (at) *nospam* tidorum.invalid (Niklas Holsti)
Groupes : comp.arch
Date : 10. Sep 2024, 18:55:37
Autres entêtes
Organisation : Tidorum Ltd
Message-ID : <lkbfgpFamojU1@mid.individual.net>
References : 1 2 3 4 5 6 7 8 9 10 11 12
User-Agent : Mozilla Thunderbird
On 2024-09-10 18:42, Anton Ertl wrote:

And it seems to me that Swift with its trapping arithmetic is a
blast from the past
The dominance of C and its descendants has corrupted the world of programming on this point. :-(
Fortunately, among up-and-coming new languages Rust is in the overflow-checking camp, at least in DEBUG-mode compilations.

(with Algol, Pascal etc. usually erroring out on overflow, and Ada raising an exception (with famously explosive consequences for the Ariane 5)),
A bit misleading, as so often when the Ariane 501 incident is brought up.
The Ariane 501 failure was a HW trap on an instruction converting a floating-point value into a 16-bit integer, not an Ada exception.
As I understand it, the analogous C code could have used the same instruction and failed in the same way (an example of Undefined Behavior)
The original designers of that Ada SW had carefully analysed the possible ranges of the numbers and correctly concluded that an overflow could not happen if the HW operated correctly. Correctly, that is, for the Ariane 4, but not for the Ariane 5 where the SW was sloppily reused through multiple process skimps and failures.
Several other similar conversions were protected with programmed range checks and suitable alternative code paths, but the analysis showed that this particular conversion did not need such checks for the Ariane 4.
One of the process failures was that the SW was never tested with the Ariane 5 launch trajectory, which would have revealed the error.
If the SW had really used Ada exceptions (difficult as the processor was
quite maxed out) a reasonable SW designer would have added an exception
handler and could have made this part of the SW fail gracefully. But
the mission would probably not have been saved because the failure investigation found other potentially fatal flaws in the systems, pointing to more process failures.

and that the trend in safe languages is to eliminate integer overflow
by allowing arbitrarily large integers.
That is not practical in a real-time, resource-limited context, at least not without a large over-provision of computing resources. And sending the resulting over-large integer to a HW register will still fail in some way if the value is too large for the HW to accept.

Date Sujet#  Auteur
5 Sep 24 * is Vax adressing sane today336Brett
5 Sep 24 +* Re: is Vax adressing sane today324John Dallman
6 Sep 24 i+- Re: is Vax adressing sane today1Lawrence D'Oliveiro
6 Sep 24 i`* Re: is Vax adressing sane today322Anton Ertl
6 Sep 24 i +- Re: is Vax adressing sane today1Lawrence D'Oliveiro
6 Sep 24 i +* Re: is Vax adressing sane today5MitchAlsup1
7 Sep 24 i i`* Re: is Vax adressing sane today4Anton Ertl
7 Sep 24 i i `* Re: is Vax adressing sane today3Anton Ertl
7 Sep 24 i i  `* Re: is Vax addressing sane today2John Dallman
7 Sep 24 i i   `- Re: is Vax addressing sane today1Anton Ertl
7 Sep 24 i +* Re: is Vax adressing sane today313John Levine
8 Sep 24 i i`* Re: is Vax adressing sane today312Anton Ertl
8 Sep 24 i i +* Re: is Vax adressing sane today304MitchAlsup1
8 Sep 24 i i i`* Re: is Vax addressing sane today303Lawrence D'Oliveiro
9 Sep 24 i i i +* Re: is Vax addressing sane today231MitchAlsup1
9 Sep 24 i i i i`* Re: is Vax addressing sane today230Brett
9 Sep 24 i i i i +* Re: is Vax addressing sane today7MitchAlsup1
10 Sep 24 i i i i i`* Re: is Vax addressing sane today6Niklas Holsti
11 Sep 24 i i i i i +- Re: is Vax addressing sane today1Lawrence D'Oliveiro
25 Sep 24 i i i i i `* Re: is Vax addressing sane today4Stephen Fuld
25 Sep 24 i i i i i  `* Re: is Vax addressing sane today3Michael S
25 Sep 24 i i i i i   `* Re: is Vax addressing sane today2MitchAlsup1
25 Sep 24 i i i i i    `- Re: is Vax addressing sane today1Niklas Holsti
10 Sep 24 i i i i `* Re: is Vax addressing sane today222Anton Ertl
10 Sep 24 i i i i  +* Re: is Vax addressing sane today4Michael S
10 Sep 24 i i i i  i`* Re: is Vax addressing sane today3Anton Ertl
10 Sep 24 i i i i  i +- Re: is Vax addressing sane today1Niklas Holsti
11 Sep 24 i i i i  i `- Re: is Vax addressing sane today1Michael S
11 Sep 24 i i i i  +* Re: is Vax addressing sane today7Lawrence D'Oliveiro
11 Sep 24 i i i i  i`* Re: is Vax addressing sane today6Michael S
11 Sep 24 i i i i  i `* Re: is Vax addressing sane today5David Brown
11 Sep 24 i i i i  i  +* Re: is Vax addressing sane today2Thomas Koenig
11 Sep 24 i i i i  i  i`- Re: is Vax addressing sane today1David Brown
11 Sep 24 i i i i  i  `* Re: is Vax addressing sane today2David Schultz
13 Sep 24 i i i i  i   `- Re: is Vax addressing sane today1David Brown
11 Sep 24 i i i i  +* Re: is Vax addressing sane today5John Levine
11 Sep 24 i i i i  i`* Re: is Vax addressing sane today4Thomas Koenig
11 Sep 24 i i i i  i +* Re: is Vax addressing sane today2Anton Ertl
11 Sep 24 i i i i  i i`- Re: is Vax addressing sane today1jseigh
11 Sep 24 i i i i  i `- Re: is Vax addressing sane today1John Levine
20 Sep 24 i i i i  `* Re: is Vax addressing sane today205Kent Dickey
20 Sep 24 i i i i   +* Re: is Vax addressing sane today4MitchAlsup1
21 Sep 24 i i i i   i`* Re: is Vax addressing sane today3Lawrence D'Oliveiro
21 Sep 24 i i i i   i `* Re: is Vax addressing sane today2MitchAlsup1
21 Sep 24 i i i i   i  `- Re: is Vax addressing sane today1Lawrence D'Oliveiro
21 Sep 24 i i i i   +* Re: is Vax addressing sane today4Lawrence D'Oliveiro
21 Sep 24 i i i i   i`* Re: is Vax addressing sane today3MitchAlsup1
21 Sep 24 i i i i   i +- Re: is Vax addressing sane today1Niklas Holsti
21 Sep 24 i i i i   i `- Re: is Vax addressing sane today1Lawrence D'Oliveiro
21 Sep 24 i i i i   +* Re: is Vax addressing sane today30MitchAlsup1
21 Sep 24 i i i i   i+* Re: except what, is Vax addressing sane today18John Levine
21 Sep 24 i i i i   ii+- Re: except what, is Vax addressing sane today1Michael S
22 Sep 24 i i i i   ii+* Re: except what, is Vax addressing sane today8Lawrence D'Oliveiro
22 Sep 24 i i i i   iii`* Re: except what, is Vax addressing sane today7Chris M. Thomasson
22 Sep 24 i i i i   iii `* Re: except what, is Vax addressing sane today6MitchAlsup1
22 Sep 24 i i i i   iii  +* Re: except what, is Vax addressing sane today2Lawrence D'Oliveiro
22 Sep 24 i i i i   iii  i`- Re: except what, is Vax addressing sane today1MitchAlsup1
22 Sep 24 i i i i   iii  +- Re: except what, is Vax addressing sane today1Chris M. Thomasson
22 Sep 24 i i i i   iii  `* Re: except what, is Vax addressing sane today2John Dallman
22 Sep 24 i i i i   iii   `- Re: except what, is Vax addressing sane today1MitchAlsup1
22 Sep 24 i i i i   ii+* Re: except what, is Vax addressing sane today5Terje Mathisen
24 Sep 24 i i i i   iii`* Re: except what, is Vax addressing sane today4Lawrence D'Oliveiro
24 Sep 24 i i i i   iii `* Re: except what, is Vax addressing sane today3Chris M. Thomasson
24 Sep 24 i i i i   iii  `* Re: except what, is Vax addressing sane today2MitchAlsup1
16 Oct 24 i i i i   iii   `- Re: except what, is Vax addressing sane today1Chris M. Thomasson
22 Sep 24 i i i i   ii`* Re: except what, is Vax addressing sane today3Lars Poulsen
24 Sep 24 i i i i   ii `* Re: except what, is Vax addressing sane today2Lawrence D'Oliveiro
24 Sep 24 i i i i   ii  `- Re: except what, is Vax addressing sane today1Michael S
22 Sep 24 i i i i   i+* Re: is Vax addressing sane today7Lawrence D'Oliveiro
22 Sep 24 i i i i   ii`* Re: is Vax addressing sane today6MitchAlsup1
22 Sep 24 i i i i   ii +* Re: is Vax addressing sane today3Lawrence D'Oliveiro
22 Sep 24 i i i i   ii i`* Re: is Vax addressing sane today2MitchAlsup1
22 Sep 24 i i i i   ii i `- Re: is Vax addressing sane today1Lawrence D'Oliveiro
22 Sep 24 i i i i   ii `* Re: is Vax addressing sane today2Anton Ertl
23 Sep 24 i i i i   ii  `- Re: is Vax addressing sane today1MitchAlsup1
23 Sep 24 i i i i   i+* Re: is Vax addressing sane today2Stefan Monnier
23 Sep 24 i i i i   ii`- Re: is Vax addressing sane today1MitchAlsup1
25 Sep 24 i i i i   i+- Re: is Vax addressing sane today1MitchAlsup1
12 Oct 24 i i i i   i`- Re: is Vax addressing sane today1Anton Ertl
22 Sep 24 i i i i   +* Re: is Vax addressing sane today4Thomas Koenig
24 Sep 24 i i i i   i`* Re: is Vax addressing sane today3Kent Dickey
24 Sep 24 i i i i   i +- Re: is Vax addressing sane today1Bill Findlay
24 Sep 24 i i i i   i `- Re: is Vax addressing sane today1Thomas Koenig
23 Sep 24 i i i i   +- Re: is Vax addressing sane today1Stefan Monnier
23 Sep 24 i i i i   `* Re: is Vax addressing sane today161Kent Dickey
23 Sep 24 i i i i    +* Re: is Vax addressing sane today11MitchAlsup1
24 Sep 24 i i i i    i+- Re: is Vax addressing sane today1Lawrence D'Oliveiro
24 Sep 24 i i i i    i`* Re: is Vax addressing sane today9Terje Mathisen
24 Sep 24 i i i i    i +* Re: is Vax addressing sane today4Michael S
24 Sep 24 i i i i    i i`* Re: is Vax addressing sane today3Terje Mathisen
24 Sep 24 i i i i    i i `* Re: is Vax addressing sane today2Michael S
24 Sep 24 i i i i    i i  `- Re: is Vax addressing sane today1MitchAlsup1
24 Sep 24 i i i i    i +* Re: is Vax addressing sane today3Stephen Fuld
24 Sep 24 i i i i    i i`* Re: is Vax addressing sane today2MitchAlsup1
25 Sep 24 i i i i    i i `- Re: is Vax addressing sane today1Stephen Fuld
12 Oct 24 i i i i    i `- Re: is Vax addressing sane today1Anton Ertl
24 Sep 24 i i i i    +* Re: is Vax addressing sane today3Terje Mathisen
29 Sep 24 i i i i    i+- Re: is Vax addressing sane today1Michael S
7 Oct 24 i i i i    i`- Re: is Vax addressing sane today1Kent Dickey
25 Sep 24 i i i i    +* Re: is Vax addressing sane today133MitchAlsup1
26 Sep 24 i i i i    i+- Re: is Vax addressing sane today1MitchAlsup1
28 Sep 24 i i i i    i`* Re: is Vax addressing sane today131Lawrence D'Oliveiro
28 Sep 24 i i i i    +* Re: is Vax addressing sane today3George Neuner
7 Oct 24 i i i i    +* Re: is Vax addressing sane today8Kent Dickey
12 Oct 24 i i i i    `* Re: is Vax addressing sane today2Anton Ertl
9 Sep 24 i i i `* Re: is Vax addressing sane today71Anton Ertl
8 Sep 24 i i `* Re: is Vax adressing sane today7Brett
8 Sep 24 i `* Re: is Vax adressing sane today2MitchAlsup1
6 Sep 24 +* Re: is Vax adressing sane today2MitchAlsup1
6 Sep 24 +- Re: is Vax adressing sane today1Lawrence D'Oliveiro
6 Sep 24 `* Re: is Vax adressing sane today8Anton Ertl

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