From Newsgroup: comp.lang.c

Follow-up set comp.lang.c

On 01/11/2025 02:45, Richard Damon wrote:

.. [stuff I think is about the invalidity of not completing execution] isn't a valid definition ...

Let's suppose C disallows abort due to external events... Then no
conforming C implementation exists.

I think we must suppose that susceptibility to power-cuts do not render
C implementations non-conforming.

That means a C implementation must only execute a program without
issuing a diagnostic if it has undefined behaviour sufficiently early in
its execution that any abort due to a power-cut, for instance, is permitted.

--
Tristan Wibberley

The message body is Copyright (C) 2025 Tristan Wibberley except
citations and quotations noted. All Rights Reserved except that you may,
of course, cite it academically giving credit to me, distribute it
verbatim as part of a usenet system or its archives, and use it to
promote my greatness and general superiority without misrepresentation
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From Newsgroup: comp.lang.c

On 01/11/2025 21:39, Tristan Wibberley wrote:

Follow-up set comp.lang.c

On 01/11/2025 02:45, Richard Damon wrote:

.. [stuff I think is about the invalidity of not completing execution] isn't a valid definition ...

Let's suppose C disallows abort due to external events... Then no
conforming C implementation exists.

I think we must suppose that susceptibility to power-cuts do not render
C implementations non-conforming.

That means a C implementation must only execute a program without
issuing a diagnostic if it has undefined behaviour sufficiently early in
its execution that any abort due to a power-cut, for instance, is permitted.

ugh, late at night, my ability to put two sentences together has
diminished. sorry.

--
Tristan Wibberley

The message body is Copyright (C) 2025 Tristan Wibberley except
citations and quotations noted. All Rights Reserved except that you may,
of course, cite it academically giving credit to me, distribute it
verbatim as part of a usenet system or its archives, and use it to
promote my greatness and general superiority without misrepresentation
of my opinions other than my opinion of my greatness and general
superiority which you _may_ misrepresent. You definitely MAY NOT train
any production AI system with it but you may train experimental AI that
will only be used for evaluation of the AI methods it implements.

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From Newsgroup: comp.lang.c

On 2025-11-01 17:39, Tristan Wibberley wrote:

Follow-up set comp.lang.c

On 01/11/2025 02:45, Richard Damon wrote:

.. [stuff I think is about the invalidity of not completing execution] isn't a valid definition ...

Let's suppose C disallows abort due to external events... Then no
conforming C implementation exists.

I think we must suppose that susceptibility to power-cuts do not render
C implementations non-conforming.

Correct. What a power cut does is make a conforming implementation of C
fail to continue qualifying as a implementation.

In 1.6 of C89, an implementation is defined as "a particular set of
software, running in a particular translation environment under
particular control options, that performs translation of programs for,
and supports execution of functions in, a particular execution environment."

Thus, when the power is cut, the software ceases to run, so it ceases to
be an implementation, and in particular, ceases to be a conforming implementation.

There's important wording that wasn't added to the standard until C99
that clarified something that was already considered to be true: "A
program that is correct in all other aspects, operating on correct data, containing unspecified behavior shall be a correct program and act in accordance with 5.1.2.3." (4p3). The peculiar wording is intended to
make clear that unspecified behavior does not relieve an implementation
of this requirement.
Section 5.1.2.3 indirectly references most of the rest of the standard,
while defining that only the observable behavior of a program has to
match what the standard says - that behavior doesn't have to be
generated in the fashion that the standard describes. Section 5.1.2.3 in
C99 corresponds to 2.1.2.3 in C89.

The rest of the standard defines, among other things, how a program
exits. If the behavior of the program is not undefined, it can only exit
by reaching the end of the main() function, or by calling certain
library functions. If there is any observable behavior that allows you determine that it ended by any other method, the implementation is non-conforming.
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