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From: olcott <polcott333@gmail.com>
Newsgroups: comp.theory,comp.lang.c
Subject: Re: Every D(D) simulated by H presents non-halting behavior to H ###
Date: Sat, 18 May 2024 13:20:25 -0500
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On 5/18/2024 11:32 AM, James Kuyper wrote:
> On 5/18/24 11:44, Richard Damon wrote:
>> On 5/18/24 11:34 AM, James Kuyper wrote:
>>> On 5/18/24 09:02, Mikko wrote:
>>>> On 2024-05-17 17:14:01 +0000, olcott said:...>>>> Fully operational
> software that runs under Widows and Linux
>>>>> proves that the above is true EMPIRICALLY.
> 
> You cannot prove that code is strictly conforming empirically. It might
> simply happen to work on every system you've tried it on. Have you ever
> tested it on a system where code and data pointers are different sizes?
> 

I use a compiler option to force 32-bit code.

>>>> No, it does not. As the program is not strictly conforming
>>>> and uses a non-standard extension some implementation may
>>>> execute it differently or refuse to execute.
>>>
>>> Which non-standard extension does it use?
>>
>> I think the issue is the casting of a pointer to function to a pointer
>> to object, which is one of the grey areas in the standard. (which occurs
>> in code not shown)
>>
>> It is not specified that such a cast is allowed, but it also isn't
>> specifically disallowed, it is just omitted as a case in the listing of
>> te possibilities for casting.
> 
> Such code has undefined behavior "by the omission of any explicit
> definition of behavior." (4p2).
> Strictly conforming programs cannot have undefined behavior (4p5).

-- 
Copyright 2024 Olcott "Talent hits a target no one else can hit; Genius
hits a target no one else can see." Arthur Schopenhauer