Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail From: olcott Newsgroups: comp.theory Subject: Re: Incorrect requirements --- Computing the mapping from the input to HHH(DD) Date: Thu, 8 May 2025 14:42:49 -0500 Organization: A noiseless patient Spider Lines: 162 Message-ID: References:

MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Injection-Date: Thu, 08 May 2025 21:42:50 +0200 (CEST) Injection-Info: dont-email.me; posting-host="f36da193996cadd52a214445b52881fc"; logging-data="2173122"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1+JJv7bZ5VT19YagUPb/m1L" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:TFSpVjjk12/7nziEEhecdyRHY54= In-Reply-To: X-Antivirus-Status: Clean X-Antivirus: Norton (VPS 250508-4, 5/8/2025), Outbound message Content-Language: en-US Bytes: 8138 On 5/8/2025 2:04 PM, Fred. Zwarts wrote: > Op 08.mei.2025 om 19:00 schreef olcott: >> On 5/8/2025 11:14 AM, Mike Terry wrote: >>> On 08/05/2025 06:33, Richard Heathfield wrote: >>>> On 08/05/2025 06:22, olcott wrote: >>>>> On 5/7/2025 11:09 PM, Richard Heathfield wrote: >>>>>> On 08/05/2025 02:20, olcott wrote: >>>>>> >>>>>> >>>>>> >>>>>>> Does there exist an HHH such that DDD emulated by >>>>>>> HHH according to the rules of the C programming language >>>>>> >>>>>> Let's take a look. >>>>>> >>>>>> The file is 1373 lines long, but don't worry, because I plan to >>>>>> stop at HHH's first departure from the rules of the C programming >>>>>> language (or at least the first departure I spot). >>>>>> >>>>>> Turn in your songbook if you will to: >>>>>> >>>>>> void CopyMachineCode(u8* source, u8** destination) >>>>>> { >>>>>> u32 size; >>>>>> for (size = 0; source[size] != 0xcc; size++) >>>>>> ; >>>>>> *destination = (u8*) Allocate(size); >>>>>> for (u32 N = 0; N < size; N++) >>>>>> { >>>>>> Output("source[N]: ", source[N]); >>>>>> *destination[N] = source[N]; >>>>>> } >>>>>> ((u32*)*destination)[-1] = size; >>>>>> Output("CopyMachineCode destination[-1]: ", >>>>>> ((u32*)*destination) [-1]); >>>>>> Output("CopyMachineCode destination[-2]: ", >>>>>> ((u32*)*destination) [-2]); >>>>>> }; >>>>>> >>>>> >>>>> deprecated. >>>> >>>> It's not just deprecated. It's hopelessly broken. >>>> >>>> Everybody makes mistakes, and one slip would be all very well, but >>>> you make essentially the same mistake --- writing to memory that >>>> your program doesn't own --- no fewer than four times in a single >>>> function. >>>> >>>>>> I'll ignore the syntax error (a null statement at file scope is a >>>>>> rookie error). >>>>>> >>>>>> Instead, let's jump straight to this line: >>>>>> >>>>>> *destination = (u8*) Allocate(size); >>>>>> >>>>>> On line 79 of my copy of the code, we find: >>>>>> >>>>>> u32* Allocate(u32 size) { return 0; } >>>>>> >>>>>> In C, 0 is a null pointer constant, so Allocate returns a null >>>>>> pointer constant... which is fine as long as you don't try to >>>>>> deref it. So now *destination is NULL. >>>>>> >>>>>> We go on: >>>>>> >>>>>> for (u32 N = 0; N < size; N++) >>>>>> { >>>>>> Output("source[N]: ", source[N]); >>>>>> *destination[N] = source[N]; >>>>>> } >>>>>> >>>>>> *destination[N] is our first big problem (we're ignoring syntax >>>>>> errors, remember). destination is a null pointer, so >>>>>> destination[N] derefs a null pointer. >>>>>> >>>>>> That's a fail. 0/10, D-, go away and write it again. And you / >>>>>> dare/ to impugn other people's C knowledge! Crack a book, for >>>>>> pity's sake. >>>>>> >>>>> >>>>> If you can't even understand what is essentially >>>>> an infinite recursive relationship between two functions >>>>> except that one function can terminate the other then >>>>> you don't have a clue about the essence of my system. >>>> >>>> If you can't even understand why it's a stupendously bad idea to >>>> dereference a null pointer, you have no business trying to teach >>>> anyone anything about C. >>>> >>>> Your code is the work of a programmer so hideously incompetent that >>>> 'programmer' is scarcely a fair word to use. >>>> >>>> When you publish code like that, to even *think* about denigrating >>>> other people's C knowledge is the height of arrogant hypocrisy. >>>> >>> One problem here is that you don't understand how PO's code works. >>> That's to be expected, and PO's response ought to be to explain it so >>> that you understand. Instead he goes off on one of his rants, so >>> blamewise it's really down to PO. >>> >>> PO's halt7.c is compiled (it is not linked), then the obj file is fed >>> as input to his x87utm.exe which is a kind of x86 obj code execution >>> environment. x87utm provides a number of primative calls that >>> halt7.c code can make, such as Allocate(), used to allocate a block >>> of memory for use in halt7.c. Within halt7.c code calls an >>> Allocate() function, and x86utm intercepts that and performs the >>> function internally, then jumps the calling code in halt7.c over the >>> Allocate call where it continues as normal. The call never goes to >>> the implementation of Allocate in halt7.c, so the null pointer >>> dereferencing does not actually occur. There are a whole bunch of >>> similar x86utm primitive operations that work in the same way. >>> >>> PO should have said all that, not me, but it seems he's not >>> interested in genuine communication. >>> >>> Mike. >>> >>> >> >> Thanks for those details, they are correct. >> I try to stay focused on the key essence gist >> of the issue and never delve down into the weeds. >> >> int DD() >> { >> int Halt_Status = HHH(DD); >> if (Halt_Status) >> HERE: goto HERE; >> return Halt_Status; >> } >> >> The key gist of the issue (no weeds involved) >> is that HHH emulated DD according to the rules >> of the x86 language >> >> >> *until H correctly determines that* >> *its simulated D would never stop running unless aborted* >> > > And since H does not correctly determine that its simulated D would > never stop running unless aborted, it is a vacuous statement and > Sipser's agreement does not tell anything. > That is counter factual as any fully qualified C programmer will tell you. void DDD() { HHH(DDD); return; } DDD correctly simulated by any HHH cannot possibly reach its own simulated "return" instruction. -- Copyright 2024 Olcott "Talent hits a target no one else can hit; Genius ========== REMAINDER OF ARTICLE TRUNCATED ==========