Path: news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail From: olcott Newsgroups: comp.theory Subject: Incorrect requirements --- Computing the mapping from the input to HHH(DD) Date: Thu, 8 May 2025 12:00:39 -0500 Organization: A noiseless patient Spider Lines: 156 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 19:00:41 +0200 (CEST) Injection-Info: dont-email.me; posting-host="f36da193996cadd52a214445b52881fc"; logging-data="2081451"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18yAW478uZQPkxxCUABGfGu" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:fzhCkAJSiJxRSlOHcPTVRV7/v+M= X-Antivirus: Norton (VPS 250508-4, 5/8/2025), Outbound message In-Reply-To: X-Antivirus-Status: Clean Content-Language: en-US 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* When HHH(DD) computes the actual mapping from its actual input to the actual behavior this it specifies it must be according to the rules of the x86 language. int sum(int x, int y) { return x + y; } sum is required to compute the mapping from its input into its return value according to the rules of arithmetic. This means that requiring sum(3,2) to return the sum of 5 + 7 is an incorrect requirement. Like sum(3,2) HHH(DD) is only allowed to report on the behavior that its input actually specifies. -- Copyright 2024 Olcott "Talent hits a target no one else can hit; Genius hits a target no one else can see." Arthur Schopenhauer