Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail From: Richard Heathfield Newsgroups: comp.theory Subject: Re: Formal systems that cannot possibly be incomplete except for unknowns and unknowable Date: Thu, 8 May 2025 06:33:33 +0100 Organization: Fix this later Lines: 99 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 07:33:33 +0200 (CEST) Injection-Info: dont-email.me; posting-host="fc99c878bc8892c2ff7fc287d1c7246a"; logging-data="1637842"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1+a5f8YrM5QOCWKSDoztl6rOEYNSsa/Xlyj+cnIHqTdiw==" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:9bG7ODIYEsAIBgB8C4oW5sJ+xoA= In-Reply-To: Content-Language: en-GB Bytes: 5212 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. -- Richard Heathfield Email: rjh at cpax dot org dot uk "Usenet is a strange place" - dmr 29 July 1999 Sig line 4 vacant - apply within