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From: Richard Heathfield <rjh@cpax.org.uk>
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
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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:
>>
>> <snip>
>>
>>> 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