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From: David Brown <david.brown@hesbynett.no>
Newsgroups: comp.arch
Subject: Re: 80286 protected mode
Date: Thu, 10 Oct 2024 08:31:52 +0200
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On 09/10/2024 23:37, MitchAlsup1 wrote:
> On Wed, 9 Oct 2024 20:22:16 +0000, David Brown wrote:
> 
>> On 09/10/2024 20:10, Thomas Koenig wrote:
>>> David Brown <david.brown@hesbynett.no> schrieb:
>>>
>>>> When would you ever /need/ to compare pointers to different objects?
>>>> For almost all C programmers, the answer is "never".
>>>
>>> Sometimes, it is handy to encode certain conditions in pointers,
>>> rather than having only a valid pointer or NULL.  A compiler,
>>> for example, might want to store the fact that an error occurred
>>> while parsing a subexpression as a special pointer constant.
>>>
>>> Compilers often have the unfair advantage, though, that they can
>>> rely on what application programmers cannot, their implementation
>>> details.  (Some do not, such as f2c).
>>
>> Standard library authors have the same superpowers, so that they can
>> implement an efficient memmove() even though a pure standard C
>> programmer cannot (other than by simply calling the standard library
>> memmove() function!).
> 
> This is more a symptom of bad ISA design/evolution than of libc
> writers needing superpowers.

No, it is not.  It has absolutely /nothing/ to do with the ISA.