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From: Mikko <mikko.levanto@iki.fi>
Newsgroups: comp.theory
Subject: Re: Overcoming the proof of undecidability of the Halting Problem by a simple example in C
Date: Mon, 19 May 2025 12:29:09 +0300
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On 2025-05-18 22:18:06 +0000, Ben Bacarisse said:

> Richard Heathfield <rjh@cpax.org.uk> writes:
> ...
>> If they know C they should know that it's
>> u32 HHH(void (*P)()), according to Halt7.c.
>> 
>> It takes a pointer to a function that accepts no arguments and returns no
>> value.
> 
> Yes, but I am surprised that you are being so modern!!  You used to
> favour C90 and didn't really care for anything more recent.

I havn't used C for a long time. Therefore I have had no need to care
about the newer version. But I don't see anything wrong in them, the
new features seem useful even if it is unlikely I will yuse them
myself.

> Empty ()s in a declarator were made obsolete in C17 and made equivalent
> to (void) in C23.  Prior to C23 a parameter that is pointer to a
> function taking no arguments would have to have been written as
> 
>   u32 HHH(void (*P)(void))
> 
> and after C23 the (probable) intended meaning would have to be written
> as
> 
>   u32 HHH(void (*P)(...))
> 
> (Caveat: I'm not properly up to date anymore and, this not being
> comp.lang.c, I may not be corrected by People Who Really Know.)

I'll ask there if I really need to know.

-- 
Mikko