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From: Bart <bc@freeuk.com>
Newsgroups: comp.lang.c
Subject: Re: else ladders practice
Date: Fri, 8 Nov 2024 17:37:20 +0000
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On 08/11/2024 08:45, David Brown wrote:
> On 07/11/2024 13:23, Bart wrote:
>> On 06/11/2024 14:50, David Brown wrote:
>>> On 05/11/2024 23:48, Bart wrote:
>>>> On 05/11/2024 13:29, David Brown wrote:
>>
>>>>> int small_int_sqrt(int x) {
>>>>>      if (x == 0) return 0;
>>>>>      if (x < 4) return 1;
>>>>>      if (x < 9) return 2;
>>>>>      if (x < 16) return 3;
>>>>>      unreachable();
>>>>> }
>>
>>> "unreachable()" is a C23 standardisation of a feature found in most 
>>> high-end compilers.  For gcc and clang, there is 
>>> __builtin_unreachable(), and MSVC has its version.
>>
>> So it's a kludge.

> You mean it is something you don't understand?  Think of this as an 
> opportunity to learn something new.

You don't seem to understand a 'kludge' is. Think of it as a 'hack', 
something bolted-on to a language.

This is from Hacker News about 'unreachable':

"Note that gcc and clang's __builtin_unreachable() are optimization 
pragmas, not assertions. If control actually reaches a 
__builtin_unreachable(), your program doesn't necessarily abort.

Terrible things can happen such as switch statements jumping into random 
addresses or functions running off the end without returning:"

"Sure, these aren't for defensive programming—they're for places where 
you know a location is unreachable, but your compiler can't prove it for 
you."

>> 'dummyelse' is a special version of 'else' that tells the compiler 
>> that control will (should) never arrive there. ATM it does nothing but 
>> inform the reader of that and to remind the author. But later stages 
>> of the compiler can choose not to generate code for it, or to generate 
>> error-reporting code.
>>
> 
> You are missing the point - that is shown clearly by the "int.min".

At least my code will never 'run off the end of a function'.

But, it looks like you're happy with ensuring C programs don't do that, 
by the proven expedient of keeping your fingers crossed.



> You have your way of doing things, and have no interest in learning 
> anything else or even bothering to listen or think.

Ditto for you.

>  Your bizarre hatred 
> of C is overpowering for you

Ditto for your hatred of my stuff.