Re: Brief C23 excursion

Am 16.04.26 um 12:34 schrieb Kevin J. McCarthy:
> On Thu, Apr 16, 2026 at 08:38:50AM +0200, Matthias Andree via Mutt-dev 
> wrote:
>> Am 16.04.26 um 06:52 schrieb Kevin J. McCarthy:
>>>
>>> So... I guess this is C23.  Which I know almost nothing about :-D.  
>>> In any case, we're a long ways away from getting to that level of C 
>>> standard support in Mutt.
>>
>> It's actually a C11 feature that is finally leveraged in the C23 
>> stdlib.h, see https://en.cppreference.com/w/c/language/generic.html 
>> or 
>> https://stackoverflow.com/questions/9804371/syntax-and-sample-usage-of-generic-in-c11 
>> or 
>> https://learn.microsoft.com/en-us/cpp/c-language/generic-selection?view=msvc-170
>
> Thank you, Matthias.  Those links are really helpful.  Starts to turn 
> line noise into something I can understand!


Hi Kevin,


My pleasure, glad to have helped -- and the "magic" is one major selling 
point for upgrading from C99 or older to at least C11 that I learned 
earlier today, and tells me the const correctness problem that fraught 
some of the stdlib.h functions is also a good reason to not wait for C23 
for too long if you can assume up-to-date toolchains on the consumer side.

(I had been more focused on tackling C++ version differences in the 
11/14/17/20 range migrations lately, I didn't follow C much, also 
because the type generic stuff in C99/C11 is most prominently documented 
in the tgmath.h area where a generic function name works for float, 
double, long double so you needn't mess with whether you need fabs for a 
double, fabsf for float or fabsl for long double... had missed that it 
would also help with the void * vs. const void *).

>> 1. C23 CHANGES INCOMPATIBLY how a function _declaration_ without 
>> arguments is interpreted.
>>
>> As of C23, int func() means the same as int func(void), must/will not 
>> take arguments, where C18 and before interpreted "has no prototype, 
>> any number of arguments is fine", although that had been deprecated 
>> since C99 or so.
>
> It wasn't that long ago that I start converting some func() 
> declarations inside mutt to func(void).  I'll count myself lucky that 
> we didn't happen to have those kinds of problems in our configure.ac too!
>

Yep, that cleanup pretty much avoided the impenetrable "fails to compile 
on <moderndistro>" reports or "fails to compile on GCC15".

Cheers,
Matthias