A: a new bug to old plain C

[Александр Поваляев]

Hi there!

And again, we are not talking about warnings, some compilers show an error
(so, it just stops compiling), some not.

I believe it should be fixed, because there is a quite evident use-case
when using "const Foo * const * const"  is in the order.

And it is also quite in accordance with the recommendations given (links
mentioned says "don't use const Foo **, cause it might be dangerous").
And what we're doing is not using "const Foo**". We tend to use "const Foo
* const * const" instead.

"const" is one of the cornerstones of C language, which prevents possible
errors and makes programming safer.
 So, it should be handled appropriately.

Respectfully,
Aleksandr G Povaliaev.

сб, 22 нояб. 2025 г. в 21:37, Jonathan Wakely <jwakely.gcc@gmail.com>:

>
>
> On Sat, 22 Nov 2025, 15:18 Александр Поваляев, <apovalyaev@gmail.com>
> wrote:
>
>> Hi there!
>>
>> The links you posted are all about "Don't use Foo** → const Foo**, use const
>> Foo** to const Foo* const* conversion instead"
>> (https://isocpp.org/wiki/faq/const-correctness#constptrptr-conversion,
>> https://c-faq.com/ansi/constmismatch.html).
>> Also, it is being discussed if it is safe or not to use such kind of
>> conversion.
>>
>> But we don't use "Foo** -> const Foo**" conversion anyhow.
>> We use "Foo** -> const Foo * const * const" conversion. So, we just
>> follow the recommendation given and not the opposite. :)
>>
>
>
> And so your code would compile in C++.
>
> But like it says in the C FAQ, the rules for C and C++ are different. C
> does not allow that conversion, even though it would be safe (and C++ does
> allow it).
>
> Here is the relevant part:
>
> "C++ has more complicated rules for assigning const-qualified pointers
> which let you make more kinds of assignments without incurring warnings,
> but still protect against inadvertent attempts to modify const values. C++
> would still not allow assigning a char ** to a const char **, but it would
> let you get away with assigning a char ** to a const char * const *.)"
>
>
>
>
>
>> Anyway some compilers return an error. And this is not the expected
>> behaviour for use. It is A BUG!!!
>>
>
> OK, maybe try a different compiler then.
>
>
>
>
>>
>>>>
>>>>