Re: A: a new bug to old plain C

You are aware, that you are quoting the C++-FAQ? Aren't we talking about C?

Congratulations btw, you are (I think) the first person managing to exhaust 
Jonathan's patience. I always thought he had a limitless source of patience hidden 
somewhere and envied him for it...

On 2025-11-25 11:24, Александр Поваляев via Gcc-help wrote:
> We're not converting "Foo** -> const Foo**". We are doing "Foo** -> const
> Foo * const * const" conversion and this works fine (according to the right
> the same
> https://isocpp.org/wiki/faq/const-correctness#constptrptr-conversion which
> was mentioned).
>
> So, what we're doing is correct from both language syntax and coding
> practices (safe coding) points of view.
> This bug should be reported and fixed!!!
>
> Respectfully,
> Aleksandr G Povaliaev.
>
> пн, 24 нояб. 2025 г. в 20:49, Henrik Holst <[email protected]>:
>
>> no they are not, they are a WIKIfication of the C specification, in
>> particular the heading "Why am I getting an error converting a Foo** →
>> const Foo**?" in an official FAQ from the C Standards Committee should make
>> you realize this.
>>
>> /HH
>>
>> Den mån 24 nov. 2025 kl 18:45 skrev Александр Поваляев <
>> [email protected]>:
>>
>>> The articles mentioned are all about coding practices ("safe" and
>>> "unsafe"). They are not about bugs in compilers and hard restrictions being
>>> placed on where I can use "const" in my code and where I can't. :)
>>>
>>> The links mentioned earlier just give a recommendation to use "Foo** ->
>>> const Foo * const *" conversion instead of "Foo** -> const Foo**".
>>> Literally, what I am saying is that: "if you can use const, you should
>>> use it". And this is the case which just confirms my attitude.
>>> But again, this is about coding practices and recommendations. There is
>>> no place in C and C++ standards saying "DON"T USE CONST EVEN IF YOU CAN DO
>>> IT. WE'RE PROHIBITING THIS".
>>>
>>> And so, what GCC compiler (+ some SDKs) is doing now is just the opposite
>>> to the recommendation mentioned. It restricts the places where "const"
>>> might be used.
>>> Anyway, it is a BUG (BIG BUG!!!) in the GCC + SDK. And the BUG was not
>>> made intentionally to protect software engineers from using "unsafe coding
>>> practices" :)))))
>>> For such kind of practices, there are warnings with information messages.
>>> And the bug in GCC should be (1) reported; (2) nailed down and (3) fixed.
>>>
>>> Respectfully,
>>> Aleksandr G Povaliaev.
>>>
>>>
>>> пн, 24 нояб. 2025 г. в 16:10, Henrik Holst <[email protected]
>>>> :
>>>>
>>>> Den mån 24 nov. 2025 kl 13:40 skrev Александр Поваляев <
>>>> [email protected]>:
>>>>
>>>>> Hi there!
>>>>>
>>>>> "False sense of security". Const is a hint to any C compiler to make
>>>>> code more error-prone. So, it is always better to use as much "const" as
>>>>> possible.
>>>>> My point is that "if const might be used, it SHOULD be used". That is
>>>>> the cornerstone.
>>>>> I want to use it, so GCC compiler + SDK should make it possible. It is
>>>>> my code and my design decisions being undertaken.
>>>>>
>>>>> All discussions if it is possible to overcome or not "Const"
>>>>> restriction is irrelivant here.
>>>>>
>>>> no it is not irrelevant here because if I declare a variable as const in
>>>> my local code the value should not be changed by other code either, look at
>>>> the code in the link given to you earlier which shows just such a case as
>>>> an example on why this is not allowed in C.
>>>>
>>>> /HH
>>>>
>>>>> Respectfully,
>>>>> Aleksandr G Povaliaev.
>>>>>
>>>>> пн, 24 нояб. 2025 г. в 13:46, Henrik Holst <
>>>>> [email protected]>:
>>>>>
>>>>>> The things is that this is unsafe and invalid due to it creating a
>>>>>> false sense of security. Aka your "const Foo *" can change under your feet
>>>>>> by _other_ code leading to your const here giving you a false sense of
>>>>>> security. Yes it prevents you from modifying it locally but not some other
>>>>>> code or thread from modifying your const pointer to now point to something
>>>>>> else, hence the compiler issues an error here since you do not get what you
>>>>>> think you are getting.
>>>>>>
>>>>>> /HH
>>>>>>
>>>>>> Den mån 24 nov. 2025 kl 11:10 skrev Александр Поваляев via Gcc-help <
>>>>>> [email protected]>:
>>>>>>
>>>>>>> Hi there!
>>>>>>>
>>>>>>> The code is not invalid and neither of the links posted saying that
>>>>>>> "const
>>>>>>> Foo * const * const" is invalid construction for C.
>>>>>>> The links posted just are discussing that it might be UNSAFE to cast
>>>>>>> "Foo
>>>>>>> **" -> "const Foo **" and recommending usage of "Foo **" -> "const
>>>>>>> Foo *
>>>>>>> const *" instead.
>>>>>>> It's OK. If you feel that it is unsafe, please don't use it. It is
>>>>>>> your own
>>>>>>> decision.
>>>>>>>
>>>>>>> But the syntax itself "const Foo * const * const" is correct and the
>>>>>>> use-case I mentioned is quite simple and evident.
>>>>>>> And so I need this code snipped to be compiled transparently over all
>>>>>>> the
>>>>>>> GCC (and platform SDKs) available versions.
>>>>>>>
>>>>>>> Respectfully,
>>>>>>> Aleksandr G Povaliaev.
>>>>>>>
>>>>>>>
>>>>>>> пн, 24 нояб. 2025 г. в 01:48, David Brown <[email protected]>:
>>>>>>>
>>>>>>>> On 23/11/2025 21:45, Александр Поваляев via Gcc-help wrote:
>>>>>>>>> Hi there!
>>>>>>>>>
>>>>>>>> This is getting /extremely/ frustrating.  /Please/ find some way to
>>>>>>>> learn the C programming language - courses, books, good online
>>>>>>> resources.
>>>>>>>> And /please/ believe me when I say that people who have worked with
>>>>>>> C
>>>>>>>> and C++ for decades, studied the standards, who serve on the
>>>>>>> standards
>>>>>>>> committee, know better about these things than you do.  (I'm talking
>>>>>>>> about Jonathan here, not myself - he really is a world-class expert
>>>>>>> here.)
>>>>>>>>> Either the links you've provided or the links you provided earlier
>>>>>>>>> (yesterday) are irrelevant, cause they are just discussing if it
>>>>>>> is safer
>>>>>>>>> to convert "Foo_Type **" to "const Foo_Type **" or not.
>>>>>>>>>
>>>>>>>> The links are highly relevant.  They explain why you cannot convert
>>>>>>> from
>>>>>>>> "char **" to "const char **".  That also explains why you cannot
>>>>>>> convert
>>>>>>>> from "char **" to "const char * const * const".  Adding even more
>>>>>>>> "const" qualifiers to the invalid conversion does not somehow
>>>>>>> magically
>>>>>>>> make it work.
>>>>>>>>
>>>>>>>>> Once again, we are not converting "char** to const char**", we're
>>>>>>>>> converting char** to const char * const * const".
>>>>>>>>> And we're not discussing if it is safer or not, we are discussing
>>>>>>> GCC
>>>>>>>>> compiler error.
>>>>>>>>>
>>>>>>>> The compiler is generating an error message because you wrote
>>>>>>> invalid
>>>>>>>> code.  The error - or bug, if you like - is in /your/ code.  Not the
>>>>>>>> compiler.  GCC is doing its job correctly here.
>>>>>>>>
>>>>>>>>> Respectfully,
>>>>>>>>> Aleksandr G Povaliaev.
>>>>>>>>>
>>>>>>>> I'm sorry, but signing the post with "respectfully" does not make it
>>>>>>>> respectful.  You started the thread disrespectfully - insisting that
>>>>>>>> there is a bug in GCC when you simply do not understand the relevant
>>>>>>>> aspects of the C programming language.  And you have gone downhill
>>>>>>> since
>>>>>>>> then, ignoring and rejecting the help and advice you have been
>>>>>>> given.
>>>>>>>> Getting things wrong once is entirely understandable - this is a
>>>>>>> subtle
>>>>>>>> point of the C language, and you are posting to a "help" list.
>>>>>>> Doubling
>>>>>>>> down on your ignorance when you have received the help and
>>>>>>> information
>>>>>>>> you need, is a different matter entirely.
>>>>>>>>
>>>>>>>> Your code is flawed.  You need to fix it.  Mindlessly repeating your
>>>>>>>> misunderstandings about how you think C works will not do anything
>>>>>>> but
>>>>>>>> annoy people.
>>>>>>>>
>>>>>>>> David
>>>>>>>>
>>>>>>>>