A: a new bug to old plain C

Tue Nov 25 11:28:10 GMT 2025

Hi there!

Yes.
Here is the original message from myself: "
struct zzz {
unsigned x, y;
};

void square(struct zzz ** arr_of_ptr, unsigned count) {

*// The first "const" produce an error (not a warning) within some GCC
toolchains, for example ARM GCC trunk (linux), see goldbolt.org
<http://goldbolt.org>*
struct zzz const * const * const end_of_arr = arr_of_ptr + count;

*// Without the first const "struct zzz * const * const end_of_arr =
arr_of_ptr + count;" it works fine!!!*

}
".

So, somebody made this BUG to some GCC toolchains (ARM GCC trunk(linux) and
some others). We need to have it nailed down and fixed somehow.

Respectfully,
Aleksandr G Povaliev.

вт, 25 нояб. 2025 г. в 13:32, Matthias Pfaller <leo@marco.de>:

> 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 <henrik.holst@millistream.com
> >:
> >
> >> 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 <
> >> apovalyaev@gmail.com>:
> >>
> >>> 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 <
> henrik.holst@millistream.com
> >>>> :
> >>>>
> >>>> Den mån 24 nov. 2025 kl 13:40 skrev Александр Поваляев <
> >>>> apovalyaev@gmail.com>:
> >>>>
> >>>>> 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 <
> >>>>> henrik.holst@millistream.com>:
> >>>>>
> >>>>>> 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
> <
> >>>>>> gcc-help@gcc.gnu.org>:
> >>>>>>
> >>>>>>> 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 <
> david.brown@hesbynett.no>:
> >>>>>>>
> >>>>>>>> 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
> >>>>>>>>
> >>>>>>>>
>