Re: A: a new bug to old plain C

Your mentioned the following text snippet from C standard:
"
6.7.4 Type qualifiers
    6.7.4.1 General

    11 For two qualified types to be compatible, both shall have >>>>>>> the
       identically qualified version <<<<<<< of a compatible type; the
order of
       type qualifiers within a list of specifiers or qualifiers does not
affect the
       specified type.
".

So, the last code sample does a conversion between "non compatible" types
without any error or warning.


ср, 26 нояб. 2025 г. в 12:48, LIU Hao <[email protected]>:

> 在 2025-11-26 17:37, Александр Поваляев 写道:
> > Hi there!
> >
> > The code below works fine on all the GCC compilers. It doesn't provide
> either errors or warnings.
> >
> > "
> > struct zzz {
> > unsigned x, y;
> > };
> >
> >
> > void square(struct zzz * arr_of_ptr, unsigned count) {
> >
> > struct zzz * const ptr1 = arr_of_ptr; // OK!
> > struct zzz const * ptr2 = arr_of_ptr; // OK!
> > struct zzz const * const ptr3 = arr_of_ptr; // OK!
> >
> > }
> > "
>
> These are not the same as your original code. These are pointers to
> 'qualified or unqualified versions of
> compatible type(s)', where the 'compatible type' is `struct zzz *`.
>
> In your original code there's `struct zzz ** arr_of_ptr` which points to
> `struct zzz *`, and there's
> `struct zzz const * const * const end_of_arr` which points to
> const-qualified `struct zzz const *`, so
> those pointers point to incompatible different types, and are not
> convertible.
>
>
>
> --
> Best regards,
> LIU Hao
>