Re: [PATCH] stdlib: Suppress gcc diagnostic that char8_t is a keyword in C++20 in uchar.h.

[Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>]

On 29/07/22 15:22, Tom Honermann wrote:
> On 7/25/22 8:34 AM, Adhemerval Zanella Netto via Libc-alpha wrote:
>>
>> On 25/07/22 06:07, Florian Weimer wrote:
>>> * Tom Honermann via Libc-alpha:
>>>
>>>> gcc 13 issues the following diagnostic for the uchar.h header when the
>>>> -Wc++20-compat option is enabled in C++ modes that do not enable char8_t
>>>> as a builtin type (C++17 and earlier by default; subject to _GNU_SOURCE
>>>> and the gcc -f[no-]char8_t option).
>>>>    warning: identifier ‘char8_t’ is a keyword in C++20 [-Wc++20-compat]
>>>> This change modifies the uchar.h header to suppress the diagnostic through
>>>> the use of '#pragma GCC diagnostic' directives for gcc 10 and later (the
>>>> -Wc++20-compat option was added in gcc version 10).  Unfortunately, a bug
>>>> in gcc currently prevents those directives from having the intended effect
>>>> as reported at https://gcc.gnu.org/PR106423.  A patch for that issue has
>>>> been submitted and is available in the email thread archive linked below.
>>>>    https://gcc.gnu.org/pipermail/gcc-patches/2022-July/598736.html
>>>> ---
>>>>   wcsmbs/uchar.h | 8 ++++++++
>>>>   1 file changed, 8 insertions(+)
>>>>
>>>> diff --git a/wcsmbs/uchar.h b/wcsmbs/uchar.h
>>>> index c37e8619a0..5f7139f279 100644
>>>> --- a/wcsmbs/uchar.h
>>>> +++ b/wcsmbs/uchar.h
>>>> @@ -34,8 +34,16 @@
>>>>   /* Declare the C2x char8_t typedef in C2x modes, but only if the C++
>>>>     __cpp_char8_t feature test macro is not defined.  */
>>>>   #if __GLIBC_USE (ISOC2X) && !defined __cpp_char8_t
>>>> +#if __GNUC_PREREQ (10, 0) && defined __cplusplus
>>>> +/* Suppress the diagnostic regarding char8_t being a keyword in C++20.  */
>>>> +# pragma GCC diagnostic push
>>>> +# pragma GCC diagnostic ignored "-Wc++20-compat"
>>>> +#endif
>>>>   /* Define the 8-bit character type.  */
>>>>   typedef unsigned char char8_t;
>>>> +#if __GNUC_PREREQ (10, 0) && defined __cplusplus
>>>> +# pragma GCC diagnostic pop
>>>> +#endif
>>>>   #endif
>>> Patch looks okay to me.  The warning was introduced in GCC 10.
>>>
>>> This needs RM approval at this point, I think.
>>>
>>> Thanks,
>>> Florian
>>>
>> This is ok for 2.36, thanks.
> Thanks. Please commit on my behalf; I don't have commit access.
> 
> Tom.
> 

Ack, done.