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

[Tom Honermann <tom@honermann.net>]

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.