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

[Tom Honermann <tom@honermann.net>]

On 8/1/22 11:48 AM, Adhemerval Zanella Netto wrote:
>
> On 01/08/22 12:27, Tom Honermann wrote:
>> On 8/1/22 9:38 AM, Adhemerval Zanella Netto wrote:
>>> 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.
>> Thank you! Should this (and H.J. Lu's "missing test-c8rtomb/test-mbrtoc8 dependency" patch) be merged for 2.36? Both appear to have been approved for 2.36 but I don't see them on the release/2.36/master branch at the moment.
> I think I did it [1].

Looks, good, thank you!

Tom.

>
> [1] https://sourceware.org/git/?p=glibc.git;a=shortlog;h=refs/heads/release/2.36/master