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 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.