On 1/15/19 1:51 AM, Christophe Lyon wrote:
> On Mon, 14 Jan 2019 at 20:59, Jason Merrill <jason@redhat.com> wrote:
>> On 12/23/18 9:27 PM, Tom Honermann wrote:
>>> Attached is a revised patch that addresses changes in P0482R6 as well as
>>> feedback provided by Jason.  Changes from the prior patch include:
>>> - Updated the value of the __cpp_char8_t feature test macro to 201811
>>>     per P0482R6.
>>> - Enable char8_t support with -std=c++2a per adoption of P0482R6 in
>>>     San Diego.
>>> - Reverted the unnecessary changes to gcc/gcc/c/c-typeck.c as requested
>>>     by Jason.
>>> - Removed unnecessary checks of 'flag_char8_t' within the C++ front
>>>     end as requested by Jason.
>>> - Corrected the regression spotted by Jason regarding initialization of
>>>     signed char and unsigned char arrays with string literals.
>>> - Made minor changes to the error message emitted for ill-formed
>>>     initialization of char arrays with UTF-8 string literals.  These
>>>     changes do not yet implement Jason's suggestion; I'll follow up with a
>>>     separate patch for that due to additional test impact.
>>>
>>> Tested on x86_64-linux.
>> I just applied the compiler changes with small modifications, as
>> follows; thank you very much for the patches.  Jonathan should check in
>> the library portion before long.
>>
>> Jason
> Hi,
>
> The new testcase g++.dg/ext/utf-cvt-char8_t.C fails at least on arm and aarch64:
>
> g++.dg/ext/utf-cvt-char8_t.C  -std=gnu++14  (test for warnings, line 24)
> g++.dg/ext/utf-cvt-char8_t.C  -std=gnu++17  (test for warnings, line 24)

Arm and aarch64 have unsigned char by default, so the warning 
("conversion to 'char' from 'char8_t' may change the sign of the 
result") isn't emitted on those platforms.  I presume adding 
'-fsigned-char' to the options for the test would be a sufficient fix?  
If so, a patch is attached.

Tom.

>
> Christophe