Re: [PATCH] target/i386: floatx80: avoid compound literals in static initializers

[Laszlo Ersek]

On 07/16/20 18:31, Alex Bennée wrote:
> 
> Laszlo Ersek <lersek@redhat.com> writes:
> 
>> Quoting ISO C99 6.7.8p4, "All the expressions in an initializer for an
>> object that has static storage duration shall be constant expressions or
>> string literals".
>>
>> The compound literal produced by the make_floatx80() macro is not such a
>> constant expression, per 6.6p7-9. (An implementation may accept it,
>> according to 6.6p10, but is not required to.)
>>
>> Therefore using "floatx80_zero" and make_floatx80() for initializing
>> "f2xm1_table" and "fpatan_table" is not portable. And gcc-4.8 in RHEL-7.6
>> actually chokes on them:
>>
>>> target/i386/fpu_helper.c:871:5: error: initializer element is not constant
>>>      { make_floatx80(0xbfff, 0x8000000000000000ULL),
>>>      ^
>>
>> We've had the make_floatx80_init() macro for this purpose since commit
>> 3bf7e40ab914 ("softfloat: fix for C99", 2012-03-17), so let's use that
>> macro again.
>>
>> Fixes: eca30647fc07
>> Fixes: ff57bb7b6326
>> Link: https://lists.gnu.org/archive/html/qemu-devel/2017-08/msg06566.html
>> Link: https://lists.gnu.org/archive/html/qemu-devel/2020-07/msg04714.html
>> Cc: Alex Bennée <alex.bennee@linaro.org>
>> Cc: Aurelien Jarno <aurelien@aurel32.net>
>> Cc: Eduardo Habkost <ehabkost@redhat.com>
>> Cc: Joseph Myers <joseph@codesourcery.com>
>> Cc: Paolo Bonzini <pbonzini@redhat.com>
>> Cc: Peter Maydell <peter.maydell@linaro.org>
>> Cc: Richard Henderson <rth@twiddle.net>
>> Signed-off-by: Laszlo Ersek <lersek@redhat.com>
>> ---
>>
>> Notes:
>>     I can see that there are test cases under "tests/tcg/i386", but I don't
>>     know how to run them.
> 
> You can run the TCG tests with:
> 
>   make check-tcg
> 
> or more specifically:
> 
>   make run-tcg-tests-i386-linux-user
> 
> there is also a:
> 
>   make check-softfloat
> 
> although in this case nothing is affected.
> 
> softfloat bits:
> 
> Acked-by: Alex Bennée <alex.bennee@linaro.org>

Thank you!
Laszlo