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

[Philippe Mathieu-Daudé]

On 7/17/20 6:46 PM, Laszlo Ersek wrote:
> On 07/17/20 11:26, Laszlo Ersek wrote:
>> On 07/16/20 17:09, Philippe Mathieu-Daudé wrote:
>>> On 7/16/20 4:42 PM, Laszlo Ersek wrote:
>>>> 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),
>>>>>      ^
>>>
>>> This reminds me of:
>>>
>>> commit 6fa9ba09dbf4eb8b52bcb47d6820957f1b77ee0b
>>> Author: Kamil Rytarowski <n54@gmx.com>
>>> Date:   Mon Sep 4 23:23:06 2017 +0200
>>>
>>>     target/m68k: Switch fpu_rom from make_floatx80() to make_floatx80_init()
>>>
>>>     GCC 4.7.2 on SunOS reports that the values assigned to array members
>>> are not
>>>     real constants:
>>>
>>>     target/m68k/fpu_helper.c:32:5: error: initializer element is not
>>> constant
>>>     target/m68k/fpu_helper.c:32:5: error: (near initialization for
>>> 'fpu_rom[0]')
>>>     rules.mak:66: recipe for target 'target/m68k/fpu_helper.o' failed
>>>
>>>     Convert the array to make_floatx80_init() to fix it.
>>>     Replace floatx80_pi-like constants with make_floatx80_init() as they are
>>>     defined as make_floatx80().
>>>
>>> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
>>>
>>>>
>>>> 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.
>>>
>>> Yeah it is not easy to figure...
>>>
>>> Try 'make run-tcg-tests-i386-softmmu'
>>> but you need docker :^)
>>
>> That worked, thanks! Even without Docker: I just had to add
>>
>>   --cross-cc-i386=gcc
>>
>> to my ./configure flags.
>>
> 
> Also -- I meant to, but I forgot to put "for-5.1" in the subject prefix;
> sorry about that.

Alex, as Paolo is not available, can this go via your tree?

> 
> Laszlo
>