[U-Boot] [PATCH v8 14/30] efi: Don't build sandbox with __attribute__((ms_abi))

[Alexander Graf <agraf@suse.de>]

On 22.06.18 21:28, Simon Glass wrote:
> Hi Alex,
> 
> 
> On 22 June 2018 at 06:11, Alexander Graf <agraf@suse.de> wrote:
>> On 06/21/2018 09:45 PM, Simon Glass wrote:
>>>
>>> Hi Alex,
>>>
>>> On 21 June 2018 at 03:59, Alexander Graf <agraf@suse.de> wrote:
>>>>
>>>> On 06/21/2018 04:02 AM, Simon Glass wrote:
>>>>>
>>>>> Hi Alex,
>>>>>
>>>>> On 20 June 2018 at 02:56, Alexander Graf <agraf@suse.de> wrote:
>>>>>>
>>>>>> On 06/20/2018 12:02 AM, Simon Glass wrote:
>>>>>>>
>>>>>>> Hi Alex,
>>>>>>>
>>>>>>> On 18 June 2018 at 08:46, Alexander Graf <agraf@suse.de> wrote:
>>>>>>>>
>>>>>>>> On 06/18/2018 04:08 PM, Simon Glass wrote:
>>>>>>>>>
>>>>>>>>> There appears to be a bug [1] in gcc when using varargs with this
>>>>>>>>> attribute. Disable it for sandbox so that functions which use that
>>>>>>>>> can
>>>>>>>>> work correctly, such as install_multiple_protocol_interfaces().
>>>>>>>>>
>>>>>>>>> [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70955
>>>>>>>>>
>>>>>>>>> Signed-off-by: Simon Glass <sjg@chromium.org>
>>>>>>>>
>>>>>>>>
>>>>>>>> See my patch instead please.
>>>>>>>
>>>>>>> OK I see it now. Do you know what gcc fixes this problem?
>>>>>>
>>>>>>
>>>>>> The bug you found was really just a gcc bug that hit early gcc6
>>>>>> versions.
>>>>>> I
>>>>>> doubt you're running into it :).
>>>>>
>>>>> OK, so in fact gcc does not support varargs problems with the ms_abi?
>>>>
>>>>
>>>> Gcc needs to know whether varargs are sysv varargs or ms varargs. And it
>>>> differentiates between the two with different variable types for va_list.
>>>>
>>> Have you seen the builtin_va_list, etc.
>>
>>
>> I think this sentence is missing content?
> 
> I thought that builtin_va_list and friends would work regardless of
> the calling standard being used. But it looks (from your patch) like
> you have to explicitly use __builtin_ms_va_list. Is that right?

I'm fairly sure builtin_va_list is just gcc's way of mapping the sysv
va_list, but I'm not 100% sure. I can double check with our compiler
people next week.

Either way, I think this patch is good either way. For starters it's not
gcc specific because it uses the normal va_args in the "normal" case.
Also, it's not ambiguous. IMHO things are quite clear when reading the
code if we explicitly differentiate between sysv and ms_abi va_args.


Alex