Re: [PATCH for-4.15] x86/efi: enable MS ABI attribute on clang

[Jan Beulich <jbeulich@xxxxxxxx>]

On 04.02.2021 11:51, Roger Pau Monné wrote:
> On Thu, Feb 04, 2021 at 11:27:17AM +0100, Jan Beulich wrote:
>> On 03.02.2021 18:58, Roger Pau Monne wrote:
>>> --- a/xen/include/asm-x86/x86_64/efibind.h
>>> +++ b/xen/include/asm-x86/x86_64/efibind.h
>>> @@ -172,7 +172,7 @@ typedef uint64_t   UINTN;
>>>  #ifndef EFIAPI                  // Forces EFI calling conventions 
>>> reguardless of compiler options
>>>      #ifdef _MSC_EXTENSIONS
>>>          #define EFIAPI __cdecl  // Force C calling convention for 
>>> Microsoft C compiler
>>> -    #elif __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 4)
>>> +    #elif __clang__ || __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 
>>> 4)
>>>          #define EFIAPI __attribute__((__ms_abi__))  // Force Microsoft ABI
>>>      #else
>>>          #define EFIAPI          // Substitute expresion to force C calling 
>>> convention
>>>
>>
>> So the problem is that some capable Clang versions set too low
>> a __GNUC_MINOR__ (I'm observing 2 alongside __GNUC__ being 4
>> on Clang5). The way the description and change are written
>> made me rather imply __GNUC__ to not be available at all,
>> which I then thought can't be the case because iirc we use it
>> elsewhere.
> 
> Yes, I also see 4.2 on Clang 11.
> 
> Do you want me to expand the description by adding:
> 
> "Add a specific Clang check because the GCC version reported by Clang
> is below the required 4.4 to use the __ms_abi__ attribute."

I guess adding this is easy enough when done while committing.
Thanks for the addition.

Jan