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

[Jan Beulich <jbeulich@xxxxxxxx>]

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.

Jan