Re: [Xen-devel] [PATCH] x86/vmx: fix build with clang 3.8.0

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 09/02/17 13:01, Jan Beulich wrote:
>>>> On 09.02.17 at 13:49, <andrew.cooper3@xxxxxxxxxx> wrote:
>> On 09/02/17 11:33, Roger Pau Monne wrote:
>>> --- a/xen/include/asm-x86/hvm/vmx/vmx.h
>>> +++ b/xen/include/asm-x86/hvm/vmx/vmx.h
>>> @@ -602,15 +602,16 @@ void vmx_pi_hooks_assign(struct domain *d);
>>>  void vmx_pi_hooks_deassign(struct domain *d);
>>>  
>>>  /* EPT violation qualifications definitions */
>>> -typedef union __transparent__ ept_qual {
>>> +typedef union ept_qual {
>> Please can we use
>>
>> typedef __transparent__ union ept_qual {
>>
>> which clang is happy with, and will help avoid problems such as the
>> cper_mce_record issue in c/s f8be76e2fe
> Would clang also be happy with it moved near the end of that
> line
>
> typedef union ept_qual __transparent__ {
>
> Having the attribute ahead of "union" is, I think, strictly speaking
> undefined behavior, as it then may as well apply to "typedef".

No.  The result is

/local/xen.git/xen/include/asm/hvm/vmx/vmx.h:605:40: error: expected
identifier or '('
typedef union ept_qual __transparent__ {
                                       ^
/local/xen.git/xen/include/asm/hvm/vmx/vmx.h:614:3: error: type
specifier missing, defaults to 'int' [-Werror,-Wimplicit-int]
} ept_qual_t;
  ^~~~~~~~~~
2 errors generated.

In which case the original patch as proposed will probably do.  It turns
out the presence of ept_qual_t does cause a compiler error if
__transparent__ is missing from scope.

~Andrew

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