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

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 09/02/17 14:20, Jan Beulich wrote:
>>>> On 09.02.17 at 14:42, <andrew.cooper3@xxxxxxxxxx> wrote:
>> On 09/02/17 13:14, Jan Beulich wrote:
>>>>>> On 09.02.17 at 14:05, <andrew.cooper3@xxxxxxxxxx> wrote:
>>>> 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.
>>> But then the question is what the attribute applies to in the original
>>> version - the union, or just the typedef? The placement would
>>> suggest the latter, so I'd again be afraid of undefined behavior. Can
>>> it be moved ahead on that line?
>> You mean this?
>>
>> } __transparent__ ept_qual_t;
> Yes.
>
>> Clang is happy with that.
> Good.

Ok.  Fixed up and pushed.

~Andrew

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel