Re: [XEN PATCH v2 2/7] x86: add deviations for variables only used in asm code

[Nicola Vetrini <nicola.vetrini@bugseng.com>]

On 18/10/2023 16:56, Jan Beulich wrote:
> On 18.10.2023 16:28, Nicola Vetrini wrote:
>> On 16/10/2023 16:58, Jan Beulich wrote:
>>> On 09.10.2023 08:54, Nicola Vetrini wrote:
>>>> These variables are only used by asm code, and therefore
>>>> the lack of a declaration is justified by the corresponding
>>>> deviation comment.
>>> 
>>> Hmm, you say "declaration" here, but according to my understanding 
>>> ...
>>> 
>>>> --- a/xen/arch/x86/include/asm/asm_defns.h
>>>> +++ b/xen/arch/x86/include/asm/asm_defns.h
>>>> @@ -31,6 +31,7 @@ asm ( "\t.equ CONFIG_INDIRECT_THUNK, "
>>>>   * gets set up by the containing function.
>>>>   */
>>>>  #ifdef CONFIG_FRAME_POINTER
>>>> +/* SAF-1-safe */
>>>>  register unsigned long current_stack_pointer asm("rsp");
>>> 
>>> ... this is a declaration, not a definition.
>>> 
>> 
>> It has automatic storage duration and it's not defined afterwards
> 
> Mind me asking what makes you derive "automatic storage duration"?
> I also don't see how "not defined afterwards" matters here. This is
> a special construct, not covered by the C standard.
> 
> Jan

Oh, you're right. I was fooled by the fact that this is not a standard 
construct.
I see your point now.

Thanks,

-- 
Nicola Vetrini, BSc
Software Engineer, BUGSENG srl (https://bugseng.com)