Re: struct mctelem_cookie missing definition

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 13/02/2025 1:25 am, Stefano Stabellini wrote:
> Hi all,
>
> I am looking through the few remaining MISRA violations that we have
> left.  One of them is R11.2:
>
> https://saas.eclairit.com:3787/fs/var/local/eclair/xen-project.ecdf/xen-project/hardware/xen/ECLAIR_normal/staging/X86_64/9118578464/PROJECT.ecd;/by_service/MC3A2.R11.2.html#{%22select%22:true,%22selection%22:{%22hiddenAreaKinds%22:[],%22hiddenSubareaKinds%22:[],%22show%22:false,%22selector%22:{%22enabled%22:true,%22negated%22:true,%22kind%22:0,%22domain%22:%22kind%22,%22inputs%22:[{%22enabled%22:true,%22text%22:%22violation%22}]}}}
>
> Specifically, mctelem_cookie_t is a pointer to incomplete type and
> therefore COOKIE2MCTE triggers a "conversion between a pointer to an
> incomplete type and any other type".
>
> mctelem_cookie_t is defined as:
>
> typedef struct mctelem_cookie *mctelem_cookie_t;
>
> I am looking through the code and I genuinely cannot find the definition
> of struct mctelem_cookie.
>
> If mctelem_cookie_t is only used as a pointer, wouldn't it make more
> sense to do:
>
> typedef struct mctelem_ent *mctelem_cookie_t;
>
> ?
>
> What am I missing?

Nothing.  Or perhaps the twisted thinking of the original author.

It is genuinely a pointer type (== known size) which you can't deference
(because there is no definition), and can only operate on by casting to
an integer.  Except the code also requires it to be a uint64_t which is
why there's some fun disabling of relevant hypercalls for compat guests.

If someone could find the time to file it in /dev/null and replace it
with literally anything else, I'd be very thankful.

~Andrew