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Re: [PATCH v2] misra: add deviation for MISRA C Rule 11.3
- To: Dmytro Prokopchuk1 <dmytro_prokopchuk1@xxxxxxxx>, Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Mon, 25 Aug 2025 12:23:18 +0200
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- Cc: Doug Goldstein <cardoe@xxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Julien Grall <julien@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Mon, 25 Aug 2025 10:23:28 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 24.08.2025 19:27, Dmytro Prokopchuk1 wrote:
> MISRA C Rule 11.3 states: "A cast shall not be performed between a pointer
> to object type and a pointer to a different object type."
>
> Violations of this rule arise due to the 'container_of()' macro, which casts
> a member of a structure to its containing structure:
> container_of(ptr, type, member) ({ \
> typeof_field(type, member) *__mptr = (ptr); \
> (type *)( (char *)__mptr - offsetof(type,member) );})
>
> The 'container_of()' macro is safe because it relies on the standardized and
> well-defined 'offsetof()' macro to calculate the memory address of the
> containing structure, while assuming proper alignment and ensuring no
> undefined behavior, provided that the input pointer is valid and points to
> the specified member.
I may have said so before: This all reads okay to me, just that I'm unsure
it would actually be convincing to an assessor. The "provided that ..." is
a pretty strong requirement, which isn't overly hard to get wrong. Stefano,
Nicola - what's your take here?
Jan
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