On 30.04.2024 16:28, Nicola Vetrini wrote:
> MISRA C Rule 20.7 states: "Expressions resulting from the expansion
> of macro parameters shall be enclosed in parentheses". Therefore, some
> macro definitions should gain additional parentheses to ensure that all
> current and future users will be safe with respect to expansions that
> can possibly alter the semantics of the passed-in macro parameter.
>
> No functional change.
>
> Signed-off-by: Nicola Vetrini <nicola.vetr...@bugseng.com>
> ---
> Somewhat surprisingly, the change in the tools directory is also needed,
> otherwise
> some CI build jobs fail (see e.g. [1]). This is not undefined behaviour
> as long as the two definitions are kept in sync, following section
> 6.10.3p2 of the C99 standard, but having the definition in common-macros.h
> is still a potential problem.
>
> [1] https://gitlab.com/xen-project/people/bugseng/xen/-/jobs/6742878558
This is pretty absurd, and the use of the Xen header in
xg_dom_decompress_unsafe_zstd.c should probably have gone away with the
introduction of the unaligned macros into ...
> --- a/tools/include/xen-tools/common-macros.h
> +++ b/tools/include/xen-tools/common-macros.h
> @@ -102,7 +102,7 @@
>
> #define put_unaligned_t(type, val, ptr) do { \
> struct { type x; } __packed *ptr_ = (typeof(ptr_))(ptr); \
> - ptr_->x = val; \
> + ptr_->x = (val); \
> } while (0)
>
> #define get_unaligned(ptr) get_unaligned_t(typeof(*(ptr)), ptr)
... here. We simply cannot assume the two definitions can indefinitely
be kept in sync.
> --- a/xen/include/xen/unaligned.h
> +++ b/xen/include/xen/unaligned.h
> @@ -19,7 +19,7 @@
>
> #define put_unaligned_t(type, val, ptr) do { \
> struct { type x; } __packed *ptr_ = (typeof(ptr_))(ptr); \
> - ptr_->x = val; \
> + ptr_->x = (val);
> \
Nit: One of the padding tabs then wants dropping.
Jan
