On 9 Feb 2026, at 14:29, Eli Britstein wrote:
> From: Gaetan Rivet <[email protected]>
>
> Implicit padding bytes in a struct are not necessarily initialized.
> Comparing such struct with memcmp might be wrong. To verify correctness
> of such comparison, add a macro to statically assert whether a structure
> contains padding.
Thanks for the patch, Gaetan. Some small nits below.
//Eelco
> Signed-off-by: Gaetan Rivet <[email protected]>
> Co-authored-by: Eli Britstein <[email protected]>
> Signed-off-by: Eli Britstein <[email protected]>
> ---
> include/openvswitch/compiler.h | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/include/openvswitch/compiler.h b/include/openvswitch/compiler.h
> index 7dee9ec7a..961339944 100644
> --- a/include/openvswitch/compiler.h
> +++ b/include/openvswitch/compiler.h
> @@ -218,6 +218,18 @@
> #define OVS_PACKED(DECL) __pragma(pack(push, 1)) DECL __pragma(pack(pop))
> #endif
>
> +/* Define a type with this macro to enforce during
> + * compilation that it has no padding, i.e. packed.
> + * It *DOES NOT* pack the type, only statically check
> + * that it is already. Either the layout must be
We use double spaces after the end of sentences.
> + * made to fit, or explicit padding must be used.
> + */
I would personally add the comment ending on the same line. We seem to have
mixed ways of doing this in this file, but when reviewing I'm trying to steer
toward ending on the same line, unless the entire file does it differently.
> +#define OVS_ASSERT_PACKED(TYPE, MEMBERS) \
Since this is a build assertion, consider naming it like the other
BUILD_ASSERT_*
macros at the end of this file. Perhaps move it to that section as well for
consistency?
> + TYPE { \
> + MEMBERS \
> + }; \
> + BUILD_ASSERT_DECL(sizeof(TYPE) == sizeof(OVS_PACKED(struct { MEMBERS })))
> +
> /* OVS_ALIGNED_STRUCT may be used to define a structure whose instances
> should
> * aligned on an N-byte boundary. This:
> * OVS_ALIGNED_STRUCT(64, mystruct) { ... };
> --
> 2.34.1
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