> -----Original Message-----
> From: David Marchand <david.march...@redhat.com>
> Sent: Monday 23 June 2025 14:53
> To: dev@dpdk.org
> Cc: sta...@dpdk.org; Bruce Richardson <bruce.richard...@intel.com>; Tyler
> Retzlaff <roret...@linux.microsoft.com>; Neil Horman
> <nhor...@tuxdriver.com>
> Subject: [PATCH v2 07/10] tailq: fix cast macro for null pointer
>
> Doing arithmetics with the NULL pointer is undefined.
>
> Caught by UBSan:
>
> ../app/test/test_tailq.c:111:9: runtime error:
> member access within null pointer of type 'struct rte_tailq_head'
>
> Fixes: f6b4f6c9c123 ("tailq: use a single cast macro")
> Cc: sta...@dpdk.org
>
> Signed-off-by: David Marchand <david.march...@redhat.com>
> Acked-by: Bruce Richardson <bruce.richard...@intel.com>
> ---
> lib/eal/include/rte_tailq.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/lib/eal/include/rte_tailq.h b/lib/eal/include/rte_tailq.h
> index 89f7ef2134..c23df77d96 100644
> --- a/lib/eal/include/rte_tailq.h
> +++ b/lib/eal/include/rte_tailq.h
> @@ -54,7 +54,7 @@ struct rte_tailq_elem {
> * Return the first tailq entry cast to the right struct.
> */
> #define RTE_TAILQ_CAST(tailq_entry, struct_name) \
> - (struct struct_name *)&(tailq_entry)->tailq_head
> + (tailq_entry == NULL ? NULL : (struct struct_name *)&(tailq_entry)-
> >tailq_head)
>
> /**
> * Utility macro to make looking up a tailqueue for a particular struct
> easier.
First tailq_entry is missing parentheses. Also, it is worrying that we now use
macro argument twice. E.g. RTE_TAILQ_LOOKUP may become twice slower as a result.
Could we perhaps simplify the macro to `(struct struct_name *)(tailq_entry)`. I
tried to find or understand the reasons behind the original construction, but
could not.
