On Tue, Oct 20, 2026 at 08:49:44AM +0000, Morten Brørup wrote:
> On architectures where rte_memcpy() is defined as memcpy(),
> GCC warns about source/destination overflow when copying more than the
> source/destination size, even for code paths that are not taken in cases
> where the sizes are smaller.
>
> The relevant compiler warnings were disabled for GCC at the two
> occurrences, and comments describing the reason were added.
>
> NB:
> It has not been investigated which GCC versions are affected.
> GCC version 10 and up was chosen because that was what the previous
> versions of x86 rte_memcpy() disabled sligthly similar warnings for.
>
> PS:
> The alternative was to obfuscate the code, but that would make the code
> less readable, and might have unintended effects on architectures and
> compilers not suffering by this issue.
>
> Bugzilla ID: 2061
> Fixes: ee0822a0ef41 ("stack: introduce pile")
>
> The pile was introduce with this DPDK release, so no need to backport.
>
> Reported-by: Ali Alnubani <[email protected]>
> Signed-off-by: Morten Brørup <[email protected]>
> ---
> lib/stack/rte_stack_pile.h | 26 ++++++++++++++++++++++++++
> 1 file changed, 26 insertions(+)
>
> diff --git a/lib/stack/rte_stack_pile.h b/lib/stack/rte_stack_pile.h
> index 819bd1d47a..69aa0cbf88 100644
> --- a/lib/stack/rte_stack_pile.h
> +++ b/lib/stack/rte_stack_pile.h
> @@ -154,12 +154,25 @@ __rte_stack_pile_push(struct rte_stack *s,
> * Construct the bulk elements.
> * Copy bulks in reverse order, but ignore the object order within each
> bulk.
> */
> +#if defined(RTE_TOOLCHAIN_GCC) && (GCC_VERSION >= 100000)
> +/*
> + * On architectures where rte_memcpy() is defined as memcpy(),
> + * although GCC knows that this code path is not taken when the source's
> size is smaller than
> + * RTE_STACK_PILE_BULK_SIZE, it still warns about memcpy() source overread.
> + * So we disable the compiler warning for this memcpy() instance.
> + */
> +#pragma GCC diagnostic push
> +#pragma GCC diagnostic ignored "-Wstringop-overread"
> +#endif
> tmp = (struct rte_stack_lf_elem *)bulk_first;
> __rte_assume(n_bulk > 0);
> for (i = 0; i < n_bulk; i++, tmp = tmp->next)
> rte_memcpy(((struct rte_stack_pile_bulk_elem *)tmp)->objs,
> &obj_table[(n_bulk - i - 1) *
> RTE_STACK_PILE_BULK_SIZE],
> sizeof(void *) * RTE_STACK_PILE_BULK_SIZE);
An rte_assume before the memcpy asserting the sizes doesn't help?
> +#if defined(RTE_TOOLCHAIN_GCC) && (GCC_VERSION >= 100000)
> +#pragma GCC diagnostic pop
> +#endif
