Re: [dpdk-stable] [PATCH] build: disable gcc 10 zero-length-bounds warning

[David Marchand <david.marchand@redhat.com>]

On Thu, May 14, 2020 at 3:19 PM Kevin Traynor <ktraynor@redhat.com> wrote:
>
> gcc 10 issues warnings about the use of rearm_data marker
> from struct rte_mbuf.
>
> e.g.
> ../drivers/net/enic/enic_rxtx_vec_avx2.c: In function ‘rx_one’:
> ../drivers/net/enic/enic_rxtx_vec_avx2.c:21:2:
> warning:
> array subscript 0 is outside the bounds of an interior zero-length array
> ‘RTE_MARKER64’ {aka ‘long unsigned int[0]’} [-Wzero-length-bounds]
>    21 |  *(uint64_t *)&mb->rearm_data = enic->mbuf_initializer;
>       |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
> In file included from ../lib/librte_mbuf/rte_mbuf.h:45,
>                  from ../drivers/net/enic/enic_rxtx_vec_avx2.c:6:
> ../lib/librte_mbuf/rte_mbuf_core.h:484:15:
> note: while referencing ‘rearm_data’
>   484 |  RTE_MARKER64 rearm_data;
>       |
>
> Disable this warning for gcc 10 in order to allow v20.05 to build
> without changes to struct rte_mbuf.
>
> Bugzilla ID: 396
> Cc: stable@dpdk.org
>
> Signed-off-by: Kevin Traynor <ktraynor@redhat.com>
>
> ---
> Sending as per discussion at this mornings release meeting:
> http://inbox.dpdk.org/dev/2980eb50-124c-9da8-9927-0678081b652b@intel.com/
>
> Reference to Gavin's patch:
> http://inbox.dpdk.org/dev/CAJFAV8yL2GvEJtTXOLk6o0eXHi4CpZmqCoRsfN2WcDe_ju1C8A@mail.gmail.com/#t
> ---
>  config/meson.build           | 4 ++++
>  mk/toolchain/gcc/rte.vars.mk | 5 +++++
>  2 files changed, 9 insertions(+)
>
> diff --git a/config/meson.build b/config/meson.build
> index a1c38c053..43ab11310 100644
> --- a/config/meson.build
> +++ b/config/meson.build
> @@ -209,4 +209,8 @@ warning_flags = [
>         '-Wno-missing-field-initializers'
>  ]
> +if cc.get_id() == 'gcc' and cc.version().version_compare('>=10.0')
> +# FIXME: Bugzilla 396
> +       warning_flags += '-Wno-zero-length-bounds'
> +endif
>  if not dpdk_conf.get('RTE_ARCH_64')
>  # for 32-bit, don't warn about casting a 32-bit pointer to 64-bit int - it's fine!!
> diff --git a/mk/toolchain/gcc/rte.vars.mk b/mk/toolchain/gcc/rte.vars.mk
> index f19305e49..928f0e083 100644
> --- a/mk/toolchain/gcc/rte.vars.mk
> +++ b/mk/toolchain/gcc/rte.vars.mk
> @@ -82,4 +82,9 @@ WERROR_FLAGS += -Wno-uninitialized
>  endif
>
> +ifeq ($(shell test $(GCC_VERSION) -ge 100 && echo 1), 1)
> +# FIXME: Bugzilla 396
> +WERROR_FLAGS += -Wno-zero-length-bounds
> +endif
> +
>  HOST_WERROR_FLAGS := $(WERROR_FLAGS)
>
> --
> 2.21.3
>

Reviewed-by: David Marchand <david.marchand@redhat.com>


-- 
David Marchand