netdev - RE: [PATCH net-next] eth: ice: silence the GCC 12 array-bounds warning

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Date:   Fri, 20 May 2022 12:58:35 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Jakub Kicinski' <kuba@...nel.org>,
        "davem@...emloft.net" <davem@...emloft.net>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "jesse.brandeburg@...el.com" <jesse.brandeburg@...el.com>,
        "anthony.l.nguyen@...el.com" <anthony.l.nguyen@...el.com>
Subject: RE: [PATCH net-next] eth: ice: silence the GCC 12 array-bounds
 warning

From: Jakub Kicinski
> Sent: 20 May 2022 07:09
> 
> GCC 12 gets upset because driver allocates partial
> struct ice_aqc_sw_rules_elem buffers. The writes are
> within bounds.
> 
> Silence these warnings for now, our build bot runs GCC 12
> so we won't allow any new instances.
> 
> Signed-off-by: Jakub Kicinski <kuba@...nel.org>
> ---
> CC: jesse.brandeburg@...el.com
> CC: anthony.l.nguyen@...el.com
> ---
>  drivers/net/ethernet/intel/ice/Makefile | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/net/ethernet/intel/ice/Makefile b/drivers/net/ethernet/intel/ice/Makefile
> index 9183d480b70b..588b6e8c7920 100644
> --- a/drivers/net/ethernet/intel/ice/Makefile
> +++ b/drivers/net/ethernet/intel/ice/Makefile
> @@ -47,3 +47,8 @@ ice-$(CONFIG_DCB) += ice_dcb.o ice_dcb_nl.o ice_dcb_lib.o
>  ice-$(CONFIG_RFS_ACCEL) += ice_arfs.o
>  ice-$(CONFIG_XDP_SOCKETS) += ice_xsk.o
>  ice-$(CONFIG_ICE_SWITCHDEV) += ice_eswitch.o
> +
> +# FIXME: temporarily silence -Warray-bounds on non W=1 builds
> +ifndef KBUILD_EXTRA_WARN
> +CFLAGS_ice_switch.o += $(call cc-disable-warning, array-bounds)
> +endif
> --
> 2.34.3

Is it possible to just add:

CFLAGS_ice_switch.o += $(disable-Warray-bounds)

and then ensure that disable-Warray-bounds is defined
(and expanded) by the time it is actually expanded?
This might be before or after the makefile is expanded.
But it would mean that the work is only done once.
I've an idea that 'call cc-disable-warning' is non-trivial.

	David

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