On Mon, 2020-09-14 at 18:44 -0700, Jesse Brandeburg wrote:
> While fixing the W=1 builds, this warning came up because the
> developers used a very tricky way to get structures initialized
> to a non-zero value, but this causes GCC to warn about an
> override. In this case the override was intentional, so just
> disable the warning for this code with a macro that results
> in disabling the warning for compiles on GCC versions after 8.
>
> NOTE: the __diag_ignore macro currently only accepts a second
> argument of 8 (version 80000)
>
> Signed-off-by: Jesse Brandeburg <jesse.brandeb...@intel.com>
> ---
> drivers/net/ethernet/renesas/sh_eth.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/drivers/net/ethernet/renesas/sh_eth.c
> b/drivers/net/ethernet/renesas/sh_eth.c
> index 586642c33d2b..c63304632935 100644
> --- a/drivers/net/ethernet/renesas/sh_eth.c
> +++ b/drivers/net/ethernet/renesas/sh_eth.c
> @@ -45,6 +45,15 @@
> #define SH_ETH_OFFSET_DEFAULTS \
> [0 ... SH_ETH_MAX_REGISTER_OFFSET - 1] = SH_ETH_OFFSET_INVALID
>
> +/* use some intentionally tricky logic here to initialize the whole
> struct to
> + * 0xffff, but then override certain fields, requiring us to
> indicate that we
> + * "know" that there are overrides in this structure, and we'll need
> to disable
> + * that warning from W=1 builds. GCC has supported this option since
> 4.2.X, but
> + * the macros available to do this only define GCC 8.
> + */
> +__diag_push();
> +__diag_ignore(GCC, 8, "-Woverride-init",
> + "logic to initialize all and then override some is OK");
> static const u16 sh_eth_offset_gigabit[SH_ETH_MAX_REGISTER_OFFSET] =
> {
> SH_ETH_OFFSET_DEFAULTS,
>
> @@ -332,6 +341,7 @@ static const u16
> sh_eth_offset_fast_sh3_sh2[SH_ETH_MAX_REGISTER_OFFSET] = {
>
> [TSU_ADRH0] = 0x0100,
> };
> +__diag_pop();
>
I don't have any strong feeling against disabling compiler warnings,
but maybe the right thing to do here is to initialize the gaps to the
invalid value instead of pre-initializing the whole thing first and
then setting up the valid values on the 2nd pass.
I don't think there are too many gaps to fill, it is doable, so maybe
add this as a comment to this driver maintainer so they could pickup
the work from here.
