netdev - Re: [RFC PATCH net-next v1 08/11] drivers/net/ethernet: handle one warning explicitly

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Message-ID: <401624a4-2fcf-53c9-fe8d-f4e5fb6d3fba@intel.com>
Date:   Fri, 11 Sep 2020 15:56:42 -0700
From:   Jacob Keller <jacob.e.keller@...el.com>
To:     Jesse Brandeburg <jesse.brandeburg@...el.com>,
        netdev@...r.kernel.org
Cc:     intel-wired-lan@...ts.osuosl.org
Subject: Re: [RFC PATCH net-next v1 08/11] drivers/net/ethernet: handle one
 warning explicitly



On 9/10/2020 6:23 PM, 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 #pragma.
> 
> Signed-off-by: Jesse Brandeburg <jesse.brandeburg@...el.com>
> ---
>  drivers/net/ethernet/renesas/sh_eth.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/net/ethernet/renesas/sh_eth.c b/drivers/net/ethernet/renesas/sh_eth.c
> index 586642c33d2b..659530f9c117 100644
> --- a/drivers/net/ethernet/renesas/sh_eth.c
> +++ b/drivers/net/ethernet/renesas/sh_eth.c
> @@ -45,6 +45,13 @@
>  #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
> + */
> +#pragma GCC diagnostic push
> +#pragma GCC diagnostic ignored "-Woverride-init"


This should probably use something like the __diag() macros instead of
GCC-specific code, e.g.

__diag_push()
__diag_ignore(GCC, <version>, "-Woverride-init")

...

__diag_pop()

Where <version> is the major GCC version that introduced this warning.

Thanks,
Jake

>  static const u16 sh_eth_offset_gigabit[SH_ETH_MAX_REGISTER_OFFSET] = {
>  	SH_ETH_OFFSET_DEFAULTS,
>  
> @@ -332,6 +339,7 @@ static const u16 sh_eth_offset_fast_sh3_sh2[SH_ETH_MAX_REGISTER_OFFSET] = {
>  
>  	[TSU_ADRH0]	= 0x0100,
>  };
> +#pragma GCC diagnostic pop
>  
>  static void sh_eth_rcv_snd_disable(struct net_device *ndev);
>  static struct net_device_stats *sh_eth_get_stats(struct net_device *ndev);
>