On Thu, Mar 7, 2019 at 10:00 AM Nathan Chancellor
<natechancel...@gmail.com> wrote:
>
> When building with -Wsometimes-uninitialized, Clang warns:
>
> drivers/net/ethernet/stmicro/stmmac/stmmac_main.c:495:3: warning: variable
> 'ns' is used uninitialized whenever 'if' condition is false
> [-Wsometimes-uninitialized]
> drivers/net/ethernet/stmicro/stmmac/stmmac_main.c:495:3: warning: variable
> 'ns' is used uninitialized whenever '&&' condition is false
> [-Wsometimes-uninitialized]
> drivers/net/ethernet/stmicro/stmmac/stmmac_main.c:532:3: warning: variable
> 'ns' is used uninitialized whenever 'if' condition is false
> [-Wsometimes-uninitialized]
> drivers/net/ethernet/stmicro/stmmac/stmmac_main.c:532:3: warning: variable
> 'ns' is used uninitialized whenever '&&' condition is false
> [-Wsometimes-uninitialized]
> drivers/net/ethernet/stmicro/stmmac/stmmac_main.c:741:3: warning: variable
> 'sec_inc' is used uninitialized whenever 'if' condition is false
> [-Wsometimes-uninitialized]
> drivers/net/ethernet/stmicro/stmmac/stmmac_main.c:741:3: warning: variable
> 'sec_inc' is used uninitialized whenever '&&' condition is false
> [-Wsometimes-uninitialized]
>
> Clang is concerned with the use of stmmac_do_void_callback (which
> stmmac_get_timestamp and stmmac_config_sub_second_increment wrap),
> as it may fail to initialize these values if the if condition was ever
> false (meaning the callbacks don't exist). It's not wrong because the
> callbacks (get_timestamp and config_sub_second_increment respectively)
> are the ones that initialize the variables. While it's unlikely that the
> callbacks are ever going to disappear and make that condition false, we
> can easily avoid this warning by zero initialize the variables.
>
> Link: https://github.com/ClangBuiltLinux/linux/issues/384
> Suggested-by: Nick Desaulniers <ndesaulni...@google.com>
> Reviewed-by: Nick Desaulniers <ndesaulni...@google.com>
V2 LGTM, thanks for resending.
> Signed-off-by: Nathan Chancellor <natechancel...@gmail.com>
> ---
>
> v1 -> v2:
>
> * Respect reverse Christmas tree variable ordering in
> stmmac_hwtstamp_set.
>
> drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index e2a13ec2e30b..97c5e1aad88f 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -480,7 +480,7 @@ static void stmmac_get_tx_hwtstamp(struct stmmac_priv
> *priv,
> struct dma_desc *p, struct sk_buff *skb)
> {
> struct skb_shared_hwtstamps shhwtstamp;
> - u64 ns;
> + u64 ns = 0;
>
> if (!priv->hwts_tx_en)
> return;
> @@ -519,7 +519,7 @@ static void stmmac_get_rx_hwtstamp(struct stmmac_priv
> *priv, struct dma_desc *p,
> {
> struct skb_shared_hwtstamps *shhwtstamp = NULL;
> struct dma_desc *desc = p;
> - u64 ns;
> + u64 ns = 0;
>
> if (!priv->hwts_rx_en)
> return;
> @@ -564,8 +564,8 @@ static int stmmac_hwtstamp_set(struct net_device *dev,
> struct ifreq *ifr)
> u32 snap_type_sel = 0;
> u32 ts_master_en = 0;
> u32 ts_event_en = 0;
> + u32 sec_inc = 0;
> u32 value = 0;
> - u32 sec_inc;
> bool xmac;
>
> xmac = priv->plat->has_gmac4 || priv->plat->has_xgmac;
> --
> 2.21.0
>
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--
Thanks,
~Nick Desaulniers
