2019-03-25 12:45:22

by Arnd Bergmann

Subject: [PATCH] wireless: carl9170: fix clang build warning

clang fails to eliminate some dead code with always-taken branches
when CONFIG_PROFILE_ANNOTATED_BRANCHES is set, leading to a false-positive
warning:

drivers/net/wireless/ath/carl9170/mac.c:522:3: error: variable 'power' is used uninitialized whenever 'if' condition is
false [-Werror,-Wsometimes-uninitialized]
BUG_ON(1);
^~~~~~~~~

Change both instances of BUG_ON(1) in carl9170 to the simpler BUG()
to avoid the warning.

Signed-off-by: Arnd Bergmann <[email protected]>
---
drivers/net/wireless/ath/carl9170/mac.c | 2 +-
drivers/net/wireless/ath/carl9170/rx.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/ath/carl9170/mac.c b/drivers/net/wireless/ath/carl9170/mac.c
index 7d4a72dc98db..b2eeb9fd68d2 100644
--- a/drivers/net/wireless/ath/carl9170/mac.c
+++ b/drivers/net/wireless/ath/carl9170/mac.c
@@ -519,7 +519,7 @@ int carl9170_set_mac_tpc(struct ar9170 *ar, struct ieee80211_channel *channel)
power = ar->power_5G_leg[0] & 0x3f;
break;
default:
- BUG_ON(1);
+ BUG();
}

power = min_t(unsigned int, power, ar->hw->conf.power_level * 2);
diff --git a/drivers/net/wireless/ath/carl9170/rx.c b/drivers/net/wireless/ath/carl9170/rx.c
index 8e154f6364a3..23ab8a80c18c 100644
--- a/drivers/net/wireless/ath/carl9170/rx.c
+++ b/drivers/net/wireless/ath/carl9170/rx.c
@@ -795,7 +795,7 @@ static void carl9170_rx_untie_data(struct ar9170 *ar, u8 *buf, int len)
break;

default:
- BUG_ON(1);
+ BUG();
break;
}

--
2.20.0

2019-03-25 14:21:12

by Christian Lamparter

Subject: Re: [PATCH] wireless: carl9170: fix clang build warning

On Monday, March 25, 2019 1:43:44 PM CET Arnd Bergmann wrote:
> clang fails to eliminate some dead code with always-taken branches
> when CONFIG_PROFILE_ANNOTATED_BRANCHES is set, leading to a false-positive
> warning:
>
> drivers/net/wireless/ath/carl9170/mac.c:522:3: error: variable 'power' is used uninitialized whenever 'if' condition is
> false [-Werror,-Wsometimes-uninitialized]
> BUG_ON(1);
> ^~~~~~~~~
>
> Change both instances of BUG_ON(1) in carl9170 to the simpler BUG()
> to avoid the warning.
>
> Signed-off-by: Arnd Bergmann <[email protected]>
Heh, I added these "default:" cases back in the day to make gcc
shut-up about "switch is missing cases" warnings. And now I
guess it's clangs time to complain. (-;

Especially the "default case" in carl9170_rx_untie_data is hilarious.
Since all the possible cases (just 4!) have been addressed and the
"default" is deadcode. I think gcc did not consider the
AR9170_RX_STATUS_MPDU mask in the
| switch (mac_status & AR9170_RX_STATUS_MPDU) {

statement. However I'll be waiting for the day until the deadcode
elimination warnings will show up.

Anyway,

Acked-by: Christian Lamparter <[email protected]>

Regards,
Christian

> ---
> drivers/net/wireless/ath/carl9170/mac.c | 2 +-
> drivers/net/wireless/ath/carl9170/rx.c | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/wireless/ath/carl9170/mac.c b/drivers/net/wireless/ath/carl9170/mac.c
> index 7d4a72dc98db..b2eeb9fd68d2 100644
> --- a/drivers/net/wireless/ath/carl9170/mac.c
> +++ b/drivers/net/wireless/ath/carl9170/mac.c
> @@ -519,7 +519,7 @@ int carl9170_set_mac_tpc(struct ar9170 *ar, struct ieee80211_channel *channel)
> power = ar->power_5G_leg[0] & 0x3f;
> break;
> default:
> - BUG_ON(1);
> + BUG();
> }
>
> power = min_t(unsigned int, power, ar->hw->conf.power_level * 2);
> diff --git a/drivers/net/wireless/ath/carl9170/rx.c b/drivers/net/wireless/ath/carl9170/rx.c
> index 8e154f6364a3..23ab8a80c18c 100644
> --- a/drivers/net/wireless/ath/carl9170/rx.c
> +++ b/drivers/net/wireless/ath/carl9170/rx.c
> @@ -795,7 +795,7 @@ static void carl9170_rx_untie_data(struct ar9170 *ar, u8 *buf, int len)
> break;
>
> default:
> - BUG_ON(1);
> + BUG();
> break;
> }
>
>