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SubjectRe: [PATCH] chelsio: use BUG() instead of BUG_ON(1)
On Mon, Mar 25, 2019 at 5:49 AM Arnd Bergmann <arnd@arndb.de> wrote:
>
> clang warns about possible bugs in a dead code branch after
> BUG_ON(1) when CONFIG_PROFILE_ALL_BRANCHES is enabled:
>
> drivers/net/ethernet/chelsio/cxgb4/sge.c:479:3: error: variable 'buf_size' is used uninitialized whenever 'if'
> condition is false [-Werror,-Wsometimes-uninitialized]
> BUG_ON(1);
> ^~~~~~~~~
> include/asm-generic/bug.h:61:36: note: expanded from macro 'BUG_ON'
> #define BUG_ON(condition) do { if (unlikely(condition)) BUG(); } while (0)
> ^~~~~~~~~~~~~~~~~~~
> include/linux/compiler.h:48:23: note: expanded from macro 'unlikely'
> # define unlikely(x) (__branch_check__(x, 0, __builtin_constant_p(x)))
> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/net/ethernet/chelsio/cxgb4/sge.c:482:9: note: uninitialized use occurs here
> return buf_size;
> ^~~~~~~~
> drivers/net/ethernet/chelsio/cxgb4/sge.c:479:3: note: remove the 'if' if its condition is always true
> BUG_ON(1);
> ^
> include/asm-generic/bug.h:61:32: note: expanded from macro 'BUG_ON'
> #define BUG_ON(condition) do { if (unlikely(condition)) BUG(); } while (0)
> ^
> drivers/net/ethernet/chelsio/cxgb4/sge.c:459:14: note: initialize the variable 'buf_size' to silence this warning
> int buf_size;
> ^
> = 0
>
> Use BUG() here to create simpler code that clang understands
> correctly.

This is more concise and better expresses what we want to do here.
Thanks for the patch.
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> drivers/net/ethernet/chelsio/cxgb4/cxgb4_debugfs.c | 2 +-
> drivers/net/ethernet/chelsio/cxgb4/sge.c | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/ethernet/chelsio/cxgb4/cxgb4_debugfs.c b/drivers/net/ethernet/chelsio/cxgb4/cxgb4_debugfs.c
> index 3130b43bba52..02959035ed3f 100644
> --- a/drivers/net/ethernet/chelsio/cxgb4/cxgb4_debugfs.c
> +++ b/drivers/net/ethernet/chelsio/cxgb4/cxgb4_debugfs.c
> @@ -2620,7 +2620,7 @@ static inline struct port_info *ethqset2pinfo(struct adapter *adap, int qset)
> }
>
> /* should never happen! */
> - BUG_ON(1);
> + BUG();
> return NULL;
> }
>
> diff --git a/drivers/net/ethernet/chelsio/cxgb4/sge.c b/drivers/net/ethernet/chelsio/cxgb4/sge.c
> index 88773ca58e6b..b3da81e90132 100644
> --- a/drivers/net/ethernet/chelsio/cxgb4/sge.c
> +++ b/drivers/net/ethernet/chelsio/cxgb4/sge.c
> @@ -476,7 +476,7 @@ static inline int get_buf_size(struct adapter *adapter,
> break;
>
> default:
> - BUG_ON(1);
> + BUG();
> }
>
> return buf_size;
> --
> 2.20.0
>


--
Thanks,
~Nick Desaulniers

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