[PATCH v2] common/sfc: replace out of bounds condition with static_assert

[Ferruh Yigit]

On 1/19/2024 10:13 PM, Stephen Hemminger wrote:
> The sfc base code had its own definition of static assertions
> using the out of bound array access hack. Replace it with a
> static_assert like rte_common.h.
> 
> Fixes: f67e4719147d ("net/sfc/base: fix coding style")
> Signed-off-by: Stephen Hemminger <stephen at networkplumber.org>
> Acked-by: Morten Brørup <mb at smartsharesystems.com>
> ---
> v2 - add assert.h to make sure it works in other environments
> 
>  drivers/common/sfc_efx/base/efx.h | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/common/sfc_efx/base/efx.h b/drivers/common/sfc_efx/base/efx.h
> index 3312c2fa8f81..38f2aed3e336 100644
> --- a/drivers/common/sfc_efx/base/efx.h
> +++ b/drivers/common/sfc_efx/base/efx.h
> @@ -7,6 +7,8 @@
>  #ifndef	_SYS_EFX_H
>  #define	_SYS_EFX_H
>  
> +#include <assert.h>
> +
>  #include "efx_annote.h"
>  #include "efsys.h"
>  #include "efx_types.h"
> @@ -17,8 +19,8 @@
>  extern "C" {
>  #endif
>  
> -#define	EFX_STATIC_ASSERT(_cond)		\
> -	((void)sizeof (char[(_cond) ? 1 : -1]))
> +#define	EFX_STATIC_ASSERT(_cond) \
> +	do { static_assert((_cond), "assert failed" #_cond); } while (0)
>  
>  #define	EFX_ARRAY_SIZE(_array)			\
>  	(sizeof (_array) / sizeof ((_array)[0]))

Getting following build error with clang:

FAILED: drivers/common/sfc_efx/base/libsfc_base.a.p/ef10_filter.c.o

./drivers/common/sfc_efx/base/ef10_filter.c
../drivers/common/sfc_efx/base/ef10_filter.c:503:2: error: static_assert
expression is not an integral constant expression
        EFX_STATIC_ASSERT((EFX_FIELD_OFFSET(efx_filter_spec_t,
efs_outer_vid) %

^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../drivers/common/sfc_efx/base/efx.h:23:21: note: expanded from macro
'EFX_STATIC_ASSERT'
        do { static_assert((_cond), "assert failed" #_cond); } while (0)
                           ^~~~~~~
../drivers/common/sfc_efx/base/ef10_filter.c:503:21: note: cast that
performs the conversions of a reinterpret_cast is not allowed in a
constant expression
        EFX_STATIC_ASSERT((EFX_FIELD_OFFSET(efx_filter_spec_t,
efs_outer_vid) %
                           ^
../drivers/common/sfc_efx/base/efx.h:29:3: note: expanded from macro
'EFX_FIELD_OFFSET'
        ((size_t)&(((_type *)0)->_field))
         ^
../drivers/common/sfc_efx/base/ef10_filter.c:1246:18: error: shift count
>= width of type [-Werror,-Wshift-count-overflow]
        matches_count = MCDI_OUT_DWORD(req,
                        ^~~~~~~~~~~~~~~~~~~
../drivers/common/sfc_efx/base/efx_mcdi.h:493:2: note: expanded from
macro 'MCDI_OUT_DWORD'
        EFX_DWORD_FIELD(*MCDI_OUT2(_emr, efx_dword_t, _ofst),           \
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../drivers/common/sfc_efx/base/efx_types.h:533:30: note: expanded from
macro 'EFX_DWORD_FIELD'
            EFX_HIGH_BIT(_field)) & EFX_MASK32(_field))
                                    ^~~~~~~~~~~~~~~~~~
../drivers/common/sfc_efx/base/efx_types.h:145:23: note: expanded from
macro 'EFX_MASK32'
            (((((uint32_t)1) << EFX_WIDTH(_field))) - 1))
                             ^  ~~~~~~~~~~~~~~~~~
2 errors generated.