[Mesa-dev] [RFC v2 13/15] mesa/macros: add power-of-two assertions for ALIGN and ROUND_DOWN_TO

[Brian Paul]

On 06/01/2015 11:13 AM, Nanley Chery wrote:
> From: Nanley Chery <nanley.g.chery at intel.com>
>
> ALIGN and ROUND_DOWN_TO both require that the alignment value passed into the
> macro be a power of two in the comments. Using software assertions verifies
> this to be the case.
>
> Signed-off-by: Nanley Chery <nanley.g.chery at intel.com>
> ---
>   src/mesa/main/macros.h | 10 ++++++++--
>   1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/src/mesa/main/macros.h b/src/mesa/main/macros.h
> index c794da3..1348b08 100644
> --- a/src/mesa/main/macros.h
> +++ b/src/mesa/main/macros.h
> @@ -700,7 +700,10 @@ is_power_of_two(unsigned value)
>    *
>    * \sa ROUND_DOWN_TO()
>    */
> -#define ALIGN(value, alignment)  (((value) + (alignment) - 1) & ~((alignment) - 1))
> +#define ALIGN(value, alignment) ({                        \
> +      assert(is_power_of_two(alignment));                 \
> +      (((value) + (alignment) - 1) & ~((alignment) - 1)); \
> +   })
>

That construct will not compile with MSVC unfortunately (I just tested it).

-Brian

>   /**
>    * Align a value down to an alignment value
> @@ -713,7 +716,10 @@ is_power_of_two(unsigned value)
>    *
>    * \sa ALIGN()
>    */
> -#define ROUND_DOWN_TO(value, alignment) ((value) & ~(alignment - 1))
> +#define ROUND_DOWN_TO(value, alignment) ({                \
> +      assert(is_power_of_two(alignment));                 \
> +      ((value) & ~(alignment - 1));                       \
> +   })
>
>   /**
>    * Align a value up to an alignment value
>