[Mesa-dev] [PATCH] Avoid spurious GCC warnings in STATIC_ASSERT() macro.

[Brian Paul]

On 04/02/2013 04:16 PM, Paul Berry wrote:
> GCC 4.8 now warns about typedefs that are local to a scope and not
> used anywhere within that scope.  This produces spurious warnings with
> the STATIC_ASSERT() macro (which uses a typedef to provoke a compile
> error in the event of an assertion failure).
>
> This patch avoids the warning using the GCC __attribute__((unused))
> syntax.
> ---
>   src/mesa/main/compiler.h | 8 +++++++-
>   1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/src/mesa/main/compiler.h b/src/mesa/main/compiler.h
> index 8b23665..ddeb61d 100644
> --- a/src/mesa/main/compiler.h
> +++ b/src/mesa/main/compiler.h
> @@ -249,6 +249,12 @@ static INLINE GLuint CPU_TO_LE32(GLuint x)
>   #endif
>
>
> +#if (__GNUC__>= 3)
> +#define GCC_ATTRIBUTE_UNUSED __attribute__((unused))
> +#else
> +#define GCC_ATTRIBUTE_UNUSED
> +#endif
> +
>   /**
>    * Static (compile-time) assertion.
>    * Basically, use COND to dimension an array.  If COND is false/zero the
> @@ -256,7 +262,7 @@ static INLINE GLuint CPU_TO_LE32(GLuint x)
>    */
>   #define STATIC_ASSERT(COND) \
>      do { \
> -      typedef int static_assertion_failed[(!!(COND))*2-1]; \
> +      typedef int static_assertion_failed[(!!(COND))*2-1] GCC_ATTRIBUTE_UNUSED; \
>      } while (0)
>
>

Without using gcc-isms, I think this would work too:

#define STATIC_ASSERT(COND) \
    do { \
       int static_assertion_failed[(!!(COND))*2-1]; \
       (void) static_assertion_failed; \
    } while (0)

I don't recall why I used the typedef.

Also, the same macro should probably be updated in 
src/gallium/include/pipe/p_compiler.h

-Brian