[Mesa-dev] [PATCH] mesa: simplify detection of fpclassify

[Ian Romanick]

On 01/17/2015 07:10 AM, Felix Janda wrote:
> Fixes compilation with musl libc.
> ---
>  src/mesa/main/querymatrix.c | 16 +++++-----------
>  1 file changed, 5 insertions(+), 11 deletions(-)
> 
> diff --git a/src/mesa/main/querymatrix.c b/src/mesa/main/querymatrix.c
> index eb36c76..57c536f 100644
> --- a/src/mesa/main/querymatrix.c
> +++ b/src/mesa/main/querymatrix.c
> @@ -37,8 +37,10 @@
>  #define INT_TO_FIXED(x) ((GLfixed) ((x) << 16))
>  #define FLOAT_TO_FIXED(x) ((GLfixed) ((x) * 65536.0))
>  
> -#if defined(_MSC_VER)
> -#if _MSC_VER < 1800  /* Not required on VS2013 and above. */
> +#if defined(fpclassify)
> +/* fpclassify is available. */

At first I thought, "This is hinky because it assumes that fpclassify
is a #define."  After that I looked up the documentation of fpclassify,
and I found, "ISO C99 defines macros that let you determine what sort
of floating-point number a variable holds."

Could we change the comment here to be:

/* ISO C99 says that fpclassify is a macro.  Assume that any implementation
 * of fpclassify, whether it's in a C99 compiler or not, will be a macro.
 */

That way the next person doesn't have to do the same research.

With that change, the patch is

Reviewed-by: Ian Romanick <ian.d.romanick at intel.com>

> +#elif defined(_MSC_VER)
> +/* Not required on VS2013 and above. */
>  /* Oddly, the fpclassify() function doesn't exist in such a form
>   * on MSVC.  This is an implementation using slightly different
>   * lower-level Windows functions.
> @@ -71,16 +73,8 @@ fpclassify(double x)
>              return FP_NAN;
>      }
>  }
> -#endif  /* _MSC_VER < 1800 */
> -
> -#elif defined(__APPLE__) || defined(__CYGWIN__) || defined(__FreeBSD__) || \
> -     defined(__OpenBSD__) || defined(__NetBSD__) || defined(__DragonFly__) || \
> -     (defined(__sun) && defined(__C99FEATURES__)) || defined(__MINGW32__) || \
> -     (defined(__sun) && defined(__GNUC__)) || defined(ANDROID) || defined(__HAIKU__)
> -
> -/* fpclassify is available. */
>  
> -#elif !defined(_XOPEN_SOURCE) || _XOPEN_SOURCE < 600
> +#else
>  
>  enum {FP_NAN, FP_INFINITE, FP_ZERO, FP_SUBNORMAL, FP_NORMAL}
>  fpclassify(double x)
>