[vtk-developers] CLang woes with VTK5.8.0

[David Partyka]

Thank you for your patch and explanation. I queued this up with all the
patches I hope to apply for vtk 5.8.1.

On Fri, Dec 30, 2011 at 10:30 AM, kent williams
<nkwmailinglists at gmail.com>wrote:

> I've been trying to build VTK & ITK with CLang as part of another
> project, and run into a collision between two things CLang has a
> problem with:
>
> 1. vnl_math.h has a large number of warnings because of in-class
> definitions of static const float members.
> 2. vtkYoungsMaterialInterface.cxx has a macro ALLOC_LOCAL_ARRAY that
> uses a Gnu C extenstion to define arrays with variable length.
>
> To try and address #1, I add -Werror=gnu to the CLang compiler flags.
> If this is set, the compiler test for in-line static const float
> members fails, which gets rid of the gazillion warnings everywhere
> vnl_math.h is included.
>
> But this causes another problem (see #2) because
> vtkYoungsMaterialInterface.cxx no longer compiles, as -Werror=gnu
> makes all gnu extensions an error.
>
> The real problem is that CLang defines __GNUC__ -- I would think that
> if you make all the GNUC extensions errors, it would be a good idea of
> CLang no longer defined __GNUC__.
>
> Looking at the ALLOC_LOCAL_ARRAY macros, it looks like a simple patch
> would fix things:
>
> diff --git a/Graphics/vtkYoungsMaterialInterface.cxx
> b/Graphics/vtkYoungsMaterialInterface.cxx
> index a509a2b..407a83c 100644
> --- a/Graphics/vtkYoungsMaterialInterface.cxx
> +++ b/Graphics/vtkYoungsMaterialInterface.cxx
> @@ -2049,7 +2049,7 @@ namespace vtkYoungsMaterialInterfaceCellCutInternals
>   sdata += ROUND_SIZE( sizeof(type)*(n) )
>  #define FREE_LOCAL_ARRAY(name,type,n) sdata -= ROUND_SIZE(
> sizeof(type)*(n) )
>
> -#elif defined(__GNUC__) // Warning, this is a gcc extension, not all
> compiler accept it
> +#elif defined(__GNUC__) && !defined(__clang__) // Warning, this is a
> gcc extension, not all compiler accept it
>  #define ALLOC_LOCAL_ARRAY(name,type,n) type name[(n)]
>  #define FREE_LOCAL_ARRAY(name,type,n)
>  #else
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