[vtk-developers] CLang woes with VTK5.8.0

[kent williams]

That ALLOC_LOCAL_ARRAY thing is clunky anyway.  The whole mess with
the ifdefs could be replaced by a simple template class which should
be just as efficient and more portable:

template <typename TArrayElement, unsigned TSize>
class AutoArray
{
public:
  TArrayElement & operator[] (const unsigned nIndex)
    {
      return m_Array[nIndex];
    }
private:
  TArrayElement m_Array[TSize];
};
#define ALLOC_LOCAL_ARRAY(name,type,n) AutoArray<type,n> name;



On Fri, Dec 30, 2011 at 9:35 AM, David Partyka
<david.partyka at kitware.com> wrote:
> 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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>