[Insight-users] Bug in itkBSplineInterpolationWeightFunction.txx

[itkuser at yahoo.fr]

I had already submitted this bug to the phpBugTracker a while ago, but it is 
still there...

Fast floor function BSplineFloor(double x) in file 
itkBSplineInterpolationWeightFunction.txx is not correct on x86 platform:
it casts an int pointer to a double pointer, which is forbidden by ISO C 
standard (standard says that two different pointers may not point to the same 
location, as a result when optimizing the BSplineFloor function, the 
dereferencement and assignement of the pointer to double is optimized away).

The bug can be reproduced using gcc 3.4 with -O2 or -O3 flag on x86 platform, 
with the simple test case:

inline int BSplineFloor(double x)
{
  unsigned int hilo[2];
  *((double *)hilo) = x + 103079215104.0;  // (2**(52-16))*1.5
  return (int)((hilo[1]<<16)|(hilo[0]>>16));
}

int main()
{
   assert(BSplineFloor(0.5)==0);   
   return 0;   
}

Replacing
  unsigned int hilo[2];
  *((double *)hilo) = x + 103079215104.0;
  return (int)((hilo[1]<<16)|(hilo[0]>>16));
by
  union { unsigned int hilo[2]; double d; } u;  
  u.d = x + 103079215104.0;
  return (int)((u.hilo[1]<<16)|(u.hilo[0]>>16));
seems to fix the problem.

Could this bug be fixed for the next release?

Thanks,
nicolas