Mismatch between sizeof(Partio::ParticleIndex), sizeof(size_t), sizeof(int)

[StefanBruens]

There is some assumption Partio uses size_t for its index type:

OpenShadingLanguage/src/liboslexec/pointcloud.cpp

Lines 360 to 365 in 7e34ce2

 // RS::pointcloud_search takes size_t index array (because of the 
 // presumed use of Partio underneath), but OSL only has int, so we 
 // have to allocate and copy out.  But, on architectures where int 
 // and size_t are the same, we can take a shortcut and let 
 // pointcloud_search fill in the array in place (assuming it's 
 // passed in the first place). 

which is apparently wrong (for the last 12 years):
https://github.com/wdas/partio/blob/7cb3743c6e19c04ac049c05f8f81af2f24410ea3/src/lib/Partio.h#L55
typedef uint64_t ParticleIndex;

On 32 bit archs the compilation then fails due to:

OpenShadingLanguage/src/liboslexec/pointcloud.cpp

Lines 114 to 118 in 7e34ce2

 static_assert (sizeof(size_t) == sizeof(Partio::ParticleIndex), 
                "Partio ParticleIndex should be the size of a size_t"); 
 // FIXME -- if anybody cares about an architecture in which that is not 
 // the case, we can easily allocate local space to retrieve the indices, 
 // then copy them back to the caller's indices. 

Wouldn't it be better change it to unsigned long* out_indices in RendererServices::pointcloud_search? (This may require a version bump for 64bit archs, but only if size_t != unsigned long. For 32bit archs, the current code does not work anyway). Dito for pointcloud_get.