Build NanoVDB CUDA with clang

[lanwatch]

I just tried to do it and found several interesting warnings and errors that seem correctly reported but NVCC is overlooking.

I wonder if anybody else has tried this before. I think it's useful to improve code quality.

FWIW a patch along these lines is needed in order to build:

diff --git a/nanovdb/nanovdb/CMakeLists.txt b/nanovdb/nanovdb/CMakeLists.txt
index 4e0284ec..a005a0d4 100644
--- a/nanovdb/nanovdb/CMakeLists.txt
+++ b/nanovdb/nanovdb/CMakeLists.txt
@@ -88,12 +88,17 @@ if(NANOVDB_USE_CUDA)
 
   enable_language(CUDA)
 
-  set(NANOVDB_CUDA_EXTENDED_LAMBDA "--expt-extended-lambda")
-  if(CUDA_VERSION_MAJOR GREATER_EQUAL 11)
-    set(NANOVDB_CUDA_EXTENDED_LAMBDA "--extended-lambda")
+  if(CMAKE_CUDA_COMPILER_ID MATCHES "NVIDIA")
+    set(NANOVDB_CUDA_EXTENDED_LAMBDA "--expt-extended-lambda")
+    if(CUDA_VERSION_MAJOR GREATER_EQUAL 11)
+      set(NANOVDB_CUDA_EXTENDED_LAMBDA "--extended-lambda")
+    endif()
+    set(CMAKE_CUDA_FLAGS "${NANOVDB_CUDA_EXTENDED_LAMBDA} -use_fast_math -lineinfo ${CMAKE_CUDA_FLAGS}")
+  else()
+    set(CMAKE_CUDA_FLAGS "-ffast-math ${CMAKE_CUDA_FLAGS}")
+
   endif()
 
-  set(CMAKE_CUDA_FLAGS "${NANOVDB_CUDA_EXTENDED_LAMBDA} -use_fast_math -lineinfo ${CMAKE_CUDA_FLAGS}")
 
   # workaround for win32 bug when nvcc "--keep" is used.
   if(WIN32)

Afterwards just pass -DCMAKE_CUDA_COMPILER=clang++ along with the rest of options and clang++ will be used for CUDA code.

[lanwatch]

In case anyone is interested, I managed to compile and run tests with these changes:
58724e5...lanwatch:openvdb:master

Only one test fails:

[ RUN      ] TestNanoVDBCUDA.Random_CudaPointsToGrid_World64
CUDA error 715: an illegal instruction was encountered (/home/lanwatch/nvme/lanwatch/devel/openvdb/nanovdb/nanovdb/../nanovdb/tools/cuda/PointsToGrid.cuh:669)
<end of output>
Test time =   1.80 sec
----------------------------------------------------------
Test Failed.
"nanovdb_cuda_unit_test" end time: Nov 18 12:04 CET
"nanovdb_cuda_unit_test" time elapsed: 00:00:01
----------------------------------------------------------

3/3 Testing: nanovdb_openvdb_unit_test
3/3 Test: nanovdb_openvdb_unit_test
Command: "/home/lanwatch/nvme/lanwatch/devel/openvdb/build-clang/nanovdb/nanovdb/unittest/nanovdb_test_openvdb"
Directory: /home/lanwatch/nvme/lanwatch/devel/openvdb/build-clang/nanovdb/nanovdb/unittest
"nanovdb_openvdb_unit_test" start time: Nov 18 12:04 CET
Output:
----------------------------------------------------------