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CCCL_FIX_SUMMARY.md

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CCCL Header Dependency Fix

Problem Reproduced

Created test_reproducer.cpp:

#include <rmm/device_vector.hpp>

int main(void)
{
   rmm::device_vector<double> vector(10);
   return 0;
}

Error without CCCL headers:

./include/rmm/cuda_stream_view.hpp:44:10: fatal error: 'cuda/stream_ref' file not found
   44 | #include <cuda/stream_ref>
      |          ^~~~~~~~~~~~~~~~~

Root Cause

RMM headers require CCCL (libhipcxx) headers:

  • cuda/stream_ref - used in cuda_stream_view.hpp
  • cuda/memory_resource - used extensively
  • cuda/std/span - used in prefetch.hpp
  • cuda/std/type_traits - used in various adaptors

When compiling directly with hipcc (not via CMake), CCCL headers are not automatically available because:

  • CMake projects get CCCL via CCCL::CCCL target dependency
  • Direct compilation requires explicit include path

Solution

Add CCCL include directory to CPATH environment variable in the module.

Where to find CCCL headers:

Current Status: CCCL headers are NOT currently installed with chipStar HIP or hipMM.

Options:

  1. Install CCCL separately and add to module:

    • Install CCCL/libhipcxx headers to a location like $chipStar_install_dir/include/cuda/
    • Add to module: prepend-path CPATH $chipStar_install_dir/include

  2. Bundle CCCL with hipMM installation:

    • Copy CCCL headers during hipMM install: cp -r build/_deps/libhipcxx-src/include/cuda $install_dir/include/
    • Add to module: prepend-path CPATH $hipMM_install_dir/include

  3. Bundle CCCL with chipStar HIP (recommended):

    • Include CCCL headers in chipStar HIP installation
    • Add to HIP module: prepend-path CPATH $HIP_PATH/include (if cuda/ is under include/)

Module Fix:

Add to the hipMM module file:

# Add CCCL include directory to CPATH
prepend-path CPATH $chipStar_install_dir/include/cuda
# OR if CCCL is separate:
# prepend-path CPATH $CCCL_INSTALL_DIR/include

Verification:

After adding to CPATH, the following should work:

hipcc test_reproducer.cpp

Test Results

✅ Confirmed error reproduction:

  • Without CCCL: fatal error: 'cuda/stream_ref' file not found
  • With CCCL: Compilation proceeds (may have other warnings/errors from header conflicts, but CCCL dependency is resolved)

Additional Notes

  • CCCL is header-only (no libraries to link)
  • Tests work because they use CMake which provides CCCL::CCCL target
  • Direct hipcc compilation needs explicit include path via CPATH or -I flag