invalid type conversion error under windows + cuda

[faberno]

Hey,
when compiling cuda code with nanobind a invalid type conversion error is thrown in nanobind\nb_func.h
The error only occurs in Windows, in Linux it worked fine.

Did someone else encounter this problem or has a suggestion?

A minimal example that causes this error for me can be found here: https://github.com/lgarrison/cupy-nanobind-example
Below you find the source, CMakeLists and my console output with the error.

cuda.cu

#include <nanobind/nanobind.h>
#include <nanobind/ndarray.h>


namespace nb = nanobind;
using namespace nb::literals;


template <typename Scalar>
__global__ void double_arr_kernel(Scalar* out, const Scalar* in, size_t size) {
    size_t i = blockIdx.x * blockDim.x + threadIdx.x;
    if (i < size) {
        out[i] = 2 * in[i];
    }
}


template <typename Scalar>
void double_arr(nb::ndarray<Scalar, nb::ndim<1>, nb::device::cuda> outarr,
            nb::ndarray<const Scalar, nb::ndim<1>, nb::device::cuda> inarr) {

    size_t size = inarr.size();
    size_t block_size = 256;
    size_t num_blocks = (size + block_size - 1) / block_size;

    double_arr_kernel<<<num_blocks, block_size>>>(outarr.data(), inarr.data(), size);
}


NB_MODULE(cuda, m) {
    m.def("double_arr",
        &double_arr<float>,
        "outarr"_a.noconvert(),
        "inarr"_a.noconvert()
        );
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.15...3.27)
project(${SKBUILD_PROJECT_NAME} LANGUAGES CXX)

find_package(Python 3.8 COMPONENTS Interpreter Development.Module REQUIRED)
find_package(nanobind CONFIG REQUIRED)

enable_language(CUDA)

nanobind_add_module(cuda src/example/cuda.cu)

install(TARGETS cuda LIBRARY DESTINATION example)

Building wheels for collected packages: example
  Building wheel for example (pyproject.toml) ... error
  error: subprocess-exited-with-error
  
  × Building wheel for example (pyproject.toml) did not run successfully.
  │ exit code: 1
  ╰─> [92 lines of output]
      *** scikit-build-core 0.10.7 using CMake 3.30.3 (wheel)
      *** Configuring CMake...
      2024-09-24 12:35:58,560 - scikit_build_core - WARNING - Can't find a Python library, got libdir=None, ldlibrary=None, multiarch=None, masd=None
      loading initial cache file build\cp310-cp310-win_amd64\CMakeInit.txt
      -- Building for: Visual Studio 17 2022
      -- Selecting Windows SDK version 10.0.22621.0 to target Windows 10.0.22631.
      -- The CXX compiler identification is MSVC 19.40.33811.0
      -- Detecting CXX compiler ABI info
      -- Detecting CXX compiler ABI info - done
      -- Check for working CXX compiler: C:/Program Files (x86)/Microsoft Visual Studio/2022/BuildTools/VC/Tools/MSVC/14.40.33807/bin/Hostx64/x64/cl.exe - skipped
      -- Detecting CXX compile features
      -- Detecting CXX compile features - done
      -- Found Python: C:\Users\{user}\anaconda3\envs\cupy-nanobind-example\python.exe (found suitable version "3.10.14", minimum required is "3.8") found components: Interpreter Development.Module
      -- The CUDA compiler identification is NVIDIA 12.5.40
      -- Detecting CUDA compiler ABI info
      -- Detecting CUDA compiler ABI info - done
      -- Check for working CUDA compiler: C:/Program Files/NVIDIA GPU Computing Toolkit/CUDA/v12.5/bin/nvcc.exe - skipped
      -- Detecting CUDA compile features
      -- Detecting CUDA compile features - done
      -- Configuring done (4.1s)
      -- Generating done (0.1s)
      -- Build files have been written to: C:/Users/{user}/PycharmProjects/cupy-nanobind-example/build/cp310-cp310-win_amd64
      *** Building project with Visual Studio 17 2022...
      MSBuild version 17.10.4+10fbfbf2e for .NET Framework

        nanobind-static.vcxproj -> C:\Users\{user}\PycharmProjects\cupy-nanobind-example\build\cp310-cp310-win_amd64\Release\nanobind-static.lib
        Compiling CUDA source file ..\..\src\example\cuda.cu...

        C:\Users\{user}\PycharmProjects\cupy-nanobind-example\build\cp310-cp310-win_amd64>"C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v12.5\bin\nvcc.exe"  --use-local-env -ccbin "C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\VC\Tools\MSVC\14.40.33807\bin\HostX64\x64" -x cu   -I"C:\Us
ers\{user}\anaconda3\envs\cupy-nanobind-example\Lib\site-packages\nanobind\include" -I"C:\Users\{user}\anaconda3\envs\cupy-nanobind-example\Include" -I"C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v12.5\include"     --keep-dir cuda\x64\Release  -maxrregcount=0   --machine 64 --compile -cudart static -st
d=c++17 --generate-code=arch=compute_52,code=[compute_52,sm_52] -Xcompiler="/EHsc -Ob2"   -D_WINDOWS -DNDEBUG -D"CMAKE_INTDIR=\"Release\"" -Dcuda_EXPORTS -D_WINDLL -D_MBCS -DWIN32 -D_WINDOWS -DNDEBUG -D"CMAKE_INTDIR=\"Release\"" -Dcuda_EXPORTS -Xcompiler "/EHsc /W1 /nologo /O2 /FS   /MD " -Xcompiler "/Fdcuda.dir\Release\vc143.pdb" -o cuda.dir\Release\cuda.obj "C:\Users\{user}\PycharmProjects\cupy-nanobind-example\src\example\cuda.cu"
      C:\Users\{user}\anaconda3\envs\cupy-nanobind-example\Lib\site-packages\nanobind\include\nanobind\nb_error.h(30): warning #1388-D: base class dllexport/dllimport specification differs from that of the derived class [C:\Users\{user}\PycharmProjects\cupy-nanobind-example\build\cp310-cp310-win_amd64\cuda.vcxproj]
          class __declspec(dllexport) python_error : public std::exception {
                                                            ^

        Remark: The warnings can be suppressed with "-diag-suppress <warning-number>"

      C:\Users\{user}\anaconda3\envs\cupy-nanobind-example\Lib\site-packages\nanobind\include\nanobind\nb_error.h(98): warning #1388-D: base class dllexport/dllimport specification differs from that of the derived class [C:\Users\{user}\PycharmProjects\cupy-nanobind-example\build\cp310-cp310-win_amd64\cuda.vcxproj]
          class __declspec(dllexport) builtin_exception : public std::runtime_error {
                                                                 ^

      C:\Users\{user}\anaconda3\envs\cupy-nanobind-example\Lib\site-packages\nanobind\include\nanobind\nb_error.h(30): warning #1388-D: base class dllexport/dllimport specification differs from that of the derived class [C:\Users\{user}\PycharmProjects\cupy-nanobind-example\build\cp310-cp310-win_amd64\cuda.vcxproj]
          class __declspec(dllexport) python_error : public std::exception {
                                                            ^

        Remark: The warnings can be suppressed with "-diag-suppress <warning-number>"

      C:\Users\{user}\anaconda3\envs\cupy-nanobind-example\Lib\site-packages\nanobind\include\nanobind\nb_error.h(98): warning #1388-D: base class dllexport/dllimport specification differs from that of the derived class [C:\Users\{user}\PycharmProjects\cupy-nanobind-example\build\cp310-cp310-win_amd64\cuda.vcxproj]
          class __declspec(dllexport) builtin_exception : public std::runtime_error {
                                                                 ^

      C:\Users\{user}\anaconda3\envs\cupy-nanobind-example\Lib\site-packages\nanobind\include\nanobind\nb_func.h(212): error : invalid type conversion [C:\Users\{user}\PycharmProjects\cupy-nanobind-example\build\cp310-cp310-win_amd64\cuda.vcxproj]
                                 cap->func(static_cast<cast_t<Args>>(in.template get<Is>())...),
                                           ^
                  detected during:
                    instantiation of "PyObject *nanobind::detail::func_create<ReturnRef,CheckGuard,Func,Return,Args...,Is...,Extra...>(Func &&, Return (*)(Args...), std::index_sequence<Is...>, const Extra &...) [with ReturnRef=false, CheckGuard=true, Func=lambda [](nanobind::handle)->nanobind::object, Return=nanobind::object, Args=<nanobind::handle>, Is=<0ULL>, Extra=<nanobind::scope, nanobind::name>]" at line 292
                    instantiation of "void nanobind::cpp_function_def(Func &&, const Extra &...) [with <unnamed>=void, Func=lambda [](nanobind::handle)->nanobind::object, Extra=<nanobind::scope, nanobind::name>, <unnamed>=0]" at line 383 of C:\Users\{user}\anaconda3\envs\cupy-nanobind-example\Lib\site-packages\nanobind\include\nanobind\nb_class.h

      C:\Users\{user}\anaconda3\envs\cupy-nanobind-example\Lib\site-packages\nanobind\include\nanobind\nb_func.h(82): warning #177-D: variable "kwonly_pos_n" was declared but never referenced [C:\Users\{user}\PycharmProjects\cupy-nanobind-example\build\cp310-cp310-win_amd64\cuda.vcxproj]
                  kwonly_pos_n = index_n_v<std::is_same_v<kw_only, Extra>...>;
                  ^
                  detected during:
                    instantiation of "PyObject *nanobind::detail::func_create<ReturnRef,CheckGuard,Func,Return,Args...,Is...,Extra...>(Func &&, Return (*)(Args...), std::index_sequence<Is...>, const Extra &...) [with ReturnRef=false, CheckGuard=true, Func=lambda [](nanobind::handle)->nanobind::object, Return=nanobind::object, Args=<nanobind::handle>, Is=<0ULL>, Extra=<nanobind::scope, nanobind::name>]" at line 292
                    instantiation of "void nanobind::cpp_function_def(Func &&, const Extra &...) [with <unnamed>=void, Func=lambda [](nanobind::handle)->nanobind::object, Extra=<nanobind::scope, nanobind::name>, <unnamed>=0]" at line 383 of C:\Users\{user}\anaconda3\envs\cupy-nanobind-example\Lib\site-packages\nanobind\include\nanobind\nb_class.h

      C:\Users\{user}\anaconda3\envs\cupy-nanobind-example\Lib\site-packages\nanobind\include\nanobind\nb_func.h(203): error : invalid type conversion [C:\Users\{user}\PycharmProjects\cupy-nanobind-example\build\cp310-cp310-win_amd64\cuda.vcxproj]
                      cap->func(static_cast<cast_t<Args>>(in.template get<Is>())...);
                                ^
                  detected during:
                    instantiation of "PyObject *nanobind::detail::func_create<ReturnRef,CheckGuard,Func,Return,Args...,Is...,Extra...>(Func &&, Return (*)(Args...), std::index_sequence<Is...>, const Extra &...) [with ReturnRef=false, CheckGuard=true, Func=void (*&)(nanobind::ndarray<float, nanobind::shape<-
1LL>, nanobind::device::cuda>, nanobind::ndarray<const float, nanobind::shape<-1LL>, nanobind::device::cuda>), Return=void, Args=<nanobind::ndarray<float, nanobind::shape<-1LL>, nanobind::device::cuda>, nanobind::ndarray<const float, nanobind::shape<-1LL>, nanobind::device::cuda>>, Is=<0ULL, 1ULL>, Extra=<nanobind::scope, nanobind::name, nanobind::arg, nanobind::arg>]" at line 271
                    instantiation of "void nanobind::cpp_function_def(Return (*)(Args...), const Extra &...) [with <unnamed>=void, Return=void, Args=<nanobind::ndarray<float, nanobind::shape<-1LL>, nanobind::device::cuda>, nanobind::ndarray<const float, nanobind::shape<-1LL>, nanobind::device::cuda>>, Extra=<nanobind::scope, nanobind::name, nanobind::arg, nanobind::arg>]" at line 348
                    instantiation of "nanobind::module_ &nanobind::module_::def(const char *, Func &&, const Extra &...) [with Func=void (*)(nanobind::ndarray<float, nanobind::shape<-1LL>, nanobind::device::cuda>, nanobind::ndarray<const float, nanobind::shape<-1LL>, nanobind::device::cuda>), Extra=<nanobind::arg, nanobind::arg>]" at line 31 of C:\Users\{user}\PycharmProjects\cupy-nanobind-example\src\example\cuda.cu

      C:\Users\{user}\anaconda3\envs\cupy-nanobind-example\Lib\site-packages\nanobind\include\nanobind\nb_func.h(203): error : invalid type conversion [C:\Users\{user}\PycharmProjects\cupy-nanobind-example\build\cp310-cp310-win_amd64\cuda.vcxproj]
                      cap->func(static_cast<cast_t<Args>>(in.template get<Is>())...);
                                ^
                  detected during:
                    instantiation of "PyObject *nanobind::detail::func_create<ReturnRef,CheckGuard,Func,Return,Args...,Is...,Extra...>(Func &&, Return (*)(Args...), std::index_sequence<Is...>, const Extra &...) [with ReturnRef=false, CheckGuard=true, Func=void (*&)(nanobind::ndarray<float, nanobind::shape<-
1LL>, nanobind::device::cuda>, nanobind::ndarray<const float, nanobind::shape<-1LL>, nanobind::device::cuda>), Return=void, Args=<nanobind::ndarray<float, nanobind::shape<-1LL>, nanobind::device::cuda>, nanobind::ndarray<const float, nanobind::shape<-1LL>, nanobind::device::cuda>>, Is=<0ULL, 1ULL>, Extra=<nanobind::scope, nanobind::name, nanobind::arg, nanobind::arg>]" at line 271
                    instantiation of "void nanobind::cpp_function_def(Return (*)(Args...), const Extra &...) [with <unnamed>=void, Return=void, Args=<nanobind::ndarray<float, nanobind::shape<-1LL>, nanobind::device::cuda>, nanobind::ndarray<const float, nanobind::shape<-1LL>, nanobind::device::cuda>>, Extra=<nanobind::scope, nanobind::name, nanobind::arg, nanobind::arg>]" at line 348
                    instantiation of "nanobind::module_ &nanobind::module_::def(const char *, Func &&, const Extra &...) [with Func=void (*)(nanobind::ndarray<float, nanobind::shape<-1LL>, nanobind::device::cuda>, nanobind::ndarray<const float, nanobind::shape<-1LL>, nanobind::device::cuda>), Extra=<nanobind::arg, nanobind::arg>]" at line 31 of C:\Users\{user}\PycharmProjects\cupy-nanobind-example\src\example\cuda.cu

      C:\Users\{user}\anaconda3\envs\cupy-nanobind-example\Lib\site-packages\nanobind\include\nanobind\nb_func.h(82): warning #177-D: variable "kwonly_pos_n" was declared but never referenced [C:\Users\{user}\PycharmProjects\cupy-nanobind-example\build\cp310-cp310-win_amd64\cuda.vcxproj]
                  kwonly_pos_n = index_n_v<std::is_same_v<kw_only, Extra>...>;
                  ^
                  detected during:
                    instantiation of "PyObject *nanobind::detail::func_create<ReturnRef,CheckGuard,Func,Return,Args...,Is...,Extra...>(Func &&, Return (*)(Args...), std::index_sequence<Is...>, const Extra &...) [with ReturnRef=false, CheckGuard=true, Func=void (*&)(nanobind::ndarray<float, nanobind::shape<-
1LL>, nanobind::device::cuda>, nanobind::ndarray<const float, nanobind::shape<-1LL>, nanobind::device::cuda>), Return=void, Args=<nanobind::ndarray<float, nanobind::shape<-1LL>, nanobind::device::cuda>, nanobind::ndarray<const float, nanobind::shape<-1LL>, nanobind::device::cuda>>, Is=<0ULL, 1ULL>, Extra=<nanobind::scope, nanobind::name, nanobind::arg, nanobind::arg>]" at line 271
                    instantiation of "void nanobind::cpp_function_def(Return (*)(Args...), const Extra &...) [with <unnamed>=void, Return=void, Args=<nanobind::ndarray<float, nanobind::shape<-1LL>, nanobind::device::cuda>, nanobind::ndarray<const float, nanobind::shape<-1LL>, nanobind::device::cuda>>, Extra=<nanobind::scope, nanobind::name, nanobind::arg, nanobind::arg>]" at line 348
                    instantiation of "nanobind::module_ &nanobind::module_::def(const char *, Func &&, const Extra &...) [with Func=void (*)(nanobind::ndarray<float, nanobind::shape<-1LL>, nanobind::device::cuda>, nanobind::ndarray<const float, nanobind::shape<-1LL>, nanobind::device::cuda>), Extra=<nanobind::arg, nanobind::arg>]" at line 31 of C:\Users\{user}\PycharmProjects\cupy-nanobind-example\src\example\cuda.cu

        3 errors detected in the compilation of "C:/Users/{user}/PycharmProjects/cupy-nanobind-example/src/example/cuda.cu".
        cuda.cu
      C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\MSBuild\Microsoft\VC\v170\BuildCustomizations\CUDA 12.5.targets(799,9): error MSB3721: The command ""C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v12.5\bin\nvcc.exe"  --use-local-env -ccbin "C:\Program Files (x86)\Microsoft Visual St
udio\2022\BuildTools\VC\Tools\MSVC\14.40.33807\bin\HostX64\x64" -x cu   -I"C:\Users\{user}\anaconda3\envs\cupy-nanobind-example\Lib\site-packages\nanobind\include" -I"C:\Users\{user}\anaconda3\envs\cupy-nanobind-example\Include" -I"C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v12.5\include"     --keep-d
ir cuda\x64\Release  -maxrregcount=0   --machine 64 --compile -cudart static -std=c++17 --generate-code=arch=compute_52,code=[compute_52,sm_52] -Xcompiler="/EHsc -Ob2"   -D_WINDOWS -DNDEBUG -D"CMAKE_INTDIR=\"Release\"" -Dcuda_EXPORTS -D_WINDLL -D_MBCS -DWIN32 -D_WINDOWS -DNDEBUG -D"CMAKE_INTDIR=\"Release\""
 -Dcuda_EXPORTS -Xcompiler "/EHsc /W1 /nologo /O2 /FS   /MD " -Xcompiler "/Fdcuda.dir\Release\vc143.pdb" -o cuda.dir\Release\cuda.obj "C:\Users\{user}\PycharmProjects\cupy-nanobind-example\src\example\cuda.cu"" exited with code 1. [C:\Users\{user}\PycharmProjects\cupy-nanobind-example\build\cp310-cp310-win_amd64\cuda.vcxproj]

      *** CMake build failed
      [end of output]

  note: This error originates from a subprocess, and is likely not a problem with pip.
  ERROR: Failed building wheel for example
Failed to build example
ERROR: ERROR: Failed to build installable wheels for some pyproject.toml based projects (example)

[wjakob]

Should be fixed on master now.