Error linking against SYCL on Windows (for interfacing with oneMKL)

[tbesard]

I'm working on a C wrapper for oneMKL (for the purpose of using the library from Julia, where we only have a C FFI). The library can be found here: https://github.com/JuliaGPU/oneAPI.jl/tree/master/deps

I'm compiling this library on a Linux buildbot where I pull the necessary oneAPI 2024.0.0 packages from Conda, and link a shared library using my own simple CMake script that relies on the system Clang compiler (because from this cross-build environment I can't execute the Intel compiler):

add_library(oneapi_support SHARED files...)

target_link_libraries(oneapi_support
mkl_sycl
mkl_intel_ilp64
mkl_sequential
mkl_core
sycl
OpenCL
pi_level_zero
)

I'm redistributing the resulting shared library together with the libraries it needs. This works perfectly, on Linux.

I now want to do the same for native Windows. Now using a MinGW-based environment, I again pull the necessary win-64 packages from Conda, and try to build a shared library. For one, I have to adjust my list of target libraries as things seem to be named differently on Windows (is this expected?):

target_link_libraries(oneapi_support
mkl_sycl
mkl_intel_ilp64_dll
mkl_sequential.2
mkl_core.2
sycl7
OpenCL
pi_level_zero
)

However, even then I'm running into a linker error:

[1/1] Linking CXX shared library liboneapi_support.dll
ninja: job failed: : && /opt/bin/x86_64-w64-mingw32-libgfortran5-cxx11/x86_64-w64-mingw32-clang++ --sysroot=/opt/x86_64-w64-mingw32/x86_64-w64-mingw32/sys-root/ -O2 -g -DNDEBUG -L/workspace/destdir/bin -shared -o liboneapi_support.dll -Wl,--out-implib,liboneapi_support.dll.a -Wl,--major-image-version,0,--minor-image-version,0 CMakeFiles/oneapi_support.dir/src/sycl.cpp.obj CMakeFiles/oneapi_support.dir/src/onemkl.cpp.obj -lmkl_sycl -lmkl_intel_ilp64_dll -lmkl_sequential.2 -lmkl_core.2 -lsycl7 -lOpenCL -lpi_level_zero -lkernel32 -luser32 -lgdi32 -lwinspool -lshell32 -lole32 -loleaut32 -luuid -lcomdlg32 -ladvapi32 && :
ld.lld: error: undefined symbol: __declspec(dllimport) sycl::_V1::ext::oneapi::level_zero::make_platform(unsigned long long)
>>> referenced by /workspace/srcdir/oneAPI.jl/deps/src/sycl.cpp:9
>>> CMakeFiles/oneapi_support.dir/src/sycl.cpp.obj:(syclPlatformCreate)

This despite sycl7.dll and sycl7.lib being available on the library search path, and containing the symbol that's being listed here:

# nm /workspace/destdir/bin/sycl7.lib | grep make_platform
0000000000000000 T ?make_platform@level_zero@oneapi@ext@_V1@sycl@@YA?AVplatform@45@_K@Z
0000000000000000 I __imp_?make_platform@level_zero@oneapi@ext@_V1@sycl@@YA?AVplatform@45@_K@Z

Using ld instead of ldd throws a similar error:

ld: CMakeFiles/oneapi_support.dir/src/sycl.cpp.obj: in function `syclPlatformCreate':
/workspace/srcdir/oneAPI.jl/deps/src/sycl.cpp:9: undefined reference to `__imp__ZN4sycl3_V13ext6oneapi10level_zero13make_platformEy'

What am I doing wrong here? The full build script can be found in https://github.com/JuliaPackaging/Yggdrasil/pull/8285

[tbesard]

It seems like this is a C++ ABI incompatibility between my MinGW-produced objects, and sycl7.dll as compiled with MSVC, as shown above by the different manglings for the make_platform function. I also don't think this is easy to fix, as it's more than the name mangling being incompatible. Although Clang seems to offer some kind of ABI compatibility? https://clang.llvm.org/docs/MSVCCompatibility.html

It's too bad oneMKL and other oneAPI libraries don't offer a simple, portable C API like all other vendor libraries do.