Basic CMakefile question for building OpenCV - c++

Question

I am a novice in C++ programming, now having to build the OpenCV from source. I am getting an error related to the cudatoolkit installation
[ 13%] Built target opencv_cudev
[ 13%] Building NVCC (Device) object modules/core/CMakeFiles/cuda_compile.dir/src/cuda/cuda_compile_generated_gpu_mat.cu.o
nvcc fatal : Path to libdevice library not specified
CMake Error at cuda_compile_generated_gpu_mat.cu.o.cmake:266 (message):
Error generating file
/home/bruce/opencv-4.2.0/build/modules/core/CMakeFiles/cuda_compile.dir/src/cuda/./cuda_compile_generated_gpu_mat.cu.o
I look inside the cuda_compile_generated_gpu_mat.cu.o.cmake file and see the following lines.
# Generate the code
cuda_execute_process(
"Generating ${generated_file}"
COMMAND "${CUDA_NVCC_EXECUTABLE}"
"${source_file}"
${format_flag} -o "${generated_file}"
${CCBIN}
${nvcc_flags}
${nvcc_host_compiler_flags}
${CUDA_NVCC_FLAGS}
-DNVCC
${CUDA_NVCC_INCLUDE_ARGS}
)
I want to dig into where it's looking for the libdevice library. I don't know the technique for printing out the meaning of all these parameters. How do I print them out as I execute make?

Answer 1

If you want to debug this, and print the values in each of these CMake variables, you can add the message command to this CMake file:
# Generate the code
cuda_execute_process(
"Generating ${generated_file}"
COMMAND "${CUDA_NVCC_EXECUTABLE}"
"${source_file}"
${format_flag} -o "${generated_file}"
${CCBIN}
${nvcc_flags}
${nvcc_host_compiler_flags}
${CUDA_NVCC_FLAGS}
-DNVCC
${CUDA_NVCC_INCLUDE_ARGS}
)
# Print all the above variables to the console.
message("generated_file: ${generated_file}")
message("CUDA_NVCC_EXECUTABLE: ${CUDA_NVCC_EXECUTABLE}")
message("source_file: ${source_file}")
message("format_flag: ${format_flag}")
message("CCBIN: ${CCBIN}")
message("nvcc_flags: ${nvcc_flags}")
message("nvcc_host_compiler_flags: ${nvcc_host_compiler_flags}")
message("CUDA_NVCC_FLAGS: ${CUDA_NVCC_FLAGS}")
message("CUDA_NVCC_INCLUDE_ARGS: ${CUDA_NVCC_INCLUDE_ARGS}")
If you can modify how cmake is called from the command line, you can add the trace-expand option to print all the CMake calls, and expand the variables used:
cmake --trace-expand ..