Merge pull request opencv#17805 from tomoaki0705:fixCUDAHostCompilerIssue

Author: alalek

cmake/OpenCVDetectCUDA.cmake

@@ -106,7 +106,18 @@ if(CUDA_FOUND)
   if(OPENCV_CUDA_DETECTION_NVCC_FLAGS MATCHES "-ccbin")
     # already specified by user
   elseif(CUDA_HOST_COMPILER AND EXISTS "${CUDA_HOST_COMPILER}")
-    LIST(APPEND OPENCV_CUDA_DETECTION_NVCC_FLAGS -ccbin "${CUDA_HOST_COMPILER}")
+    get_filename_component(c_compiler_realpath "${CMAKE_C_COMPILER}" REALPATH)
+    # C compiler doesn't work with --run option, forcing C++ compiler instead
+    if(CUDA_HOST_COMPILER STREQUAL c_compiler_realpath OR CUDA_HOST_COMPILER STREQUAL CMAKE_C_COMPILER)
+      if(DEFINED CMAKE_CXX_COMPILER)
+        get_filename_component(cxx_compiler_realpath "${CMAKE_CXX_COMPILER}" REALPATH)
+        LIST(APPEND OPENCV_CUDA_DETECTION_NVCC_FLAGS -ccbin "${cxx_compiler_realpath}")
+      else()
+        message(STATUS "CUDA: CMAKE_CXX_COMPILER is not available. You may need to specify CUDA_HOST_COMPILER.")
+      endif()
+    else()
+      LIST(APPEND OPENCV_CUDA_DETECTION_NVCC_FLAGS -ccbin "${CUDA_HOST_COMPILER}")
+    endif()
   elseif(WIN32 AND CMAKE_LINKER) # Workaround for VS cl.exe not being in the env. path
     get_filename_component(host_compiler_bindir ${CMAKE_LINKER} DIRECTORY)
     LIST(APPEND OPENCV_CUDA_DETECTION_NVCC_FLAGS -ccbin "${host_compiler_bindir}")