message: [compiler flag] Issue a warning if class has virtual method but missing virtual dtor.
diff: @@ -37,6 +37,7 @@ file(READ "${PROJECT_SOURCE_DIR}/VERSION_NUMBER" ONNX_VERSION)
  string(STRIP "${ONNX_VERSION}" ONNX_VERSION)
  if(NOT MSVC)
  + set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wnon-virtual-dtor")
  set(CMAKE_C_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -O0")
  set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -O0")
  if(ONNX_COVERAGE)
  