-cpp_opt 'command

-cpp_opt 'command_options'

Specifies additional options to be passed to the C preprocessor. You can add options to the command line used to invoke the C preprocessor independent of the -cpp_cmd argument. The IDL compiler concatenates the -cpp_cmd, -cpp_opt, -D, -U, -I arguments and the source file name into a command used to invoke the C preprocessor. The compiler repeats this process for each attribute configuration file (ACF) and IDL file.