哪个-x用于通过GCC进行预处理？

I need to use GCC (4.8.1 in my case) to run the preprocessor on a file which contains preprocessor directives, but not (necessarily) C/C++ code. These directives can depend on GCC's pre-defined macros, so I have to invoke the preprocessor through GCC instead of directly. I know that I can do that by using GCC's option I need to use GCC (4.8.1 in my case) to run the