The /C (for “comment”) option preserves comments during preprocessing with the /E, /P, or /EP options. If you do not specify the /C option, the preprocessor does not pass source-file comments to its output file.
This option is valid only if the /E, /P, or /EP option is also used. These CL options are described later in this chapter.
Example
CL /P /C SAMPLE.C
This example produces a listing named SAMPLE.I. The listing file contains the original source file, including comments, with all preprocessor directives expanded or replaced.