This option instructs the compiler to execute only the preprocessor step.
By default, output from the preprocessor is sent to the standard output stream and can be redirected to a file using standard UNIX and MS-DOS notation.
You can also use the
-o option to specify
a file for the preprocessed output. By default, comments are stripped
from the output. The preprocessor accepts source files with any extension,
To generate interleaved macro definitions and preprocessor