4.4 Preprocessor Control Options

--define=name[=value]
-Dname[=value]

Define the preprocessor symbol name as having value, or empty. See section Preprocessor.

--include-directory=dir
-I dir

Add dir to include search path.

See section #include.

--no-preprocessor

Disable preprocessor. see section Preprocessor.

--preprocessor=command

Use command instead of the default preprocessor. see section Preprocessor.