3.6.7 Options for Controlling the Preprocessor

The options tabulated below control the preprocessor and are discussed in the sections that follow.

Table 3-17. Preprocessor Options
Option (links to explanatory section)	Controls
`-C`	Preserve comments
`-dletters`	Preserve macro definitions
`-Dmacro` `-Dmacro=defn`	Define a macro
`-fno-show-column`	Omit column numbers in diagnostics
`-H`	Print header file name
`-imacros file`	Include file macro definitions only
`-include file`	Include file
`-M`	Generate make rule
`-MD`	Write dependency information to file
`-MF file`	Specify dependency file
`-MG`	Ignore missing header files
`-MM`	Generate make rule for quoted headers
`-MMD`	Generate make rule for user headers
`-MP`	Add phony target for dependency
`-MQ`	Change rule target with quotes
`-MT target`	Change rule target
`-P`	Don’t generate #line directives
`-trigraphs`	Support trigraphs
`-Umacro`	Undefine macros
`-undef`	Do not predefine nonstandard macros