5.7.8 Options for Controlling the Preprocessor

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

Table 5-15. Preprocessor Options
Option	Definition
`-C`	Preserve comments.
`-dletters`	Make debugging dumps of preprocessor macros.
`-Dmacro[=defn]`	Define a macro.
`-H`	Print the name of each header file used.
`-imacros file`	Include file macro definitions only.
`-include file`	Process file as input before processing the regular input 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.
`-nostdinc`	Omit system directories from header search.
`-P`	Don’t generate #line directives.
`-f[no-]show-column`	Omit column numbers in diagnostics.
`-trigraphs`	Support ANSI C trigraphs.
`-Umacro`	Undefine a macro.
`-undef`	Do not predefine any nonstandard macros.