Defines symbol name to the preprocessor.

-Dname[=def]

"-Dname[=def]"

Runs preprocessor on C++ source files and sends result to stdout. Does not compile.

-E

"-E"

Only preprocesses source; outputs to .i file.

-P

"-P"

Deletes initial definition of preprocessor symbol name.

-Uname

"-Uname"

Outputs makefile dependency information. 

-xM

"-xM"

Generates dependency information, but excludes 

/usr/include.

-xM1

"-xM1"