how to find out preprocessors defined in linux driver

Question

Is there a way to find out what preprocessors are defined in your linux driver/kernel code when building? I could use a text search tool (I actually did), but I inherit a big tree of linux driver/kernel code. It's so big that my text search tool gets an error when I search for a certain preprocessor in the whole code tree.

Answer 1

gcc can dump all defined macros to stdout in preprocessing mode:

gcc -E -dM foo.c

This includes any macros predefined by the compiler, which can be a little annoying. In any case, you should be able to hack up your Makefile to contain a target that dumps this information to files for each compilation unit.