cmake add_definitions and COMPILE_DEFINITIONS, how to see them

Question

I want to see what the current set of compiler definitions is in my CMake file. Ones automatically specified and the ones I'd added would be great. The COMPILE_DEFINITIONS macro doesn't appear to contain -- despite what the documentation says.

For example, in the below setup the message never includes GUI_BUILD

add_definitions( -DGUI_BUILD )
message( "COMPILE_DEFINITIONS = ${COMPILE_DEFINITIONS}" )

I don't need to see them in their final form, I just want a quick output to help verify that everything has been configured correctly.

Answer 1

You want to extract the COMPILE_DEFINITIONS property from the directory. E.g. use the following:

add_definitions( -DDebug )
get_directory_property( DirDefs DIRECTORY ${CMAKE_SOURCE_DIR} COMPILE_DEFINITIONS )

Then you can simply iterate over them, e.g.:

foreach( d ${DirDefs} )
    message( STATUS "Found Define: " ${d} )
endforeach()
message( STATUS "DirDefs: " ${DirDefs} )

Note that definitions may also be associated with targets or source-files instead of directories. And note that they can differ between configurations. Depending on your requirements, you may need to check a large set of different properties.