On Fri, 17 Feb 2012 16:08:15 +0400
Konstantin Khlebnikov [off-list ref] wrote:

Config NUMA must be defined for all architectures,
otherwise IS_ENABLED(CONFIG_NUMA) does not work.
Some arch-specific Kconfig already has this stub.
This patch adds it to all remaining.

It would be better to teach IS_ENABLED() to handle this situation.  I
don't think there's a way of doing this with cpp :(

This limitation makes IS_ENABLED pretty dangerous, doesn't it?  It
makes it very easy to introduce build breakage with unexpected Kconfig
combinations.