[berti]

Just to add more context, this is a very common cpp (c pre-processor) idiom. You'll find it in most non-trivial C projects somewhere.

[pantalaimon]

Abbreviating the C Preprocessor as cpp is very confusing imho.

[monocasa]

It's a common abbreviation older than C++. You used to even be able to run the c pre processor on arbitrary non-C files by using the cpp command.

[berti]

You still can.

[saagarjha]

Tell that to CPPFLAGS.