probably aren't useful, but if you really want to push GNU Make syntax to its limits try this:
Yes, that defines a variable called + containing a +.
When I first blogged about some of this, I received the following warning from Paul Smith (the maintainer of GNU Make):
I don't recommend using a space as a variable name. I've toyed with the idea of allowing some special syntactic sugar for user-defined functions, that would allow you to omit the $(call ...) prefix and just invoke the user-defined function directly, like:
$(my-func arg1, arg2)
Obviously the way this works is that if make detects a space in the variable name, it would assume that it is a user-defined function. If this were to happen I'd probaby make whitespace in variable names illegal, just to cut down on confusion and bizarre misbehaviors.
OK, I'll be careful.