I have used them countless timers myself, but not within another macro

Edit: Sorry I am on multiple drugs at the moment for a severe fracture - I'm a bit confused, nurse has just been. I will shut up now.

To prove I am not completely out of it (though wrong), here's one I wrote a lot earlier: https://latedev.wordpress.com/2012/08/09/c-debug-macros/

Sorry to hear that! Rest up and don’t worry about cpp macros for now ;) they’ll still be there after you heal. Good luck!

Honestly, I suspect that cpp macros will outlive us all

most commonly they are typically used in the definition of the assert macro. For example: https://github.com/lattera/glibc/blob/master/assert/assert.h .