Why is this nested macro replacement failing?

Question

I am trying to apply the X Macro concept, in order to have the possibility to initialize all struct members to a custom default (invalid) value. I write the following code:<

Answer 1

You might also try to check the output of expanded macros. If you are using gcc as a compiler, gcc -E >> full_src.txt' shall help. More details are here: Seeing expanded C macros