[Bug preprocessor/89738] Warn for unused macro arguments

[david.bolvansky at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89738

--- Comment #2 from Dávid Bolvanský <david.bolvansky at gmail dot com> ---
#define PARENT_NODE(x) ((id - 1) / 2)

int id = 0;
int idx = 1;
PARENT_NODE(idx); // macro contais id, but id is defined, warn?


But probably such analysis is not so easy...