[Bug c/85563] -Wmaybe-uninitialized false alarm regression with __builtin_unreachable and GCC 8

[eggert at cs dot ucla.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85563

--- Comment #1 from eggert at cs dot ucla.edu ---
Created attachment 44035
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=44035&action=edit
sample program illustrating regression

I've gzipped f.i as it is rather large.