When working with -O2 with avr-gcc 7.2 boundt_avr doesn't find the interp function. I reverted to -O1 which seems to work okay.
(default of -g also has been updated to dwarf-4, which isn't accepted by boundt, I fixed that by specifying -gdwarf-3 for compiling)
- One solution would be to make interp the "main" function of the program, that way it's always found by boundt_avr