https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117681
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
@deftypefn {Target Hook} scalar_int_mode TARGET_UNWIND_WORD_MODE (void)
Return machine mode to be used for @code{_Unwind_Word} type.
The default is to use @code{word_mode}.
@end deftypefn
and avr.h has
#ifdef IN_LIBGCC2
/* This is to get correct SI and DI modes in libgcc2.c (32 and 64 bits). */
#define UNITS_PER_WORD 4
#else
/* Width of a word, in units (bytes). */
#define UNITS_PER_WORD 1
#endif
#define POINTER_SIZE 16
I'm not sure how this all plays out, but it looks like _Unwind_Word doesn't
match pointer size and it looks like a AVR target setup issue. Note this
might be part of the ABI now.
