https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119077
Xi Ruoyao <xry111 at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |xry111 at gcc dot gnu.org --- Comment #1 from Xi Ruoyao <xry111 at gcc dot gnu.org> --- _delay_ms and _delay_us are not provided by GCC. The problem seems whoever authored them wrongly assumes __builtin_avr_delay_cycles would be always available. Not a GCC bug to me.