[Bug target/119077] gcc option -mint8 leads to undefined reference to `__builtin_avr_delay_cycles'

[gjl at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119077

--- Comment #7 from Georg-Johann Lay <gjl at gcc dot gnu.org> ---
...I can reproduce it with the following test case and v13:

#include <stdint.h>

extern void __builtin_avr_delay_cycles (uint32_t);

#include <util/delay.h>

int main(void)
{
    _delay_ms(100);
}

So the likely cause is that AVR-LibC used prototypes for built-ins, which you
should not do.  This was fixed in
https://github.com/avrdudes/avr-libc/commit/5e6f28bd436e6f9749ecc5bc47f9035f1c1e7423