This warning can happen on clang 13.0.1 building mpy-cross:
../py/vm.c:748:25: error: array index -3 refers past the last possible
element for an array in 64-bit address space containing 64-bit (8-byte)
elements (max possible 2305843009213693952 elements)
[-Werror,-Warray-bounds]
sp[-MP_OBJ_ITER_BUF_NSLOTS + 1] = MP_OBJ_NULL;
^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~
Using pointer access instead of array access works around this warning.
Fixes issue #8467.
Signed-off-by: Damien George <damien@micropython.org>
Some audio implementations, notably samd, really don't like it when
you return 0 samples of data. This was the case when reaching the
end of an MP3 file.
Now, we read forward in an MP3 file to the next sync word during
"get_buffer", so that we can accurately return GET_BUFFER_DONE when the
NEXT call WOULD HAVE resulted in 0 samples.
Tested with @gamblor21's "laugh.mp3" file on a Trellis M4 Express.
I instrumented RTC_Handler and determined that on SAMD51 it was possible
for the interrupt to be delivered well before the actual overflow of the
RTC COUNT register (e.g., a value as small as 0xffff_fffd could be seen
at the time of overflow)
Rather than depending on the overflow interrupt coming in at the same time
as COUNT overflows (exactly), rely only on observed values of COUNT in
_get_count, overflowing when it wraps around from a high value to a low
one.
With this change, PLUS a second change so that it is possible to warp
the RTC counter close to an overflow and test in 20ms instead of 3 days,
there was no problem detected over 20000+ overflows. Before, a substantial
fraction (much greater than 10%) of overflows failed.
Fixes#5985
Change to common-hal/rtc/RTC.c for time warping (plus make rtc_old_count non-static):
```patch
void common_hal_rtc_set_calibration(int calibration) {
+
+ common_hal_mcu_disable_interrupts();
+
+ RTC->MODE0.COUNT.reg = 0xffffff00;
+ rtc_old_count = 0;
+ do {
+ while ((RTC->MODE0.SYNCBUSY.reg & (RTC_MODE0_SYNCBUSY_COUNTSYNC | RTC_MODE0_SYNCBUSY_COUNT)) != 0) { }
+ }
+ while(RTC->MODE0.COUNT.reg < 0xffffff00);
+ common_hal_mcu_enable_interrupts();
+
+ mp_printf(&mp_plat_print, "Warping RTC in calibration setter count=%08x rtc_old_count=%08x\n", RTC->MODE0.COUNT.reg, rtc_old_count);
```
Test program:
```python
import time
from rtc import RTC
i = 0
while True:
RTC().calibration = 1 # Warps to ~16ms before overflow, with patch to RTC code
t0 = time.monotonic_ns()
et = t0 + 20_000_000 # 20ms
while (t1 := time.monotonic_ns()) < et: pass
i += 1
print(f"{i:6d}: duration {t1-t0}")
if t1-t0 > 200_000_000: break
print()
```
