mark alarm.wake_alarm during gc sweep

Author: dhalbert

main.c

@@ -613,6 +613,10 @@ void gc_collect(void) {
 
     background_callback_gc_collect();
 
+    #if CIRCUITPY_ALARM
+    common_hal_alarm_gc_collect();
+    #endif
+
     #if CIRCUITPY_DISPLAYIO
     displayio_gc_collect();
     #endif

ports/esp32s2/common-hal/alarm/__init__.c

@@ -25,10 +25,12 @@
  * THE SOFTWARE.
  */
 
+#include "py/gc.h"
 #include "py/obj.h"
 #include "py/objtuple.h"
 #include "py/runtime.h"
 
+#include "shared-bindings/alarm/__init__.h"
 #include "shared-bindings/alarm/pin/PinAlarm.h"
 #include "shared-bindings/alarm/SleepMemory.h"
 #include "shared-bindings/alarm/time/TimeAlarm.h"
@@ -38,8 +40,6 @@
 #include "supervisor/port.h"
 #include "supervisor/shared/workflow.h"
 
-#include "common-hal/alarm/__init__.h"
-
 #include "esp_sleep.h"
 
 #include "components/soc/soc/esp32s2/include/soc/rtc_cntl_reg.h"
@@ -159,3 +159,7 @@ void NORETURN alarm_enter_deep_sleep(void) {
     // We don't need to worry about resetting them in the interim.
     esp_deep_sleep_start();
 }
+
+void common_hal_alarm_gc_collect(void) {
+    gc_collect_ptr(alarm_get_wake_alarm());
+}

shared-bindings/alarm/__init__.c

@@ -199,7 +199,18 @@ STATIC mp_map_elem_t alarm_module_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR_SleepMemory),   MP_OBJ_FROM_PTR(&alarm_sleep_memory_type) },
     { MP_ROM_QSTR(MP_QSTR_sleep_memory),  MP_OBJ_FROM_PTR(&alarm_sleep_memory_obj) },
 };
-STATIC MP_DEFINE_MUTABLE_DICT(alarm_module_globals, alarm_module_globals_table);
+MP_DEFINE_MUTABLE_DICT(alarm_module_globals, alarm_module_globals_table);
+
+// Fetch value from module dict.
+mp_obj_t alarm_get_wake_alarm(void) {
+    mp_map_elem_t *elem =
+        mp_map_lookup(&alarm_module_globals.map, MP_ROM_QSTR(MP_QSTR_wake_alarm), MP_MAP_LOOKUP);
+    if (elem) {
+        return elem->value;
+    } else {
+        return NULL;
+    }
+}
 
 STATIC void alarm_set_wake_alarm(mp_obj_t alarm) {
     // Equivalent of:

shared-bindings/alarm/__init__.h

@@ -31,6 +31,9 @@
 
 #include "common-hal/alarm/__init__.h"
 
+// Make module dict available elsewhere, so we can fetch
+extern mp_obj_dict_t alarm_module_globals;
+
 extern mp_obj_t common_hal_alarm_light_sleep_until_alarms(size_t n_alarms, const mp_obj_t *alarms);
 
 // Deep sleep is a two step process. Alarms are set when the VM is valid but
@@ -43,6 +46,10 @@ extern void common_hal_alarm_set_deep_sleep_alarms(size_t n_alarms, const mp_obj
 // Deep sleep is entered outside of the VM so we omit the `common_hal_` prefix.
 extern NORETURN void alarm_enter_deep_sleep(void);
 
+// Fetches value from module dict.
+extern mp_obj_t alarm_get_wake_alarm(void);
+
+extern void common_hal_alarm_gc_collect(void);
 extern mp_obj_t common_hal_alarm_get_wake_alarm(void);
 
 // Used by wake-up code.
@@ -52,4 +59,5 @@ void alarm_save_wakeup_alarm(void);
 // True if an alarm is alerting. This is most useful for pretend deep sleep.
 extern bool alarm_woken_from_sleep(void);
 
+
 #endif  // MICROPY_INCLUDED_SHARED_BINDINGS_ALARM___INIT___H