integer overflow in expression of type 'int' results

Question

i need to wake up my ESP every 60 min to read some data and post it to server, all process working fine when i use numbers of minute below 60 (converted in microsecond x 1000000) but when i use 60 min above i get the following message:

src/main.cpp:137:49: warning: integer overflow in expression of type 'int' results in '-694967296' [-Woverflow] esp_sleep_enable_timer_wakeup(TIME_TO_SLEEP * uS_TO_S_FACTOR);// set up next wake up after 30 sec

How can i make my ESP wake up every 60 min or above?

simplify code:

// for awake and sleep
#define uS_TO_S_FACTOR 1000000 
#define TIME_TO_SLEEP 60 // minute
void setup(){
esp_sleep_enable_timer_wakeup(TIME_TO_SLEEP * 60 * uS_TO_S_FACTOR);// error if time to sleep more than 60 min 
}

• timemage: More or less the same question here. On the ESP32 the long and int types have the same range.

Answer 1

Change that line to:

esp_sleep_enable_timer_wakeup((uint64_t) TIME_TO_SLEEP * 60 * uS_TO_S_FACTOR);

That forces the compiler to do 64-bit arithmetic on the constant rather than defaulting to "int" arithmetic.