Out of Memory Handler

[wesner0019]

For this handler, how is the out of memory calculated? I tried searching within github, but I couldn’t find it.

System.on(out_of_memory, outOfMemoryHandler);

[wesner0019]

Is it calculated to something like this?

void fragmentationCheck() {
  static uint32_t prevFragCheckMillis = 0;
  static uint32_t prevFragPublishMillis = 0;
  static uint32_t freeMemory = 0;
  static uint32_t largestBlock = 0;
  static float fragmentationPercent = 0;
  static bool runAtStartup = true;

  if ((millis() - prevFragCheckMillis > (60000 * 60)) || runAtStartup) {
    runtime_info_t info;
    memset(&info, 0, sizeof(info));
    info.size = sizeof(info);
    HAL_Core_Runtime_Info(&info, NULL);
    largestBlock = info.largest_free_block_heap;
    freeMemory = System.freeMemory();

    fragmentationPercent = ((1 - ((static_cast<float>(largestBlock)) / freeMemory)) * 100.0);
    // Serial.print("largestBlock : ");Serial.print(largestBlock);
    // Serial.print("   freeMemory : ");Serial.print(freeMemory);
    // Serial.print("   fragmentationPercent : ");Serial.println(fragmentationPercent);

    char memoryCharArray[80];
      snprintf(memoryCharArray, sizeof(memoryCharArray),
        "%u.%u.%.2f.%u"
        , largestBlock
        , freeMemory
        , fragmentationPercent
        , Time.now()
      );
    
    if (millis() - prevFragPublishMillis > (24*60*60*1000)) { // publish every 24 hours
      #if PLATFORM_ID == PLATFORM_ELECTRON_PRODUCTION
        publishAsync("fragInfo", memoryCharArray);
      #elif PLATFORM_ID == PLATFORM_P1
        if (Particle.connected() && WiFi.ready()) {
          Particle.publish("fragInfo", memoryCharArray, 60, PRIVATE);
        }
      #endif
      prevFragPublishMillis = millis();
    }
    
    if (fragmentationPercent > 50.0) { //reset device if too fragmented
      #if PLATFORM_ID == PLATFORM_ELECTRON_PRODUCTION
        publishAsync("fragRst", memoryCharArray);
      #elif PLATFORM_ID == PLATFORM_P1
        if (Particle.connected() && WiFi.ready()) {
          Particle.publish("fragRst", memoryCharArray, 60, PRIVATE);
        }
      #endif
      delay(2000);
      System.reset();
    }

    runAtStartup = false;
    prevFragCheckMillis = millis();
  } 
}

[rickkas7]

The out of memory handler happens when a memory allocation (malloc, new, strdup, etc.) fails. This occurs whenever the largest free block if smaller than the allocation request size, regardless of how much is available in total.