mbl_mw_datasignal_log Crashes

rlin · December 2018

Hi I'm investigating a case where mbl_mw_datasignal_log is called after sensor is disconnected unexpectedly and leads to app crashing. The line crashes happen is state->create_next(true); inside the mbl_mw_datasignal_log timeout. The exception can't be handled in our code because it is outside the logger callback. Is this a bug in the SDK or are we missing something? The code works fine if it is connected. This only happens if the sensor is disconnected.

The following code should show the crash described:

device.apiAccessQueue.async {
    if let signal = mbl_mw_sensor_fusion_get_data_signal(device.board,
                    MBL_MW_SENSOR_FUSION_DATA_CORRECTED_ACC) {
        mbl_mw_metawearboard_set_time_for_response(device.board, 2000)
        // Simulates unexpected disconnection
        mbl_mw_debug_disconnect(device.board)
        mbl_mw_datasignal_log(signal, nil, { (context, logger) in
            if let logger = logger {
                // Set Logger
            } else {
                // Handles nil
            }
        })
    }
}

rlin · December 2018

Changing if (force) to if (force && !pending_fns.empty()) in C++ SDK's AsyncCreator::create_next seems to fix the problem. Does this make sense?

void AsyncCreator::create_next(bool force) {
    // if (force) {
    if (force && !pending_fns.empty()) {
        pending_fns.pop();
    }
    if ((force && !pending_fns.empty()) || (!force && pending_fns.size() == 1)) {
        pending_fns.front()();
    }
}

Eric · December 2018

Yes, the empty check should happen since the disconnect handler clears the pending_fns queue.

Thanks for bringing that up. We'll add that in the next release

rlin · January 2019

Hi Eric, is there any updates with the fix?
Thanks.

Eric · January 2019

Sorry, it slipped through the cracks. An update to the C++ sdk has been pushed with this change.

rlin · February 2019

@Eric said:
Sorry, it slipped through the cracks. An update to the C++ sdk has been pushed with this change.

I saw the fix in C++ SDK, but it's not part of the latest ios 3.2.0 pod. Can it be included in the next ios sdk update?
Thanks!

Eric · February 2019

@rlin said:

@Eric said:
Sorry, it slipped through the cracks. An update to the C++ sdk has been pushed with this change.

I saw the fix in C++ SDK, but it's not part of the latest ios 3.2.0 pod. Can it be included in the next ios sdk update?
Thanks!

Yes

mbl_mw_datasignal_log Crashes

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