A compile error about sitl

ArduCopter
2

You’re not doing anything wrong.

That’s a bug in the code.

@andyp1per

A patch like this might get you going:

diff --git a/libraries/AP_GyroFFT/AP_GyroFFT.cpp b/libraries/AP_GyroFFT/AP_GyroFFT.cpp
index 849be3ebe6..ebf9277f0a 100644
--- a/libraries/AP_GyroFFT/AP_GyroFFT.cpp
+++ b/libraries/AP_GyroFFT/AP_GyroFFT.cpp
@@ -384,7 +384,7 @@ uint16_t AP_GyroFFT::run_cycle()
     FloatBuffer& gyro_buffer = (_sample_mode == 0 ?_ins->get_raw_gyro_window(_update_axis) : _downsampled_gyro_data[_update_axis]);
     // if we have many more samples than the window size then we are struggling to 
     // stay ahead of the gyro loop so drop samples so that this cycle will use all available samples
-    if (gyro_buffer.available() > _state->_window_size + uint16_t(_samples_per_frame >> 1)) { // half the frame size is a heuristic
+    if (gyro_buffer.available() > unsigned(_state->_window_size + uint16_t(_samples_per_frame >> 1))) { // half the frame size is a heuristic
         gyro_buffer.advance(gyro_buffer.available() - _state->_window_size);
     }
     // let's go!

(that’s probably not the correct fix, but you probably don’t care about that!)