message: in resolution of [Wsign-compare] warning id 13
  index `i` changed to type `size_t`
diff: @@ -27,7 +27,7 @@ void FftCompute(struct FftState* state, const int16_t* input,
  int16_t* fft_input = state->input;
  // First, scale the input by the given shift.
  - int i;
  + size_t i;
  for (i = 0; i < input_size; ++i) {
  fft_input[i] = static_cast<int16_t>(static_cast<uint16_t>(input[i])
  << input_scale_shift);
  