Avoid overflow in WebRtcSpl_DotProductWithScale

webrtc/common_audio/signal_processing/dot_product_with_scale.c

 /*
  *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #include "webrtc/common_audio/signal_processing/include/signal_processing_library.h"
 
 int32_t WebRtcSpl_DotProductWithScale(const int16_t* vector1,
                                       const int16_t* vector2,
                                       size_t length,
                                       int scaling) {
-  int32_t sum = 0;
+  int64_t sum = 0;
   size_t i = 0;
 
   /* Unroll the loop to improve performance. */
   for (i = 0; i + 3 < length; i += 4) {
     sum += (vector1[i + 0] * vector2[i + 0]) >> scaling;
     sum += (vector1[i + 1] * vector2[i + 1]) >> scaling;
     sum += (vector1[i + 2] * vector2[i + 2]) >> scaling;
     sum += (vector1[i + 3] * vector2[i + 3]) >> scaling;
   }
   for (; i < length; i++) {
     sum += (vector1[i] * vector2[i]) >> scaling;
   }
 
-  return sum;
+  return (int32_t) sum;

[kwiberg-webrtc, 2017/02/28 10:07:47]

You'll get garbage if this cast truncates. And wasn't the reason for this change
that the int32_t sum was found to be overflowing?

Suggestion: This is a tiny file. Convert it to C++ so that you can use
saturated_cast.

[hlundin-webrtc, 2017/02/28 11:58:45]

Done.

 }