Avoiding overflow in cross correlation in NetEq.

webrtc/common_audio/signal_processing/cross_correlation.c

Index: webrtc/common_audio/signal_processing/cross_correlation.c
diff --git a/webrtc/common_audio/signal_processing/cross_correlation.c b/webrtc/common_audio/signal_processing/cross_correlation.c
index d7c9f2b9afede2a0a86d20bf33c082626de2eade..82a42c71b76225ae041c12aa4947190c1a7bdc58 100644
--- a/webrtc/common_audio/signal_processing/cross_correlation.c
+++ b/webrtc/common_audio/signal_processing/cross_correlation.c
@@ -10,6 +10,8 @@
 
 #include "webrtc/common_audio/signal_processing/include/signal_processing_library.h"
 
+#include <assert.h>
+
 /* C version of WebRtcSpl_CrossCorrelation() for generic platforms. */
 void WebRtcSpl_CrossCorrelationC(int32_t* cross_correlation,
                                  const int16_t* seq1,
@@ -22,8 +24,12 @@ void WebRtcSpl_CrossCorrelationC(int32_t* cross_correlation,
 
   for (i = 0; i < dim_cross_correlation; i++) {
     int32_t corr = 0;
-    for (j = 0; j < dim_seq; j++)
-      corr += (seq1[j] * seq2[j]) >> right_shifts;
+    for (j = 0; j < dim_seq; j++) {
+      int32_t old = corr;
+      int32_t add = seq1[j] * seq2[j];
+      corr += add >> right_shifts;
+      assert((add >= 0 && corr >= old) || (add < 0 && corr < old));
+    }
     seq2 += step_seq2;
     *cross_correlation++ = corr;
   }