Fix ptr overflow warning in filter_ar.c
In this code, the problem was that the ptr could sometimes point
outside of the allocated arrays, in particular before the array,
causing a pointer overflow warning. However, the memory pointed to was
never read or written while the pointer was off.
With this change, we keep an index instead of a pointer, which avoids
warnings for pointer overflow. The index might be negative at times,
but the index will not be used to address the arrays while negative.
Bug: webrtc:9166
Change-Id: I3a32d8e814660f43be9d4c94889d00ac3f8403a5
Reviewed-on: https://webrtc-review.googlesource.com/71165
Reviewed-by: Artem Titov <titovartem@webrtc.org>
Commit-Queue: Henrik Lundin <henrik.lundin@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22951}diff --git a/common_audio/signal_processing/filter_ar.c b/common_audio/signal_processing/filter_ar.c
index 49d5d61..2471cd1 100644
--- a/common_audio/signal_processing/filter_ar.c
+++ b/common_audio/signal_processing/filter_ar.c
@@ -17,6 +17,8 @@
#include "common_audio/signal_processing/include/signal_processing_library.h"
+#include "rtc_base/checks.h"
+
size_t WebRtcSpl_FilterAR(const int16_t* a,
size_t a_length,
const int16_t* x,
@@ -40,8 +42,10 @@
{
// Calculate filtered[i] and filtered_low[i]
const int16_t* a_ptr = &a[1];
- int16_t* filtered_ptr = &filtered[i - 1];
- int16_t* filtered_low_ptr = &filtered_low[i - 1];
+ // The index can become negative, but the arrays will never be indexed
+ // with it when negative. Nevertheless, the index cannot be a size_t
+ // because of this.
+ int filtered_ix = (int)i - 1;
int16_t* state_ptr = &state[state_length - 1];
int16_t* state_low_ptr = &state_low[state_length - 1];
@@ -51,8 +55,10 @@
stop = (i < a_length) ? i + 1 : a_length;
for (j = 1; j < stop; j++)
{
- o -= *a_ptr * *filtered_ptr--;
- oLOW -= *a_ptr++ * *filtered_low_ptr--;
+ RTC_DCHECK_GE(filtered_ix, 0);
+ o -= *a_ptr * filtered[filtered_ix];
+ oLOW -= *a_ptr++ * filtered_low[filtered_ix];
+ --filtered_ix;
}
for (j = i + 1; j < a_length; j++)
{
