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Fix 'Left shift cannot be represented in int32_t'.

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In the legacy C part of AGC, an audio level 'cur_level' is represented as

  (1+frac) * 2^(31 - zeros)

The 'zeros' exponent part is used for looking up a gain value in a
table, and 'frac' is used for interpolating between two nearby table
values. Code snippet below:

  zeros = WebRtcSpl_NormU32((uint32_t)cur_level);
  tmp32 = (cur_level << zeros) & 0x7FFFFFFF;
  frac = (int16_t)(tmp32 >> 19);

In the second line, 'cur_level' is shifted upwards so that the leading
bit is '1', after which the leading bit is cleared. The result is
'frac' in Q31.

The compiler type of 'cur_level << zeros' is 'int32_t'. This is a
fuzzer error 'Left shift cannot be represented in int32_t', 
because the leading sign bit is 1. This CL changes the compiler type to
uint32_t.

Bug: chromium:776286
Change-Id: Ie29552b75e690057bd76fc88e747841b531e3802
Reviewed-on: https://webrtc-review.googlesource.com/14841
Reviewed-by: Alessio Bazzica <alessiob@webrtc.org>
Commit-Queue: Alex Loiko <aleloi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20405}
This commit is contained in:
Alex Loiko
2017-10-24 10:41:48 +02:00
committed by Commit Bot
parent 330bf4076e
commit c531af77c3
1 changed files with 2 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
modules/audio_processing/agc/legacy/digital_agc.c
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@ -410,7 +410,7 @@ int32_t WebRtcAgc_ProcessDigital(DigitalAgc* stt,
if (cur_level == 0) {
zeros = 31;
}
tmp32 = (cur_level << zeros) & 0x7FFFFFFF;
tmp32 = ((uint32_t)cur_level << zeros) & 0x7FFFFFFF;
frac = (int16_t)(tmp32 >> 19); // Q12.
tmp32 = (stt->gainTable[zeros - 1] - stt->gainTable[zeros]) * frac;
gains[k + 1] = stt->gainTable[zeros] + (tmp32 >> 12);
@ -429,7 +429,7 @@ int32_t WebRtcAgc_ProcessDigital(DigitalAgc* stt,
if (stt->capacitorFast == 0) {
zeros_fast = 31;
}
tmp32 = (stt->capacitorFast << zeros_fast) & 0x7FFFFFFF;
tmp32 = ((uint32_t)stt->capacitorFast << zeros_fast) & 0x7FFFFFFF;
zeros_fast <<= 9;
zeros_fast -= (int16_t)(tmp32 >> 22);