[FFmpeg-devel] [PATCH] dv: fix valgrind use of uninitialised value warnings.

[Clément Bœsch]

From: Clément Bœsch <clement.boesch at smartjog.com>

---
Hi,

As the subject says, the patch fixes valgrind warnings I expect with a DV100
file. I'm not sure this is a false positive from valgrind thought, and
unfortunately the sample I use can't be shared.

Here is an extract of expected warnings:

    ==8399== Use of uninitialised value of size 4
    ==8399==    at 0x82800A4: dv_decode_ac (dv.c:413)
    ==8399==    by 0x82840EB: dv_decode_video_segment (dv.c:550)
    ==8399==    by 0x8482A85: avcodec_default_execute (utils.c:440)
    ==8399==    by 0x8280BB2: dvvideo_decode_frame (dv.c:1098)
    ==8399==    by 0x8483611: avcodec_decode_video2 (utils.c:747)
    ==8399==    by 0x804CB59: output_packet (ffmpeg.c:1611)
    ==8399==    by 0x808D2A1: transcode.constprop.24 (ffmpeg.c:2781)
    ==8399==    by 0x8087A75: main (ffmpeg.c:4583)
    ==8399== 
    ==8399== Use of uninitialised value of size 4
    ==8399==    at 0x828011F: dv_decode_ac (dv.c:410)
    ==8399==    by 0x82840EB: dv_decode_video_segment (dv.c:550)
    ==8399==    by 0x8482A85: avcodec_default_execute (utils.c:440)
    ==8399==    by 0x8280BB2: dvvideo_decode_frame (dv.c:1098)
    ==8399==    by 0x8483611: avcodec_decode_video2 (utils.c:747)
    ==8399==    by 0x804CB59: output_packet (ffmpeg.c:1611)
    ==8399==    by 0x808D2A1: transcode.constprop.24 (ffmpeg.c:2781)
    ==8399==    by 0x8087A75: main (ffmpeg.c:4583)
    ==8399== 
    ==8399== Use of uninitialised value of size 4e=00:00:01.06 bitrate=2804.1kbits/s    
    ==8399==    at 0x8280111: dv_decode_ac (dv.c:408)
    ==8399==    by 0x8284356: dv_decode_video_segment (dv.c:572)
    ==8399==    by 0x8482A85: avcodec_default_execute (utils.c:440)
    ==8399==    by 0x8280BB2: dvvideo_decode_frame (dv.c:1098)
    ==8399==    by 0x8483611: avcodec_decode_video2 (utils.c:747)
    ==8399==    by 0x804CB59: output_packet (ffmpeg.c:1611)
    ==8399==    by 0x808D2A1: transcode.constprop.24 (ffmpeg.c:2781)
    ==8399==    by 0x8087A75: main (ffmpeg.c:4583)
    ==8399== 

Note: it is not a regression (the issue is present since the first DV100
support was added).

---
 libavcodec/dv.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/libavcodec/dv.c b/libavcodec/dv.c
index d6c49c8..f426d73 100644
--- a/libavcodec/dv.c
+++ b/libavcodec/dv.c
@@ -476,8 +476,8 @@ static int dv_decode_video_segment(AVCodecContext *avctx, void *arg)
     GetBitContext gb;
     BlockInfo mb_data[5 * DV_MAX_BPM], *mb, *mb1;
     LOCAL_ALIGNED_16(DCTELEM, sblock, [5*DV_MAX_BPM], [64]);
-    LOCAL_ALIGNED_16(uint8_t, mb_bit_buffer, [80 + 4]); /* allow some slack */
-    LOCAL_ALIGNED_16(uint8_t, vs_bit_buffer, [5 * 80 + 4]); /* allow some slack */
+    LOCAL_ALIGNED_16(uint8_t, mb_bit_buffer, [80 + 4])     = {0}; /* allow some slack */
+    LOCAL_ALIGNED_16(uint8_t, vs_bit_buffer, [5 * 80 + 4]) = {0}; /* allow some slack */
     const int log2_blocksize = 3-s->avctx->lowres;
     int is_field_mode[5];
 
-- 
1.7.5.4