[FFmpeg-cvslog] avcodec/snow: Don't add to NULL

[Andreas Rheinhardt]

ffmpeg | branch: master | Andreas Rheinhardt <andreas.rheinhardt at outlook.com> | Mon Mar 17 09:59:36 2025 +0100| [02c16b48c5827b9383004ad5a727742b30614fe7] | committer: Andreas Rheinhardt

avcodec/snow: Don't add to NULL

It is undefined behavior.
Fixes "runtime error: applying non-zero offset 8 to null pointer".
Fixes the Snow vsynth FATE-tests.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at outlook.com>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=02c16b48c5827b9383004ad5a727742b30614fe7
---

 libavcodec/snow.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/libavcodec/snow.h b/libavcodec/snow.h
index ff7ebc1c58..9b19e70bd5 100644
--- a/libavcodec/snow.h
+++ b/libavcodec/snow.h
@@ -272,7 +272,8 @@ static av_always_inline void add_yblock(SnowContext *s, int sliced, slice_buffer
 
     if(!sliced && offset_dst)
         dst += src_x + src_y*dst_stride;
-    dst8+= src_x + src_y*src_stride;
+    if (sliced || add)
+        dst8+= src_x + src_y*src_stride;
 //    src += src_x + src_y*src_stride;
 
     ptmp= tmp + 3*tmp_step;