PR #22593 opened by MarcosAsh
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/22593
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/22593.patch
Fixes #22276.
The DEFINE_REMAP macro has a loop condition with a precedence bug:
` for (int stereo = 0; stereo < 1 + s->out_stereo > STEREO_2D; stereo++)`
Because `<` and `>` associate left-to-right at the same precedence level, this
parses as `(stereo < (1 + s->out_stereo)) > STEREO_2D`. Since STEREO_2D is 0,
the outer `> 0` comparison is effectively a no-op for STEREO_2D and STEREO_SBS.
But for STEREO_TB (value 2) the loop runs 3 iterations instead of 2, producing
an out-of-bounds stereo pass.
The fix adds parentheses so the intent is clear:
`for (int stereo = 0; stereo < 1 + (s->out_stereo > STEREO_2D); stereo++)`
This gives 1 iteration for 2D and 2 for any stereo format, matching the number
of actual stereo views.
Recent Clang versions (21.x) flag this without -Wno-parentheses, which is how
the issue was reported.
>From 249409d1fbaa9a9c9e8af682551802c4046d9acd Mon Sep 17 00:00:00 2001
From: marcos ashton <[email protected]>
Date: Mon, 23 Mar 2026 14:08:35 +0000
Subject: [PATCH] libavfilter/vf_v360: fix operator precedence in stereo loop
condition
The loop condition in the DEFINE_REMAP macro:
stereo < 1 + s->out_stereo > STEREO_2D
is parsed by C as:
(stereo < (1 + s->out_stereo)) > STEREO_2D
Since STEREO_2D is 0 and relational operators return 0 or 1, the
outer comparison against 0 is a no-op for STEREO_2D and STEREO_SBS.
But for STEREO_TB (value 2) the loop runs 3 iterations instead of 2,
producing an out-of-bounds stereo pass.
Add parentheses so the comparison is evaluated first:
stereo < 1 + (s->out_stereo > STEREO_2D)
This gives 1 iteration for 2D and 2 for any stereo format (SBS or TB),
matching the actual number of stereo views.
Signed-off-by: marcos ashton <[email protected]>
---
libavfilter/vf_v360.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/libavfilter/vf_v360.c b/libavfilter/vf_v360.c
index a5297c81e9..a08279867f 100644
--- a/libavfilter/vf_v360.c
+++ b/libavfilter/vf_v360.c
@@ -291,7 +291,7 @@ static int remap##ws##_##bits##bit_slice(AVFilterContext
*ctx, void *arg, int jo
\
av_assert1(s->nb_planes <= AV_VIDEO_MAX_PLANES);
\
\
- for (int stereo = 0; stereo < 1 + s->out_stereo > STEREO_2D; stereo++) {
\
+ for (int stereo = 0; stereo < 1 + (s->out_stereo > STEREO_2D); stereo++) {
\
for (int plane = 0; plane < s->nb_planes; plane++) {
\
const unsigned map = s->map[plane];
\
const int in_linesize = in->linesize[plane];
\
--
2.52.0
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