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[FFmpeg-devel,PATCHv2] swscale: prevent undefined behaviour in the PUTRGBA macro

Message ID 20240708042517.5585-1-gseanmcg@gmail.com
State New
Headers show
Series [FFmpeg-devel,PATCHv2] swscale: prevent undefined behaviour in the PUTRGBA macro | expand

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Commit Message

Sean McGovern July 8, 2024, 4:25 a.m. UTC 
---
 libswscale/yuv2rgb.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

Michael Niedermayer July 9, 2024, 12:44 p.m. UTC | #1 
On Mon, Jul 08, 2024 at 12:25:17AM -0400, Sean McGovern wrote:
> ---
>  libswscale/yuv2rgb.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/libswscale/yuv2rgb.c b/libswscale/yuv2rgb.c
> index 977eb3a7dd..ac0b811f61 100644
> --- a/libswscale/yuv2rgb.c
> +++ b/libswscale/yuv2rgb.c
> @@ -100,9 +100,9 @@ const int *sws_getCoefficients(int colorspace)
>  
>  #define PUTRGBA(dst, ysrc, asrc, i, abase)                              \
>      Y              = ysrc[2 * i];                                       \
> -    dst[2 * i]     = r[Y] + g[Y] + b[Y] + (asrc[2 * i]     << abase);   \
> +    dst[2 * i]     = r[Y] + g[Y] + b[Y] + ((int32_t)(asrc[2 * i])     << abase);   \
>      Y              = ysrc[2 * i + 1];                                   \
> -    dst[2 * i + 1] = r[Y] + g[Y] + b[Y] + (asrc[2 * i + 1] << abase);
> +    dst[2 * i + 1] = r[Y] + g[Y] + b[Y] + ((int32_t)(asrc[2 * i + 1]) << abase);

can you explain what undefined behavior this does prevent and how ?
(in the commit message)

thx

[...]
diff mbox series

Patch

diff --git a/libswscale/yuv2rgb.c b/libswscale/yuv2rgb.c
index 977eb3a7dd..ac0b811f61 100644
--- a/libswscale/yuv2rgb.c
+++ b/libswscale/yuv2rgb.c
@@ -100,9 +100,9 @@  const int *sws_getCoefficients(int colorspace)
 
 #define PUTRGBA(dst, ysrc, asrc, i, abase)                              \
     Y              = ysrc[2 * i];                                       \
-    dst[2 * i]     = r[Y] + g[Y] + b[Y] + (asrc[2 * i]     << abase);   \
+    dst[2 * i]     = r[Y] + g[Y] + b[Y] + ((int32_t)(asrc[2 * i])     << abase);   \
     Y              = ysrc[2 * i + 1];                                   \
-    dst[2 * i + 1] = r[Y] + g[Y] + b[Y] + (asrc[2 * i + 1] << abase);
+    dst[2 * i + 1] = r[Y] + g[Y] + b[Y] + ((int32_t)(asrc[2 * i + 1]) << abase);
 
 #define PUTRGB48(dst, src, asrc, i, abase)          \
     Y                = src[ 2 * i];                 \