[FFmpeg-devel] [PATCH] avcodec/indeo3data: fix undefined left shift of negative number

[Ganesh Ajjanagadde]

This fixes a whole sea of -Wshift-negative-value reported with clang 3.7+, e.g
http://fate.ffmpeg.org/log.cgi?time=20150918181527&log=compile&slot=x86_64-darwin-clang-polly-vectorize-stripmine-3.7.
Any half decent compiler should anyway optimize away the multiplication.

Signed-off-by: Ganesh Ajjanagadde <gajjanagadde at gmail.com>
---
 libavcodec/indeo3data.h | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/libavcodec/indeo3data.h b/libavcodec/indeo3data.h
index e7e28a3..7a2df12 100644
--- a/libavcodec/indeo3data.h
+++ b/libavcodec/indeo3data.h
@@ -237,10 +237,11 @@
  * Pack two delta values (a,b) into one 16bit word
  * according with endianness of the host machine.
  */
+#define POW_2(n) (1 << (n))
 #if HAVE_BIGENDIAN
-#define PD(a,b) (((a) << 8) + (b))
+#define PD(a,b) (((a) * POW_2(8)) + (b))
 #else
-#define PD(a,b) (((b) << 8) + (a))
+#define PD(a,b) (((b) * POW_2(8)) + (a))
 #endif
 
 /**
@@ -285,9 +286,9 @@ static const int16_t delta_tab_3_5[79]  = { TAB_3_5 };
  * according with endianness of the host machine.
  */
 #if HAVE_BIGENDIAN
-#define PD(a,b) (((a) << 24) + ((a) << 16) + ((b) << 8) + (b))
+#define PD(a,b) (((a) * POW_2(24)) + ((a) * POW_2(16)) + ((b) * POW_2(8)) + (b))
 #else
-#define PD(a,b) (((b) << 24) + ((b) << 16) + ((a) << 8) + (a))
+#define PD(a,b) (((b) * POW_2(24)) + ((b) * POW_2(16)) + ((a) * POW_2(8)) + (a))
 #endif
 
 /*
-- 
2.5.2