[FFmpeg-devel] [PATCH] all: silence clang -Wabsolute-value for unsigned subtractions

[Ganesh Ajjanagadde]

Recent clang (3.5 onwards):
http://llvm.org/releases/3.5.0/tools/clang/docs/ReleaseNotes.html,
http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20141006/116174.html
introduces a new warning -Wabsolute-value.
This patch shuts it up when we do safe unsigned subtractions with no overflow issues.

Signed-off-by: Ganesh Ajjanagadde <gajjanagadde at gmail.com>
---
 libavcodec/flashsv2enc.c | 7 ++++---
 libavfilter/vf_hqx.c     | 7 ++++---
 libavfilter/vf_xbr.c     | 7 ++++---
 3 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/libavcodec/flashsv2enc.c b/libavcodec/flashsv2enc.c
index c2c00f4..42f2062 100644
--- a/libavcodec/flashsv2enc.c
+++ b/libavcodec/flashsv2enc.c
@@ -415,9 +415,10 @@ static inline unsigned int chroma_diff(unsigned int c1, unsigned int c2)
     unsigned int t1 = (c1 & 0x000000ff) + ((c1 & 0x0000ff00) >> 8) + ((c1 & 0x00ff0000) >> 16);
     unsigned int t2 = (c2 & 0x000000ff) + ((c2 & 0x0000ff00) >> 8) + ((c2 & 0x00ff0000) >> 16);
 
-    return abs(t1 - t2) + abs((c1 & 0x000000ff) - (c2 & 0x000000ff)) +
-        abs(((c1 & 0x0000ff00) >> 8) - ((c2 & 0x0000ff00) >> 8)) +
-        abs(((c1 & 0x00ff0000) >> 16) - ((c2 & 0x00ff0000) >> 16));
+    /* cast for -Wabsolute-value in clang 3.5+ */
+    return abs((int) (t1 - t2)) + abs((int) ((c1 & 0x000000ff) - (c2 & 0x000000ff))) +
+        abs((int) (((c1 & 0x0000ff00) >> 8) - ((c2 & 0x0000ff00) >> 8))) +
+        abs((int) (((c1 & 0x00ff0000) >> 16) - ((c2 & 0x00ff0000) >> 16)));
 }
 
 static inline int pixel_color7_fast(Palette * palette, unsigned c15)
diff --git a/libavfilter/vf_hqx.c b/libavfilter/vf_hqx.c
index fa15d9c..75f6181 100644
--- a/libavfilter/vf_hqx.c
+++ b/libavfilter/vf_hqx.c
@@ -65,9 +65,10 @@ static av_always_inline int yuv_diff(uint32_t yuv1, uint32_t yuv2)
 #define YMASK 0xff0000
 #define UMASK 0x00ff00
 #define VMASK 0x0000ff
-    return abs((yuv1 & YMASK) - (yuv2 & YMASK)) > (48 << 16) ||
-           abs((yuv1 & UMASK) - (yuv2 & UMASK)) > ( 7 <<  8) ||
-           abs((yuv1 & VMASK) - (yuv2 & VMASK)) > ( 6 <<  0);
+    /* cast for -Wabsolute-value in clang 3.5+ */
+    return abs((int) ((yuv1 & YMASK) - (yuv2 & YMASK))) > (48 << 16) ||
+           abs((int) ((yuv1 & UMASK) - (yuv2 & UMASK))) > ( 7 <<  8) ||
+           abs((int) ((yuv1 & VMASK) - (yuv2 & VMASK))) > ( 6 <<  0);
 }
 
 /* (c1*w1 + c2*w2) >> s */
diff --git a/libavfilter/vf_xbr.c b/libavfilter/vf_xbr.c
index 38c3b70..8180115 100644
--- a/libavfilter/vf_xbr.c
+++ b/libavfilter/vf_xbr.c
@@ -69,9 +69,10 @@ static uint32_t pixel_diff(uint32_t x, uint32_t y, const uint32_t *r2y)
     uint32_t yuv1 = r2y[x & 0xffffff];
     uint32_t yuv2 = r2y[y & 0xffffff];
 
-    return (abs((yuv1 & YMASK) - (yuv2 & YMASK)) >> 16) +
-           (abs((yuv1 & UMASK) - (yuv2 & UMASK)) >>  8) +
-           abs((yuv1 & VMASK) - (yuv2 & VMASK));
+    /* cast for -Wabsolute-value in clang 3.5+ */
+    return (abs((int) ((yuv1 & YMASK) - (yuv2 & YMASK))) >> 16) +
+           (abs((int) ((yuv1 & UMASK) - (yuv2 & UMASK))) >>  8) +
+            abs((int) ((yuv1 & VMASK) - (yuv2 & VMASK)));
 }
 
 #define ALPHA_BLEND_128_W(a, b) ((((a) & LB_MASK) >> 1) + (((b) & LB_MASK) >> 1))
-- 
2.5.0