[FFmpeg-cvslog] swscale: Do not shift negative values directly
Luca Barbato
git at videolan.org
Sat Oct 28 20:43:31 EEST 2017
ffmpeg | branch: master | Luca Barbato <lu_zero at gentoo.org> | Sat Apr 15 14:39:45 2017 +0200| [f56fa95cd13f627891a1bfb66bf61b971b9e0238] | committer: Luca Barbato
swscale: Do not shift negative values directly
It is undefined in C as reported:
warning: shifting a negative signed value is undefined
> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=f56fa95cd13f627891a1bfb66bf61b971b9e0238
---
libswscale/output.c | 23 +++++++++++++----------
1 file changed, 13 insertions(+), 10 deletions(-)
diff --git a/libswscale/output.c b/libswscale/output.c
index cfb204300a..07edcfd4cc 100644
--- a/libswscale/output.c
+++ b/libswscale/output.c
@@ -130,6 +130,9 @@ DECLARE_ALIGNED(8, const uint8_t, ff_dither_8x8_220)[8][8] = {
AV_WL16(pos, bias + av_clip_ ## signedness ## 16(val >> shift)); \
}
+// Shifting negative amounts is undefined in C
+#define SHIFT_LEFT(val, shift) ((val) * (1 << (shift)))
+
static av_always_inline void
yuv2plane1_16_c_template(const int32_t *src, uint16_t *dest, int dstW,
int big_endian, int output_bits)
@@ -601,8 +604,8 @@ yuv2rgb48_X_c_template(SwsContext *c, const int16_t *lumFilter,
int j;
int Y1 = -0x40000000;
int Y2 = -0x40000000;
- int U = -128 << 23; // 19
- int V = -128 << 23;
+ int U = SHIFT_LEFT(-128, 23); // 19
+ int V = SHIFT_LEFT(-128, 23);
int R, G, B;
for (j = 0; j < lumFilterSize; j++) {
@@ -663,8 +666,8 @@ yuv2rgb48_2_c_template(SwsContext *c, const int32_t *buf[2],
for (i = 0; i < ((dstW + 1) >> 1); i++) {
int Y1 = (buf0[i * 2] * yalpha1 + buf1[i * 2] * yalpha) >> 14;
int Y2 = (buf0[i * 2 + 1] * yalpha1 + buf1[i * 2 + 1] * yalpha) >> 14;
- int U = (ubuf0[i] * uvalpha1 + ubuf1[i] * uvalpha + (-128 << 23)) >> 14;
- int V = (vbuf0[i] * uvalpha1 + vbuf1[i] * uvalpha + (-128 << 23)) >> 14;
+ int U = (ubuf0[i] * uvalpha1 + ubuf1[i] * uvalpha + SHIFT_LEFT(-128, 23)) >> 14;
+ int V = (vbuf0[i] * uvalpha1 + vbuf1[i] * uvalpha + SHIFT_LEFT(-128, 23)) >> 14;
int R, G, B;
Y1 -= c->yuv2rgb_y_offset;
@@ -701,8 +704,8 @@ yuv2rgb48_1_c_template(SwsContext *c, const int32_t *buf0,
for (i = 0; i < ((dstW + 1) >> 1); i++) {
int Y1 = (buf0[i * 2] ) >> 2;
int Y2 = (buf0[i * 2 + 1]) >> 2;
- int U = (ubuf0[i] + (-128 << 11)) >> 2;
- int V = (vbuf0[i] + (-128 << 11)) >> 2;
+ int U = (ubuf0[i] + SHIFT_LEFT(-128, 11)) >> 2;
+ int V = (vbuf0[i] + SHIFT_LEFT(-128, 11)) >> 2;
int R, G, B;
Y1 -= c->yuv2rgb_y_offset;
@@ -729,8 +732,8 @@ yuv2rgb48_1_c_template(SwsContext *c, const int32_t *buf0,
for (i = 0; i < ((dstW + 1) >> 1); i++) {
int Y1 = (buf0[i * 2] ) >> 2;
int Y2 = (buf0[i * 2 + 1]) >> 2;
- int U = (ubuf0[i] + ubuf1[i] + (-128 << 12)) >> 3;
- int V = (vbuf0[i] + vbuf1[i] + (-128 << 12)) >> 3;
+ int U = (ubuf0[i] + ubuf1[i] + SHIFT_LEFT(-128, 12)) >> 3;
+ int V = (vbuf0[i] + vbuf1[i] + SHIFT_LEFT(-128, 12)) >> 3;
int R, G, B;
Y1 -= c->yuv2rgb_y_offset;
@@ -1172,8 +1175,8 @@ yuv2rgb_full_X_c_template(SwsContext *c, const int16_t *lumFilter,
for (i = 0; i < dstW; i++) {
int j;
int Y = 0;
- int U = -128 << 19;
- int V = -128 << 19;
+ int U = SHIFT_LEFT(-128, 19);
+ int V = SHIFT_LEFT(-128, 19);
int R, G, B, A;
for (j = 0; j < lumFilterSize; j++) {
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