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Fix up signed-integer-overflow warnings

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When checking whether a matrix was a pure scale, we subtracted
0x3f800000 from the diagonals; if the diagonal value was already
very negative, we'd underflow. Replace subtraction with XOR.

When dealing with repeating tiled bitmaps, when the bitmap was
very large, we'd multiply an offset by 65535, possibly causing
underflow. Throw in a cast to long (casting to unsigned also
silences the warning and wouldn't involve extension, but I can't
convince myself that it's correct).

BUG=skia:4635
R=mtklein@google.com

Review URL: https://codereview.chromium.org/1504933002
This commit is contained in:
tomhudson 2015-12-07 10:38:05 -08:00 committed by Commit bot
parent d18b1b5adc
commit d5c4265b49
2 changed files with 9 additions and 7 deletions
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14
src/core/SkBitmapProcState_matrixProcs.cpp
View File

@ -95,18 +95,20 @@ static SkBitmapProcState::MatrixProc ClampX_ClampY_Procs[] = {
};
#define MAKENAME(suffix) RepeatX_RepeatY ## suffix
#define TILEX_PROCF(fx, max) SK_USHIFT16(((fx) & 0xFFFF) * ((max) + 1))
#define TILEY_PROCF(fy, max) SK_USHIFT16(((fy) & 0xFFFF) * ((max) + 1))
#define TILEX_LOW_BITS(fx, max) ((((fx) & 0xFFFF) * ((max) + 1) >> 12) & 0xF)
#define TILEY_LOW_BITS(fy, max) ((((fy) & 0xFFFF) * ((max) + 1) >> 12) & 0xF)
#define TILEX_PROCF(fx, max) SK_USHIFT16((unsigned)((fx) & 0xFFFF) * ((max) + 1))
#define TILEY_PROCF(fy, max) SK_USHIFT16((unsigned)((fy) & 0xFFFF) * ((max) + 1))
#define TILEX_LOW_BITS(fx, max) (((unsigned)((fx) & 0xFFFF) * ((max) + 1) >> 12) & 0xF)
#define TILEY_LOW_BITS(fy, max) (((unsigned)((fy) & 0xFFFF) * ((max) + 1) >> 12) & 0xF)
#include "SkBitmapProcState_matrix.h"
struct RepeatTileProcs {
static unsigned X(const SkBitmapProcState&, SkFixed fx, int max) {
return SK_USHIFT16(((fx) & 0xFFFF) * ((max) + 1));
SkASSERT(max < 65535);
return SK_USHIFT16((unsigned)((fx) & 0xFFFF) * ((max) + 1));
}
static unsigned Y(const SkBitmapProcState&, SkFixed fy, int max) {
return SK_USHIFT16(((fy) & 0xFFFF) * ((max) + 1));
SkASSERT(max < 65535);
return SK_USHIFT16((unsigned)((fy) & 0xFFFF) * ((max) + 1));
}
};

2
src/core/SkMatrix.cpp
View File

@ -156,7 +156,7 @@ uint8_t SkMatrix::computeTypeMask() const {
} else {
// Only test for scale explicitly if not affine, since affine sets the
// scale bit.
if ((m00 - kScalar1Int) | (m11 - kScalar1Int)) {
if ((m00 ^ kScalar1Int) | (m11 ^ kScalar1Int)) {
mask |= kScale_Mask;
}