Fix uninitialized memory in Sk2DPathEffect

The SkDescriptor checksum calculation for Sk2DPathEffect currently evaluates all the bytes in the embedded SkMatrix.  This includes the type mask, which contains some uninitialized padding.  Changing it to use SkMatrix::flatten() and SkMatrix::unflatten() (as SkGroupShape was doing) avoids the uninitialized data errors.

To test, run SampleApp under valgrind and look for the absence of:

==5490== Conditional jump or move depends on uninitialised value(s)
==5490==    at 0x402ABC9: bcmp (mc_replace_strmem.c:567)
==5490==    by 0x47C55C: SkPaint::descriptorProc(SkMatrix const*, void (*)(SkDescriptor const*, void*), void*, bool) const (SkPaint.cpp:1440)
==5490==    by 0x47C73B: SkPaint::detachCache(SkMatrix const*) const (SkPaint.cpp:1450)
==5490==    by 0x4662A0: SkAutoGlyphCache::SkAutoGlyphCache(SkPaint const&, SkMatrix const*) (SkGlyphCache.h:287)
==5490==    by 0x4628C7: SkDraw::drawText(char const*, unsigned long, float, float, SkPaint const&) const (SkDraw.cpp:1584)
==5490==    by 0x45D2C1: SkDevice::drawText(SkDraw const&, void const*, unsigned long, float, float, SkPaint const&) (SkDevice.cpp:197)
==5490==    by 0x451CA6: SkCanvas::drawText(void const*, unsigned long, float, float, SkPaint const&) (SkCanvas.cpp:1393)
==5490==    by 0x40DB6F: ClockFaceView::onDraw(SkCanvas*) (ClockFaceView.cpp:230)

[reed1, 2011-05-20 18:58:39]

I had just made a similar fix in the pipe code. Good catch.

LGTM

[reed1, 2011-05-20 18:59:46]

http://codereview.appspot.com/4529074/diff/1/src/effects/Sk2DPathEffect.cpp
File src/effects/Sk2DPathEffect.cpp (right):

http://codereview.appspot.com/4529074/diff/1/src/effects/Sk2DPathEffect.cpp#n...
src/effects/Sk2DPathEffect.cpp:94: uint32_t size = buffer.readS32();
maybe add this?

SkASSERT(size <= sizeof(storage));

[Stephen White, 2011-05-20 19:19:23]

On 2011/05/20 18:59:46, reed1 wrote:
> http://codereview.appspot.com/4529074/diff/1/src/effects/Sk2DPathEffect.cpp
> File src/effects/Sk2DPathEffect.cpp (right):
> 
>
http://codereview.appspot.com/4529074/diff/1/src/effects/Sk2DPathEffect.cpp#n...
> src/effects/Sk2DPathEffect.cpp:94: uint32_t size = buffer.readS32();
> maybe add this?
> 
> SkASSERT(size <= sizeof(storage));

Done.  Landed as r1395.  Closing.