commit 93ca884879e3469b46d32c36deb7b46f2fff1c0c
author caryclark <caryclark@google.com> Fri May 27 05:24:37 2016 -0700
committer Commit bot <commit-bot@chromium.org> Fri May 27 05:24:38 2016 -0700
tree d35e1eeb53f323ffca11054db7e3180fc2fe19e1
parent 64022c1ed2174fb499027f902c25be60ef7c3737

pin before calling acos

Adobe reports some user crashes in acos(). While the cause is
unknown, it's safe and may help stability to pin the input
in case the arguments drifted slightly outside [-1, 1].

R=reed@google.com
BUG=skia:5222
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2006653006

Review-Url: https://codereview.chromium.org/2006653006

src/core/SkGeometry.cpp

diff --git a/src/core/SkGeometry.cpp b/src/core/SkGeometry.cpp
index 7256b9e..5d181a3 100644
--- a/src/core/SkGeometry.cpp
+++ b/src/core/SkGeometry.cpp
@@ -743,7 +743,8 @@
     SkScalar    r;
 
     if (R2MinusQ3 < 0) { // we have 3 real roots
-        SkScalar theta = SkScalarACos(R / SkScalarSqrt(Q3));
+        // the divide/root can, due to finite precisions, be slightly outside of -1...1
+        SkScalar theta = SkScalarACos(SkScalarPin(R / SkScalarSqrt(Q3), -1, 1));
         SkScalar neg2RootQ = -2 * SkScalarSqrt(Q);
 
         r = neg2RootQ * SkScalarCos(theta/3) - adiv3;

src/pathops/SkPathOpsCubic.cpp

diff --git a/src/pathops/SkPathOpsCubic.cpp b/src/pathops/SkPathOpsCubic.cpp
index 6b74fb0..a161e36 100644
--- a/src/pathops/SkPathOpsCubic.cpp
+++ b/src/pathops/SkPathOpsCubic.cpp
@@ -419,7 +419,8 @@
     double r;
     double* roots = s;
     if (R2MinusQ3 < 0) {   // we have 3 real roots
-        double theta = acos(R / sqrt(Q3));
+        // the divide/root can, due to finite precisions, be slightly outside of -1...1
+        double theta = acos(SkTPin(R / sqrt(Q3), -1., 1.));
         double neg2RootQ = -2 * sqrt(Q);
 
         r = neg2RootQ * cos(theta / 3) - adiv3;