Always initialize SkDashPathEffect fields.

SkDashPathEffect is flattened into a hash key as part of the old-and-busted
SkPicture paint deduping code.  If all its fields aren't intialized, this hash
will be based on uninitialized data.  This means the hash won't be
deterministic, and worse, Valgrind and MSAN will make us feel bad.

An alternative to this is to have SkDashPath::CalcDashParameters always
guarantee it writes something to all its output parameters, even when the dash
intervals make no sense.  I like it being dumb and its users defensive, but
could go either way.

BUG=391001
R=reed@google.com, mtklein@google.com

Author: mtklein@chromium.org

Review URL: https://codereview.chromium.org/379813004

1 files changed, 15 insertions, 7 deletions

diff --git a/src/effects/SkDashPathEffect.cpp b/src/effects/SkDashPathEffect.cpp
index 2838b1ff3e..d91e7be977 100644
--- a/src/effects/SkDashPathEffect.cpp
+++ b/src/effects/SkDashPathEffect.cpp
@@ -11,8 +11,11 @@
 #include "SkReadBuffer.h"
 #include "SkWriteBuffer.h"
 
-SkDashPathEffect::SkDashPathEffect(const SkScalar intervals[], int count,
-                                   SkScalar phase) {
+SkDashPathEffect::SkDashPathEffect(const SkScalar intervals[], int count, SkScalar phase)
+        : fPhase(0)
+        , fInitialDashLength(0)
+        , fInitialDashIndex(0)
+        , fIntervalLength(0) {
     SkASSERT(intervals);
     SkASSERT(count > 1 && SkAlign2(count) == count);
 
@@ -24,8 +27,8 @@ SkDashPathEffect::SkDashPathEffect(const SkScalar intervals[], int count,
     }
 
     // set the internal data members
-    SkDashPath::CalcDashParameters(phase, fIntervals, fCount, &fInitialDashLength,
-                                   &fInitialDashIndex, &fIntervalLength, &fPhase);
+    SkDashPath::CalcDashParameters(phase, fIntervals, fCount,
+            &fInitialDashLength, &fInitialDashIndex, &fIntervalLength, &fPhase);
 }
 
 SkDashPathEffect::~SkDashPathEffect() {
@@ -249,7 +252,12 @@ SkFlattenable* SkDashPathEffect::CreateProc(SkReadBuffer& buffer) {
     return SkNEW_ARGS(SkDashPathEffect, (buffer));
 }
 
-SkDashPathEffect::SkDashPathEffect(SkReadBuffer& buffer) : INHERITED(buffer) {
+SkDashPathEffect::SkDashPathEffect(SkReadBuffer& buffer)
+        : INHERITED(buffer)
+        , fPhase(0)
+        , fInitialDashLength(0)
+        , fInitialDashIndex(0)
+        , fIntervalLength(0) {
     bool useOldPic = buffer.isVersionLT(SkReadBuffer::kDashWritesPhaseIntervals_Version);
     if (useOldPic) {
         fInitialDashIndex = buffer.readInt();
@@ -280,7 +288,7 @@ SkDashPathEffect::SkDashPathEffect(SkReadBuffer& buffer) : INHERITED(buffer) {
     } else {
         // set the internal data members, fPhase should have been between 0 and intervalLength
         // when written to buffer so no need to adjust it
-        SkDashPath::CalcDashParameters(fPhase, fIntervals, fCount, &fInitialDashLength,
-                                       &fInitialDashIndex, &fIntervalLength);
+        SkDashPath::CalcDashParameters(fPhase, fIntervals, fCount,
+                &fInitialDashLength, &fInitialDashIndex, &fIntervalLength);
     }
 }