Bug 1657087 - Fix fallible behaviour of nsStyleAutoArray and nsStyleImageLayers. r=emilio

Differential Revision: https://phabricator.services.mozilla.com/D85850

layout/style/nsStyleAutoArray.h

@@ -20,11 +20,23 @@ class nsStyleAutoArray {
   // This constructor places a single element in mFirstElement.
   enum WithSingleInitialElement { WITH_SINGLE_INITIAL_ELEMENT };
   explicit nsStyleAutoArray(WithSingleInitialElement) {}
-  nsStyleAutoArray(const nsStyleAutoArray& aOther) { *this = aOther; }
-  nsStyleAutoArray& operator=(const nsStyleAutoArray& aOther) {
+
+  nsStyleAutoArray(const nsStyleAutoArray&) = delete;
+  nsStyleAutoArray& operator=(const nsStyleAutoArray&) = delete;
+
+  nsStyleAutoArray(nsStyleAutoArray&&) = default;
+  nsStyleAutoArray& operator=(nsStyleAutoArray&&) = default;
+
+  bool Assign(const nsStyleAutoArray& aOther, mozilla::fallible_t) {
     mFirstElement = aOther.mFirstElement;
-    mOtherElements = aOther.mOtherElements.Clone();
-    return *this;
+    return mOtherElements.Assign(aOther.mOtherElements, mozilla::fallible);
+  }
+
+  nsStyleAutoArray Clone() const {
+    nsStyleAutoArray res(WITH_SINGLE_INITIAL_ELEMENT);
+    res.mFirstElement = mFirstElement;
+    res.mOtherElements = mOtherElements.Clone();
+    return res;
   }
 
   bool operator==(const nsStyleAutoArray& aOther) const {
@@ -36,13 +48,6 @@ class nsStyleAutoArray {
     return !(*this == aOther);
   }
 
-  nsStyleAutoArray& operator=(nsStyleAutoArray&& aOther) {
-    mFirstElement = aOther.mFirstElement;
-    mOtherElements.SwapElements(aOther.mOtherElements);
-
-    return *this;
-  }
-
   size_t Length() const { return mOtherElements.Length() + 1; }
   const T& operator[](size_t aIndex) const {
     return aIndex == 0 ? mFirstElement : mOtherElements[aIndex - 1];

layout/style/nsStyleStruct.cpp

@@ -1704,25 +1704,8 @@ nsStyleImageLayers::nsStyleImageLayers(const nsStyleImageLayers& aSource)
       mMaskModeCount(aSource.mMaskModeCount),
       mBlendModeCount(aSource.mBlendModeCount),
       mCompositeCount(aSource.mCompositeCount),
-      mLayers(aSource.mLayers)  // deep copy
-{
+      mLayers(aSource.mLayers.Clone()) {
   MOZ_COUNT_CTOR(nsStyleImageLayers);
-  // If the deep copy of mLayers failed, truncate the counts.
-  uint32_t count = mLayers.Length();
-  if (count != aSource.mLayers.Length()) {
-    NS_WARNING("truncating counts due to out-of-memory");
-    mAttachmentCount = std::max(mAttachmentCount, count);
-    mClipCount = std::max(mClipCount, count);
-    mOriginCount = std::max(mOriginCount, count);
-    mRepeatCount = std::max(mRepeatCount, count);
-    mPositionXCount = std::max(mPositionXCount, count);
-    mPositionYCount = std::max(mPositionYCount, count);
-    mImageCount = std::max(mImageCount, count);
-    mSizeCount = std::max(mSizeCount, count);
-    mMaskModeCount = std::max(mMaskModeCount, count);
-    mBlendModeCount = std::max(mBlendModeCount, count);
-    mCompositeCount = std::max(mCompositeCount, count);
-  }
 }
 
 static bool AnyLayerIsElementImage(const nsStyleImageLayers& aLayers) {
@@ -1823,61 +1806,7 @@ nsStyleImageLayers& nsStyleImageLayers::operator=(
   mMaskModeCount = aOther.mMaskModeCount;
   mBlendModeCount = aOther.mBlendModeCount;
   mCompositeCount = aOther.mCompositeCount;
-  mLayers = aOther.mLayers;
-
-  uint32_t count = mLayers.Length();
-  if (count != aOther.mLayers.Length()) {
-    NS_WARNING("truncating counts due to out-of-memory");
-    mAttachmentCount = std::max(mAttachmentCount, count);
-    mClipCount = std::max(mClipCount, count);
-    mOriginCount = std::max(mOriginCount, count);
-    mRepeatCount = std::max(mRepeatCount, count);
-    mPositionXCount = std::max(mPositionXCount, count);
-    mPositionYCount = std::max(mPositionYCount, count);
-    mImageCount = std::max(mImageCount, count);
-    mSizeCount = std::max(mSizeCount, count);
-    mMaskModeCount = std::max(mMaskModeCount, count);
-    mBlendModeCount = std::max(mBlendModeCount, count);
-    mCompositeCount = std::max(mCompositeCount, count);
-  }
-
-  return *this;
-}
-
-nsStyleImageLayers& nsStyleImageLayers::operator=(nsStyleImageLayers&& aOther) {
-  mAttachmentCount = aOther.mAttachmentCount;
-  mClipCount = aOther.mClipCount;
-  mOriginCount = aOther.mOriginCount;
-  mRepeatCount = aOther.mRepeatCount;
-  mPositionXCount = aOther.mPositionXCount;
-  mPositionYCount = aOther.mPositionYCount;
-  mImageCount = aOther.mImageCount;
-  mSizeCount = aOther.mSizeCount;
-  mMaskModeCount = aOther.mMaskModeCount;
-  mBlendModeCount = aOther.mBlendModeCount;
-  mCompositeCount = aOther.mCompositeCount;
-  mLayers = std::move(aOther.mLayers);
-
-  // XXX(Bug 1657087) The OOM check doesn't make sense, probably it was just
-  // copied over from the copy constructor. First, moving cannot fail due to
-  // OOM, second the condition is incorrect. Just because the implementation of
-  // nsStyleAutoArray's move constructor uses swapping, we do not seem to happen
-  // to run into the branch erroneously.
-  uint32_t count = mLayers.Length();
-  if (count != aOther.mLayers.Length()) {
-    NS_WARNING("truncating counts due to out-of-memory");
-    mAttachmentCount = std::max(mAttachmentCount, count);
-    mClipCount = std::max(mClipCount, count);
-    mOriginCount = std::max(mOriginCount, count);
-    mRepeatCount = std::max(mRepeatCount, count);
-    mPositionXCount = std::max(mPositionXCount, count);
-    mPositionYCount = std::max(mPositionYCount, count);
-    mImageCount = std::max(mImageCount, count);
-    mSizeCount = std::max(mSizeCount, count);
-    mMaskModeCount = std::max(mMaskModeCount, count);
-    mBlendModeCount = std::max(mBlendModeCount, count);
-    mCompositeCount = std::max(mCompositeCount, count);
-  }
+  mLayers = aOther.mLayers.Clone();
 
   return *this;
 }
@@ -2287,12 +2216,12 @@ nsStyleDisplay::nsStyleDisplay(const Document& aDocument)
 }
 
 nsStyleDisplay::nsStyleDisplay(const nsStyleDisplay& aSource)
-    : mTransitions(aSource.mTransitions),
+    : mTransitions(aSource.mTransitions.Clone()),
       mTransitionTimingFunctionCount(aSource.mTransitionTimingFunctionCount),
       mTransitionDurationCount(aSource.mTransitionDurationCount),
       mTransitionDelayCount(aSource.mTransitionDelayCount),
       mTransitionPropertyCount(aSource.mTransitionPropertyCount),
-      mAnimations(aSource.mAnimations),
+      mAnimations(aSource.mAnimations.Clone()),
       mAnimationTimingFunctionCount(aSource.mAnimationTimingFunctionCount),
       mAnimationDurationCount(aSource.mAnimationDurationCount),
       mAnimationDelayCount(aSource.mAnimationDelayCount),

layout/style/nsStyleStruct.h

@@ -316,7 +316,7 @@ struct nsStyleImageLayers {
                               nsStyleImageLayers::LayerType aType) const;
 
   nsStyleImageLayers& operator=(const nsStyleImageLayers& aOther);
-  nsStyleImageLayers& operator=(nsStyleImageLayers&& aOther);
+  nsStyleImageLayers& operator=(nsStyleImageLayers&& aOther) = default;
   bool operator==(const nsStyleImageLayers& aOther) const;
 
   static const nsCSSPropertyID kBackgroundLayerTable[];