Bug 1295192 - part 1 - remove CPP_THROW_NEW on layout struct operator new overloads that forward to nsPresShell::AllocateByObjectID; r=dholbert

Structs in our style system use an arena-style allocation system,
managed by the presshell to which they belong.  All of the relevant
overloads that forward allocation requests to the presshell declare
themselves as CPP_THROW_NEW, which indicates that they do not throw
exceptions.  The C++ specification states that operator new overloads
that declare themselves to not throw exceptions require a null check on
their return value.  However, the relevant presshell allocation method,
AllocateByObjectID, is infallible and will never return a null pointer.

The callers of all of these methods are therefore doing useless
(compiler-generated) null checks.  Let's get rid of those useless checks
by removing the CPP_THROW_NEW annotations.  This change declares these
methods will return non-null pointers and throw exceptions in case of
errors--but as we don't use exceptions, and AllocateByObjectID will
abort on OOM, everything works out OK.

layout/generic/nsFrameList.cpp

@@ -25,7 +25,7 @@ const AlignedFrameListBytes gEmptyFrameListBytes = { 0 };
 } // namespace mozilla
 
 void*
-nsFrameList::operator new(size_t sz, nsIPresShell* aPresShell) CPP_THROW_NEW
+nsFrameList::operator new(size_t sz, nsIPresShell* aPresShell)
 {
   return aPresShell->AllocateByObjectID(eArenaObjectID_nsFrameList, sz);
 }

layout/generic/nsFrameList.h

@@ -76,7 +76,7 @@ public:
   /**
    * Infallibly allocate a nsFrameList from the shell arena.
    */
-  void* operator new(size_t sz, nsIPresShell* aPresShell) CPP_THROW_NEW;
+  void* operator new(size_t sz, nsIPresShell* aPresShell);
 
   /**
    * Deallocate this list that was allocated from the shell arena.

layout/generic/nsLineBox.cpp

@@ -147,7 +147,7 @@ nsLineBox::NoteFramesMovedFrom(nsLineBox* aFromLine)
 }
 
 void*
-nsLineBox::operator new(size_t sz, nsIPresShell* aPresShell) CPP_THROW_NEW
+nsLineBox::operator new(size_t sz, nsIPresShell* aPresShell)
 {
   return aPresShell->AllocateByObjectID(eArenaObjectID_nsLineBox, sz);
 }

layout/generic/nsLineBox.h

@@ -208,7 +208,7 @@ private:
   
   // Infallible overloaded new operator. Uses an arena (which comes from the
   // presShell) to perform the allocation.
-  void* operator new(size_t sz, nsIPresShell* aPresShell) CPP_THROW_NEW;
+  void* operator new(size_t sz, nsIPresShell* aPresShell);
   void operator delete(void* aPtr, size_t sz) = delete;
 
 public:

layout/style/CounterStyleManager.cpp

@@ -980,7 +980,7 @@ public:
   NS_IMETHOD_(MozExternalRefCountType) AddRef() override;
   NS_IMETHOD_(MozExternalRefCountType) Release() override;
 
-  void* operator new(size_t sz, nsPresContext* aPresContext) CPP_THROW_NEW
+  void* operator new(size_t sz, nsPresContext* aPresContext)
   {
     return aPresContext->PresShell()->AllocateByObjectID(
         eArenaObjectID_DependentBuiltinCounterStyle, sz);
@@ -1101,7 +1101,7 @@ public:
   NS_IMETHOD_(MozExternalRefCountType) AddRef() override;
   NS_IMETHOD_(MozExternalRefCountType) Release() override;
 
-  void* operator new(size_t sz, nsPresContext* aPresContext) CPP_THROW_NEW
+  void* operator new(size_t sz, nsPresContext* aPresContext)
   {
     return aPresContext->PresShell()->AllocateByObjectID(
         eArenaObjectID_CustomCounterStyle, sz);

layout/style/nsRuleNode.cpp

@@ -1520,7 +1520,7 @@ SetFactor(const nsCSSValue& aValue, float& aField, RuleNodeCacheConditions& aCon
 }
 
 void*
-nsRuleNode::operator new(size_t sz, nsPresContext* aPresContext) CPP_THROW_NEW
+nsRuleNode::operator new(size_t sz, nsPresContext* aPresContext)
 {
   // Check the recycle list first.
   return aPresContext->PresShell()->AllocateByObjectID(eArenaObjectID_nsRuleNode, sz);

layout/style/nsRuleNode.h

@@ -36,7 +36,7 @@ struct nsInheritedStyleData
                        nsStyleStructID_Inherited_Start,
                        nsStyleStructID_Inherited_Count> mStyleStructs;
 
-  void* operator new(size_t sz, nsPresContext* aContext) CPP_THROW_NEW {
+  void* operator new(size_t sz, nsPresContext* aContext) {
     return aContext->PresShell()->
       AllocateByObjectID(mozilla::eArenaObjectID_nsInheritedStyleData, sz);
   }
@@ -84,7 +84,7 @@ struct nsResetStyleData
     }
   }
 
-  void* operator new(size_t sz, nsPresContext* aContext) CPP_THROW_NEW {
+  void* operator new(size_t sz, nsPresContext* aContext) {
     return aContext->PresShell()->
       AllocateByObjectID(mozilla::eArenaObjectID_nsResetStyleData, sz);
   }
@@ -119,7 +119,7 @@ struct nsConditionalResetStyleData
           Entry* aNext)
       : mConditions(aConditions), mStyleStruct(aStyleStruct), mNext(aNext) {}
 
-    void* operator new(size_t sz, nsPresContext* aContext) CPP_THROW_NEW {
+    void* operator new(size_t sz, nsPresContext* aContext) {
       return aContext->PresShell()->AllocateByObjectID(
           mozilla::eArenaObjectID_nsConditionalResetStyleDataEntry, sz);
     }
@@ -148,7 +148,7 @@ struct nsConditionalResetStyleData
     mConditionalBits = 0;
   }
 
-  void* operator new(size_t sz, nsPresContext* aContext) CPP_THROW_NEW {
+  void* operator new(size_t sz, nsPresContext* aContext) {
     return aContext->PresShell()->AllocateByObjectID(
         mozilla::eArenaObjectID_nsConditionalResetStyleData, sz);
   }
@@ -550,7 +550,7 @@ private:
 
 public:
   // Infallible overloaded new operator that allocates from a presShell arena.
-  void* operator new(size_t sz, nsPresContext* aContext) CPP_THROW_NEW;
+  void* operator new(size_t sz, nsPresContext* aContext);
   void Destroy();
 
   // Implemented in nsStyleSet.h, since it needs to know about nsStyleSet.

layout/style/nsStyleContext.cpp

@@ -1336,7 +1336,7 @@ void nsStyleContext::List(FILE* out, int32_t aIndent, bool aListDescendants)
 // Overloaded new operator. Initializes the memory to 0 and relies on an arena
 // (which comes from the presShell) to perform the allocation.
 void*
-nsStyleContext::operator new(size_t sz, nsPresContext* aPresContext) CPP_THROW_NEW
+nsStyleContext::operator new(size_t sz, nsPresContext* aPresContext)
 {
   // Check the recycle list first.
   return aPresContext->PresShell()->

layout/style/nsStyleContext.h

@@ -81,7 +81,7 @@ public:
                  already_AddRefed<ServoComputedValues> aComputedValues,
                  bool aSkipParentDisplayBasedStyleFixup);
 
-  void* operator new(size_t sz, nsPresContext* aPresContext) CPP_THROW_NEW;
+  void* operator new(size_t sz, nsPresContext* aPresContext);
   void Destroy();
 
   // These two methods are for use by ArenaRefPtr.

layout/style/nsStyleStruct.h

@@ -181,7 +181,7 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleFont
   static already_AddRefed<nsIAtom> GetLanguage(StyleStructContext aPresContext);
 
   void* operator new(size_t sz, nsStyleFont* aSelf) CPP_THROW_NEW { return aSelf; }
-  void* operator new(size_t sz, nsPresContext* aContext) CPP_THROW_NEW {
+  void* operator new(size_t sz, nsPresContext* aContext) {
     return aContext->PresShell()->
       AllocateByObjectID(mozilla::eArenaObjectID_nsStyleFont, sz);
   }
@@ -455,7 +455,7 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleColor
   }
 
   void* operator new(size_t sz, nsStyleColor* aSelf) CPP_THROW_NEW { return aSelf; }
-  void* operator new(size_t sz, nsPresContext* aContext) CPP_THROW_NEW {
+  void* operator new(size_t sz, nsPresContext* aContext) {
     return aContext->PresShell()->
       AllocateByObjectID(mozilla::eArenaObjectID_nsStyleColor, sz);
   }
@@ -824,7 +824,7 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleBackground {
   ~nsStyleBackground();
 
   void* operator new(size_t sz, nsStyleBackground* aSelf) CPP_THROW_NEW { return aSelf; }
-  void* operator new(size_t sz, nsPresContext* aContext) CPP_THROW_NEW {
+  void* operator new(size_t sz, nsPresContext* aContext) {
     return aContext->PresShell()->
       AllocateByObjectID(mozilla::eArenaObjectID_nsStyleBackground, sz);
   }
@@ -884,7 +884,7 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleMargin
   }
 
   void* operator new(size_t sz, nsStyleMargin* aSelf) CPP_THROW_NEW { return aSelf; }
-  void* operator new(size_t sz, nsPresContext* aContext) CPP_THROW_NEW {
+  void* operator new(size_t sz, nsPresContext* aContext) {
     return aContext->PresShell()->
       AllocateByObjectID(mozilla::eArenaObjectID_nsStyleMargin, sz);
   }
@@ -931,7 +931,7 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStylePadding
   }
 
   void* operator new(size_t sz, nsStylePadding* aSelf) CPP_THROW_NEW { return aSelf; }
-  void* operator new(size_t sz, nsPresContext* aContext) CPP_THROW_NEW {
+  void* operator new(size_t sz, nsPresContext* aContext) {
     return aContext->PresShell()->
       AllocateByObjectID(mozilla::eArenaObjectID_nsStylePadding, sz);
   }
@@ -1138,7 +1138,7 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleBorder
   ~nsStyleBorder();
 
   void* operator new(size_t sz, nsStyleBorder* aSelf) CPP_THROW_NEW { return aSelf; }
-  void* operator new(size_t sz, nsPresContext* aContext) CPP_THROW_NEW {
+  void* operator new(size_t sz, nsPresContext* aContext) {
     return aContext->PresShell()->
       AllocateByObjectID(mozilla::eArenaObjectID_nsStyleBorder, sz);
   }
@@ -1371,7 +1371,7 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleOutline
   }
 
   void* operator new(size_t sz, nsStyleOutline* aSelf) CPP_THROW_NEW { return aSelf; }
-  void* operator new(size_t sz, nsPresContext* aContext) CPP_THROW_NEW {
+  void* operator new(size_t sz, nsPresContext* aContext) {
     return aContext->PresShell()->
       AllocateByObjectID(mozilla::eArenaObjectID_nsStyleOutline, sz);
   }
@@ -1484,7 +1484,7 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleList
   ~nsStyleList();
 
   void* operator new(size_t sz, nsStyleList* aSelf) CPP_THROW_NEW { return aSelf; }
-  void* operator new(size_t sz, nsPresContext* aContext) CPP_THROW_NEW {
+  void* operator new(size_t sz, nsPresContext* aContext) {
     return aContext->PresShell()->
       AllocateByObjectID(mozilla::eArenaObjectID_nsStyleList, sz);
   }
@@ -1711,7 +1711,7 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStylePosition
   ~nsStylePosition();
 
   void* operator new(size_t sz, nsStylePosition* aSelf) CPP_THROW_NEW { return aSelf; }
-  void* operator new(size_t sz, nsPresContext* aContext) CPP_THROW_NEW {
+  void* operator new(size_t sz, nsPresContext* aContext) {
     return aContext->PresShell()->
       AllocateByObjectID(mozilla::eArenaObjectID_nsStylePosition, sz);
   }
@@ -1962,7 +1962,7 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleTextReset
   ~nsStyleTextReset();
 
   void* operator new(size_t sz, nsStyleTextReset* aSelf) CPP_THROW_NEW { return aSelf; }
-  void* operator new(size_t sz, nsPresContext* aContext) CPP_THROW_NEW {
+  void* operator new(size_t sz, nsPresContext* aContext) {
     return aContext->PresShell()->
       AllocateByObjectID(mozilla::eArenaObjectID_nsStyleTextReset, sz);
   }
@@ -2049,7 +2049,7 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleText
   ~nsStyleText();
 
   void* operator new(size_t sz, nsStyleText* aSelf) CPP_THROW_NEW { return aSelf; }
-  void* operator new(size_t sz, nsPresContext* aContext) CPP_THROW_NEW {
+  void* operator new(size_t sz, nsPresContext* aContext) {
     return aContext->PresShell()->
       AllocateByObjectID(mozilla::eArenaObjectID_nsStyleText, sz);
   }
@@ -2270,7 +2270,7 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleVisibility
   }
 
   void* operator new(size_t sz, nsStyleVisibility* aSelf) CPP_THROW_NEW { return aSelf; }
-  void* operator new(size_t sz, nsPresContext* aContext) CPP_THROW_NEW {
+  void* operator new(size_t sz, nsPresContext* aContext) {
     return aContext->PresShell()->
       AllocateByObjectID(mozilla::eArenaObjectID_nsStyleVisibility, sz);
   }
@@ -2787,7 +2787,7 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleDisplay
   }
 
   void* operator new(size_t sz, nsStyleDisplay* aSelf) CPP_THROW_NEW { return aSelf; }
-  void* operator new(size_t sz, nsPresContext* aContext) CPP_THROW_NEW {
+  void* operator new(size_t sz, nsPresContext* aContext) {
     return aContext->PresShell()->
       AllocateByObjectID(mozilla::eArenaObjectID_nsStyleDisplay, sz);
   }
@@ -3065,7 +3065,7 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleTable
   ~nsStyleTable();
 
   void* operator new(size_t sz, nsStyleTable* aSelf) CPP_THROW_NEW { return aSelf; }
-  void* operator new(size_t sz, nsPresContext* aContext) CPP_THROW_NEW {
+  void* operator new(size_t sz, nsPresContext* aContext) {
     return aContext->PresShell()->
       AllocateByObjectID(mozilla::eArenaObjectID_nsStyleTable, sz);
   }
@@ -3096,7 +3096,7 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleTableBorder
   ~nsStyleTableBorder();
 
   void* operator new(size_t sz, nsStyleTableBorder* aSelf) CPP_THROW_NEW { return aSelf; }
-  void* operator new(size_t sz, nsPresContext* aContext) CPP_THROW_NEW {
+  void* operator new(size_t sz, nsPresContext* aContext) {
     return aContext->PresShell()->
       AllocateByObjectID(mozilla::eArenaObjectID_nsStyleTableBorder, sz);
   }
@@ -3197,7 +3197,7 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleContent
   ~nsStyleContent();
 
   void* operator new(size_t sz, nsStyleContent* aSelf) CPP_THROW_NEW { return aSelf; }
-  void* operator new(size_t sz, nsPresContext* aContext) CPP_THROW_NEW {
+  void* operator new(size_t sz, nsPresContext* aContext) {
     return aContext->PresShell()->
       AllocateByObjectID(mozilla::eArenaObjectID_nsStyleContent, sz);
   }
@@ -3309,7 +3309,7 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleUIReset
   ~nsStyleUIReset();
 
   void* operator new(size_t sz, nsStyleUIReset* aSelf) CPP_THROW_NEW { return aSelf; }
-  void* operator new(size_t sz, nsPresContext* aContext) CPP_THROW_NEW {
+  void* operator new(size_t sz, nsPresContext* aContext) {
     return aContext->PresShell()->
       AllocateByObjectID(mozilla::eArenaObjectID_nsStyleUIReset, sz);
   }
@@ -3378,7 +3378,7 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleUserInterface
   ~nsStyleUserInterface();
 
   void* operator new(size_t sz, nsStyleUserInterface* aSelf) CPP_THROW_NEW { return aSelf; }
-  void* operator new(size_t sz, nsPresContext* aContext) CPP_THROW_NEW {
+  void* operator new(size_t sz, nsPresContext* aContext) {
     return aContext->PresShell()->
       AllocateByObjectID(mozilla::eArenaObjectID_nsStyleUserInterface, sz);
   }
@@ -3430,7 +3430,7 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleXUL
   ~nsStyleXUL();
 
   void* operator new(size_t sz, nsStyleXUL* aSelf) CPP_THROW_NEW { return aSelf; }
-  void* operator new(size_t sz, nsPresContext* aContext) CPP_THROW_NEW {
+  void* operator new(size_t sz, nsPresContext* aContext) {
     return aContext->PresShell()->
       AllocateByObjectID(mozilla::eArenaObjectID_nsStyleXUL, sz);
   }
@@ -3469,7 +3469,7 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleColumn
   ~nsStyleColumn();
 
   void* operator new(size_t sz, nsStyleColumn* aSelf) CPP_THROW_NEW { return aSelf; }
-  void* operator new(size_t sz, nsPresContext* aContext) CPP_THROW_NEW {
+  void* operator new(size_t sz, nsPresContext* aContext) {
     return aContext->PresShell()->
       AllocateByObjectID(mozilla::eArenaObjectID_nsStyleColumn, sz);
   }
@@ -3567,7 +3567,7 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleSVG
   ~nsStyleSVG();
 
   void* operator new(size_t sz, nsStyleSVG* aSelf) CPP_THROW_NEW { return aSelf; }
-  void* operator new(size_t sz, nsPresContext* aContext) CPP_THROW_NEW {
+  void* operator new(size_t sz, nsPresContext* aContext) {
     return aContext->PresShell()->
       AllocateByObjectID(mozilla::eArenaObjectID_nsStyleSVG, sz);
   }
@@ -3758,7 +3758,7 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleSVGReset
   ~nsStyleSVGReset();
 
   void* operator new(size_t sz, nsStyleSVGReset* aSelf) CPP_THROW_NEW { return aSelf; }
-  void* operator new(size_t sz, nsPresContext* aContext) CPP_THROW_NEW {
+  void* operator new(size_t sz, nsPresContext* aContext) {
     return aContext->PresShell()->
       AllocateByObjectID(mozilla::eArenaObjectID_nsStyleSVGReset, sz);
   }
@@ -3809,7 +3809,7 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleVariables
   ~nsStyleVariables();
 
   void* operator new(size_t sz, nsStyleVariables* aSelf) CPP_THROW_NEW { return aSelf; }
-  void* operator new(size_t sz, nsPresContext* aContext) CPP_THROW_NEW {
+  void* operator new(size_t sz, nsPresContext* aContext) {
     return aContext->PresShell()->
       AllocateByObjectID(mozilla::eArenaObjectID_nsStyleVariables, sz);
   }
@@ -3839,7 +3839,7 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleEffects
   ~nsStyleEffects();
 
   void* operator new(size_t sz, nsStyleEffects* aSelf) CPP_THROW_NEW { return aSelf; }
-  void* operator new(size_t sz, nsPresContext* aContext) CPP_THROW_NEW {
+  void* operator new(size_t sz, nsPresContext* aContext) {
     return aContext->PresShell()->
       AllocateByObjectID(mozilla::eArenaObjectID_nsStyleEffects, sz);
   }