Bug 525229 - Crash [@ nsHtml5PendingNotification::nsHtml5PendingNotification] when document.writing an external script followed by start tag. r=bnewman, a=beltzner.

2009-10-30 13:47:17 +02:00 · 2009-10-30 13:47:17 +02:00 · d73344abd4
--- a/parser/html/nsHtml5Parser.cpp
+++ b/parser/html/nsHtml5Parser.cpp
@ -602,6 +602,8 @@ nsHtml5Parser::ParseUntilBlocked()
          if (mStreamParser && 
              mReturnToStreamParserPermitted && 
              !mExecutor->IsScriptExecuting()) {
+            mTreeBuilder->flushCharacters();
+            mTreeBuilder->Flush();
            mReturnToStreamParserPermitted = PR_FALSE;
            mStreamParser->ContinueAfterScripts(mTokenizer, 
                                                mTreeBuilder, 
--- a/parser/html/nsHtml5StreamParser.cpp
+++ b/parser/html/nsHtml5StreamParser.cpp
@ -866,7 +866,10 @@ nsHtml5StreamParser::ContinueAfterScripts(nsHtml5Tokenizer* aTokenizer,
      
      mSpeculations.Clear(); // potentially a huge number of destructors 
                             // run here synchronously on the main thread...
-      
+
+      mTreeBuilder->flushCharacters(); // empty the pending buffer
+      mTreeBuilder->ClearOps(); // now get rid of the failed ops
+
      mTreeBuilder->SetOpSink(mExecutor->GetStage());
      mExecutor->StartReadingFromStage();
      mSpeculating = PR_FALSE;
--- a/parser/html/nsHtml5TreeBuilderCppSupplement.h
+++ b/parser/html/nsHtml5TreeBuilderCppSupplement.h
@ -140,10 +140,15 @@ nsIContent**
 nsHtml5TreeBuilder::createElement(PRInt32 aNamespace, nsIAtom* aName, nsHtml5HtmlAttributes* aAttributes)
 {
  NS_PRECONDITION(aAttributes, "Got null attributes.");
+  NS_PRECONDITION(aName, "Got null name.");
+  NS_PRECONDITION(aNamespace == kNameSpaceID_XHTML || 
+                  aNamespace == kNameSpaceID_SVG || 
+                  aNamespace == kNameSpaceID_MathML,
+                  "Bogus namespace.");

  nsIContent** content = AllocateContentHandle();
  nsHtml5TreeOperation* treeOp = mOpQueue.AppendElement();
-  // XXX if null, OOM!
+  NS_ASSERTION(treeOp, "Tree op allocation failed.");
  treeOp->Init(aNamespace, aName, aAttributes, content);
  
  // Start wall of code for speculative loading and line numbers
@ -158,7 +163,7 @@ nsHtml5TreeBuilder::createElement(PRInt32 aNamespace, nsIAtom* aName, nsHtml5Htm
          }
        } else if (nsHtml5Atoms::script == aName) {
          nsHtml5TreeOperation* treeOp = mOpQueue.AppendElement();
-          // XXX if null, OOM!
+          NS_ASSERTION(treeOp, "Tree op allocation failed.");
          treeOp->Init(eTreeOpSetScriptLineNumber, content, tokenizer->getLineNumber());

          nsString* url = aAttributes->getValue(nsHtml5AttributeName::ATTR_SRC);
@ -190,7 +195,7 @@ nsHtml5TreeBuilder::createElement(PRInt32 aNamespace, nsIAtom* aName, nsHtml5Htm
          }
        } else if (nsHtml5Atoms::style == aName) {
          nsHtml5TreeOperation* treeOp = mOpQueue.AppendElement();
-          // XXX if null, OOM!
+          NS_ASSERTION(treeOp, "Tree op allocation failed.");
          treeOp->Init(eTreeOpSetStyleLineNumber, content, tokenizer->getLineNumber());
        }
        break;
@ -202,7 +207,7 @@ nsHtml5TreeBuilder::createElement(PRInt32 aNamespace, nsIAtom* aName, nsHtml5Htm
          }
        } else if (nsHtml5Atoms::script == aName) {
          nsHtml5TreeOperation* treeOp = mOpQueue.AppendElement();
-          // XXX if null, OOM!
+          NS_ASSERTION(treeOp, "Tree op allocation failed.");
          treeOp->Init(eTreeOpSetScriptLineNumber, content, tokenizer->getLineNumber());

          nsString* url = aAttributes->getValue(nsHtml5AttributeName::ATTR_XLINK_HREF);
@ -215,7 +220,7 @@ nsHtml5TreeBuilder::createElement(PRInt32 aNamespace, nsIAtom* aName, nsHtml5Htm
          }
        } else if (nsHtml5Atoms::style == aName) {
          nsHtml5TreeOperation* treeOp = mOpQueue.AppendElement();
-          // XXX if null, OOM!
+          NS_ASSERTION(treeOp, "Tree op allocation failed.");
          treeOp->Init(eTreeOpSetStyleLineNumber, content, tokenizer->getLineNumber());

          nsString* url = aAttributes->getValue(nsHtml5AttributeName::ATTR_XLINK_HREF);
@ -231,11 +236,11 @@ nsHtml5TreeBuilder::createElement(PRInt32 aNamespace, nsIAtom* aName, nsHtml5Htm
    // No speculative loader--just line numbers
    if (nsHtml5Atoms::style == aName) {
      nsHtml5TreeOperation* treeOp = mOpQueue.AppendElement();
-      // XXX if null, OOM!
+      NS_ASSERTION(treeOp, "Tree op allocation failed.");
      treeOp->Init(eTreeOpSetStyleLineNumber, content, tokenizer->getLineNumber());
    } else if (nsHtml5Atoms::script == aName) {
      nsHtml5TreeOperation* treeOp = mOpQueue.AppendElement();
-      // XXX if null, OOM!
+      NS_ASSERTION(treeOp, "Tree op allocation failed.");
      treeOp->Init(eTreeOpSetScriptLineNumber, content, tokenizer->getLineNumber());
    }
  }
@ -251,7 +256,7 @@ nsHtml5TreeBuilder::createElement(PRInt32 aNamespace, nsIAtom* aName, nsHtml5Htm
  nsIContent** content = createElement(aNamespace, aName, aAttributes);
  if (aFormElement) {
    nsHtml5TreeOperation* treeOp = mOpQueue.AppendElement();
-    // XXX if null, OOM!
+    NS_ASSERTION(treeOp, "Tree op allocation failed.");
    treeOp->Init(eTreeOpSetFormElement, content, aFormElement);
  }
  return content;
@ -262,7 +267,7 @@ nsHtml5TreeBuilder::createHtmlElementSetAsRoot(nsHtml5HtmlAttributes* aAttribute
 {
  nsIContent** content = createElement(kNameSpaceID_XHTML, nsHtml5Atoms::html, aAttributes);
  nsHtml5TreeOperation* treeOp = mOpQueue.AppendElement();
-  // XXX if null, OOM!
+  NS_ASSERTION(treeOp, "Tree op allocation failed.");
  treeOp->Init(eTreeOpAppendToDocument, content);
  return content;
 }
@ -270,126 +275,154 @@ nsHtml5TreeBuilder::createHtmlElementSetAsRoot(nsHtml5HtmlAttributes* aAttribute
 void
 nsHtml5TreeBuilder::detachFromParent(nsIContent** aElement)
 {
+  NS_PRECONDITION(aElement, "Null element");
+
  nsHtml5TreeOperation* treeOp = mOpQueue.AppendElement();
-  // XXX if null, OOM!
+  NS_ASSERTION(treeOp, "Tree op allocation failed.");
  treeOp->Init(eTreeOpDetach, aElement);
 }

 void
 nsHtml5TreeBuilder::appendElement(nsIContent** aChild, nsIContent** aParent)
 {
+  NS_PRECONDITION(aChild, "Null child");
+  NS_PRECONDITION(aParent, "Null parent");
+
  nsHtml5TreeOperation* treeOp = mOpQueue.AppendElement();
-  // XXX if null, OOM!
+  NS_ASSERTION(treeOp, "Tree op allocation failed.");
  treeOp->Init(eTreeOpAppend, aChild, aParent);
 }

 void
 nsHtml5TreeBuilder::appendChildrenToNewParent(nsIContent** aOldParent, nsIContent** aNewParent)
 {
+  NS_PRECONDITION(aOldParent, "Null old parent");
+  NS_PRECONDITION(aNewParent, "Null new parent");
+
  nsHtml5TreeOperation* treeOp = mOpQueue.AppendElement();
-  // XXX if null, OOM!
+  NS_ASSERTION(treeOp, "Tree op allocation failed.");
  treeOp->Init(eTreeOpAppendChildrenToNewParent, aOldParent, aNewParent);
 }

 void
 nsHtml5TreeBuilder::insertFosterParentedCharacters(PRUnichar* aBuffer, PRInt32 aStart, PRInt32 aLength, nsIContent** aTable, nsIContent** aStackParent)
 {
+  NS_PRECONDITION(aBuffer, "Null buffer");
+  NS_PRECONDITION(aTable, "Null table");
+  NS_PRECONDITION(aStackParent, "Null stack parent");
+
  PRUnichar* bufferCopy = new PRUnichar[aLength];
  memcpy(bufferCopy, aBuffer, aLength * sizeof(PRUnichar));
  
  nsIContent** text = AllocateContentHandle();

  nsHtml5TreeOperation* treeOp = mOpQueue.AppendElement();
-  // XXX if null, OOM!
+  NS_ASSERTION(treeOp, "Tree op allocation failed.");
  treeOp->Init(eTreeOpCreateTextNode, bufferCopy, aLength, text);

  treeOp = mOpQueue.AppendElement();
-  // XXX if null, OOM!
+  NS_ASSERTION(treeOp, "Tree op allocation failed.");
  treeOp->Init(eTreeOpFosterParent, text, aStackParent, aTable);
 }

 void
 nsHtml5TreeBuilder::insertFosterParentedChild(nsIContent** aChild, nsIContent** aTable, nsIContent** aStackParent)
 {
+  NS_PRECONDITION(aChild, "Null child");
+  NS_PRECONDITION(aTable, "Null table");
+  NS_PRECONDITION(aStackParent, "Null stack parent");
+
  nsHtml5TreeOperation* treeOp = mOpQueue.AppendElement();
-  // XXX if null, OOM!
+  NS_ASSERTION(treeOp, "Tree op allocation failed.");
  treeOp->Init(eTreeOpFosterParent, aChild, aStackParent, aTable);
 }

 void
 nsHtml5TreeBuilder::appendCharacters(nsIContent** aParent, PRUnichar* aBuffer, PRInt32 aStart, PRInt32 aLength)
 {
+  NS_PRECONDITION(aBuffer, "Null buffer");
+  NS_PRECONDITION(aParent, "Null parent");
+
  PRUnichar* bufferCopy = new PRUnichar[aLength];
  memcpy(bufferCopy, aBuffer, aLength * sizeof(PRUnichar));
  
  nsIContent** text = AllocateContentHandle();

  nsHtml5TreeOperation* treeOp = mOpQueue.AppendElement();
-  // XXX if null, OOM!
+  NS_ASSERTION(treeOp, "Tree op allocation failed.");
  treeOp->Init(eTreeOpCreateTextNode, bufferCopy, aLength, text);

  treeOp = mOpQueue.AppendElement();
-  // XXX if null, OOM!
+  NS_ASSERTION(treeOp, "Tree op allocation failed.");
  treeOp->Init(eTreeOpAppend, text, aParent);
 }

 void
 nsHtml5TreeBuilder::appendComment(nsIContent** aParent, PRUnichar* aBuffer, PRInt32 aStart, PRInt32 aLength)
 {
+  NS_PRECONDITION(aBuffer, "Null buffer");
+  NS_PRECONDITION(aParent, "Null parent");
+
  PRUnichar* bufferCopy = new PRUnichar[aLength];
  memcpy(bufferCopy, aBuffer, aLength * sizeof(PRUnichar));
  
  nsIContent** comment = AllocateContentHandle();

  nsHtml5TreeOperation* treeOp = mOpQueue.AppendElement();
-  // XXX if null, OOM!
+  NS_ASSERTION(treeOp, "Tree op allocation failed.");
  treeOp->Init(eTreeOpCreateComment, bufferCopy, aLength, comment);

  treeOp = mOpQueue.AppendElement();
-  // XXX if null, OOM!
+  NS_ASSERTION(treeOp, "Tree op allocation failed.");
  treeOp->Init(eTreeOpAppend, comment, aParent);
 }

 void
 nsHtml5TreeBuilder::appendCommentToDocument(PRUnichar* aBuffer, PRInt32 aStart, PRInt32 aLength)
 {
+  NS_PRECONDITION(aBuffer, "Null buffer");
+
  PRUnichar* bufferCopy = new PRUnichar[aLength];
  memcpy(bufferCopy, aBuffer, aLength * sizeof(PRUnichar));
  
  nsIContent** comment = AllocateContentHandle();

  nsHtml5TreeOperation* treeOp = mOpQueue.AppendElement();
-  // XXX if null, OOM!
+  NS_ASSERTION(treeOp, "Tree op allocation failed.");
  treeOp->Init(eTreeOpCreateComment, bufferCopy, aLength, comment);

  treeOp = mOpQueue.AppendElement();
-  // XXX if null, OOM!
+  NS_ASSERTION(treeOp, "Tree op allocation failed.");
  treeOp->Init(eTreeOpAppendToDocument, comment);
 }

 void
 nsHtml5TreeBuilder::addAttributesToElement(nsIContent** aElement, nsHtml5HtmlAttributes* aAttributes)
 {
+  NS_PRECONDITION(aElement, "Null element");
+  NS_PRECONDITION(aAttributes, "Null attributes");
+
  if (aAttributes == nsHtml5HtmlAttributes::EMPTY_ATTRIBUTES) {
    return;
  }
  nsHtml5TreeOperation* treeOp = mOpQueue.AppendElement();
-  // XXX if null, OOM!
+  NS_ASSERTION(treeOp, "Tree op allocation failed.");
  treeOp->Init(aElement, aAttributes);
 }

 void
-nsHtml5TreeBuilder::markMalformedIfScript(nsIContent** elt)
+nsHtml5TreeBuilder::markMalformedIfScript(nsIContent** aElement)
 {
+  NS_PRECONDITION(aElement, "Null element");
+
  nsHtml5TreeOperation* treeOp = mOpQueue.AppendElement();
-  // XXX if null, OOM!
-  treeOp->Init(eTreeOpMarkMalformedIfScript, elt);
+  NS_ASSERTION(treeOp, "Tree op allocation failed.");
+  treeOp->Init(eTreeOpMarkMalformedIfScript, aElement);
 }

 void
 nsHtml5TreeBuilder::start(PRBool fragment)
 {
-  // XXX check that timer creation didn't fail in constructor
 #ifdef DEBUG
  mActive = PR_TRUE;
 #endif
@ -407,14 +440,16 @@ nsHtml5TreeBuilder::end()
 void
 nsHtml5TreeBuilder::appendDoctypeToDocument(nsIAtom* aName, nsString* aPublicId, nsString* aSystemId)
 {
+  NS_PRECONDITION(aName, "Null name");
+
  nsIContent** content = AllocateContentHandle();

  nsHtml5TreeOperation* treeOp = mOpQueue.AppendElement();
-  // XXX if null, OOM!
+  NS_ASSERTION(treeOp, "Tree op allocation failed.");
  treeOp->Init(aName, *aPublicId, *aSystemId, content);
  
  treeOp = mOpQueue.AppendElement();
-  // XXX if null, OOM!
+  NS_ASSERTION(treeOp, "Tree op allocation failed.");
  treeOp->Init(eTreeOpAppendToDocument, content);
  // nsXMLContentSink can flush here, but what's the point?
  // It can also interrupt here, but we can't.
@ -430,7 +465,7 @@ nsHtml5TreeBuilder::elementPushed(PRInt32 aNamespace, nsIAtom* aName, nsIContent
  if (aNamespace == kNameSpaceID_XHTML) {
    if (aName == nsHtml5Atoms::html) {
      nsHtml5TreeOperation* treeOp = mOpQueue.AppendElement();
-      // XXX if null, OOM!
+      NS_ASSERTION(treeOp, "Tree op allocation failed.");
      treeOp->Init(eTreeOpProcessOfflineManifest, aElement);
      return;
    }
@ -450,19 +485,19 @@ nsHtml5TreeBuilder::elementPopped(PRInt32 aNamespace, nsIAtom* aName, nsIContent
  if (aName == nsHtml5Atoms::script) {
    requestSuspension();
    nsHtml5TreeOperation* treeOp = mOpQueue.AppendElement();
-    // XXX if null, OOM!
+    NS_ASSERTION(treeOp, "Tree op allocation failed.");
    treeOp->InitScript(aElement);
    return;
  }
  if (aName == nsHtml5Atoms::title) {
    nsHtml5TreeOperation* treeOp = mOpQueue.AppendElement();
-    // XXX if null, OOM!
+    NS_ASSERTION(treeOp, "Tree op allocation failed.");
    treeOp->Init(eTreeOpDoneAddingChildren, aElement);
    return;
  }
  if (aName == nsHtml5Atoms::style || (aNamespace == kNameSpaceID_XHTML && aName == nsHtml5Atoms::link)) {
    nsHtml5TreeOperation* treeOp = mOpQueue.AppendElement();
-    // XXX if null, OOM!
+    NS_ASSERTION(treeOp, "Tree op allocation failed.");
    treeOp->Init(eTreeOpUpdateStyleSheet, aElement);
    return;
  }
@ -500,33 +535,33 @@ nsHtml5TreeBuilder::elementPopped(PRInt32 aNamespace, nsIAtom* aName, nsIContent
        aName == nsHtml5Atoms::object ||
        aName == nsHtml5Atoms::applet) {
    nsHtml5TreeOperation* treeOp = mOpQueue.AppendElement();
-    // XXX if null, OOM!
+    NS_ASSERTION(treeOp, "Tree op allocation failed.");
    treeOp->Init(eTreeOpDoneAddingChildren, aElement);
    return;
  }
  if (aName == nsHtml5Atoms::input ||
      aName == nsHtml5Atoms::button) {
    nsHtml5TreeOperation* treeOp = mOpQueue.AppendElement();
-    // XXX if null, OOM!
+    NS_ASSERTION(treeOp, "Tree op allocation failed.");
    treeOp->Init(eTreeOpDoneCreatingElement, aElement);
    return;
  }
  if (aName == nsHtml5Atoms::base) {
    nsHtml5TreeOperation* treeOp = mOpQueue.AppendElement();
-    // XXX if null, OOM!
+    NS_ASSERTION(treeOp, "Tree op allocation failed.");
    treeOp->Init(eTreeOpProcessBase, aElement);
    return;
  }
  if (aName == nsHtml5Atoms::meta) {
    nsHtml5TreeOperation* treeOp = mOpQueue.AppendElement();
-    // XXX if null, OOM!
+    NS_ASSERTION(treeOp, "Tree op allocation failed.");
    treeOp->Init(eTreeOpProcessMeta, aElement);
    return;
  }
  if (aName == nsHtml5Atoms::head) {
    nsHtml5TreeOperation* treeOp = mOpQueue.AppendElement();
-    // XXX if null, OOM!
-    treeOp->Init(eTreeOpStartLayout, nsnull);
+    NS_ASSERTION(treeOp, "Tree op allocation failed.");
+    treeOp->Init(eTreeOpStartLayout);
    return;
  }
  return;
@ -555,6 +590,9 @@ nsHtml5TreeBuilder::AllocateContentHandle()
    mHandles = new nsIContent*[NS_HTML5_TREE_BUILDER_HANDLE_ARRAY_LENGTH];
    mHandlesUsed = 0;
  }
+#ifdef DEBUG
+  mHandles[mHandlesUsed] = (nsIContent*)0xC0DEDBAD;
+#endif
  return &mHandles[mHandlesUsed++];
 }

@ -584,7 +622,7 @@ void
 nsHtml5TreeBuilder::SetDocumentCharset(nsACString& aCharset)
 {
  nsHtml5TreeOperation* treeOp = mOpQueue.AppendElement();
-  // XXX if null, OOM!
+  NS_ASSERTION(treeOp, "Tree op allocation failed.");
  treeOp->Init(eTreeOpSetDocumentCharset, aCharset);  
 }

@ -598,7 +636,7 @@ nsHtml5TreeBuilder::StreamEnded()
  // innerHTML content.
  if (!fragment) {
    nsHtml5TreeOperation* treeOp = mOpQueue.AppendElement();
-    // XXX if null, OOM!
+    NS_ASSERTION(treeOp, "Tree op allocation failed.");
    treeOp->Init(eTreeOpStreamEnded);
  }
 }
@ -607,7 +645,7 @@ void
 nsHtml5TreeBuilder::NeedsCharsetSwitchTo(const nsACString& aCharset)
 {
  nsHtml5TreeOperation* treeOp = mOpQueue.AppendElement();
-  // XXX if null, OOM!
+  NS_ASSERTION(treeOp, "Tree op allocation failed.");
  treeOp->Init(eTreeOpNeedsCharsetSwitchTo, aCharset);  
 }

@ -635,6 +673,6 @@ void
 nsHtml5TreeBuilder::documentMode(nsHtml5DocumentMode m)
 {
  nsHtml5TreeOperation* treeOp = mOpQueue.AppendElement();
-  // XXX if null, OOM!
+  NS_ASSERTION(treeOp, "Tree op allocation failed.");
  treeOp->Init(m);
 }
--- a/parser/html/nsHtml5TreeBuilderHSupplement.h
+++ b/parser/html/nsHtml5TreeBuilderHSupplement.h
@ -68,6 +68,10 @@
    void SetOpSink(nsAHtml5TreeOpSink* aOpSink) {
      mOpSink = aOpSink;
    }
+
+    void ClearOps() {
+      mOpQueue.Clear();
+    }
    
    void SetSpeculativeLoaderWithDocument(nsIDocument* aDocument);

--- a/parser/html/nsHtml5TreeOperation.h
+++ b/parser/html/nsHtml5TreeOperation.h
@ -117,6 +117,7 @@ class nsHtml5TreeOperation {
    inline void Init(eHtml5TreeOperation aOpCode, nsIContent** aNode) {
      NS_PRECONDITION(mOpCode == eTreeOpUninitialized,
        "Op code must be uninitialized when initializing.");
+      NS_PRECONDITION(aNode, "Initialized tree op with null node.");
      mOpCode = aOpCode;
      mOne.node = aNode;
    }
@ -126,6 +127,8 @@ class nsHtml5TreeOperation {
                     nsIContent** aParent) {
      NS_PRECONDITION(mOpCode == eTreeOpUninitialized,
        "Op code must be uninitialized when initializing.");
+      NS_PRECONDITION(aNode, "Initialized tree op with null node.");
+      NS_PRECONDITION(aParent, "Initialized tree op with null parent.");
      mOpCode = aOpCode;
      mOne.node = aNode;
      mTwo.node = aParent;
@ -137,6 +140,9 @@ class nsHtml5TreeOperation {
                     nsIContent** aTable) {
      NS_PRECONDITION(mOpCode == eTreeOpUninitialized,
        "Op code must be uninitialized when initializing.");
+      NS_PRECONDITION(aNode, "Initialized tree op with null node.");
+      NS_PRECONDITION(aParent, "Initialized tree op with null parent.");
+      NS_PRECONDITION(aTable, "Initialized tree op with null table.");
      mOpCode = aOpCode;
      mOne.node = aNode;
      mTwo.node = aParent;
@ -153,6 +159,7 @@ class nsHtml5TreeOperation {
    inline void InitScript(nsIContent** aNode) {
      NS_PRECONDITION(mOpCode == eTreeOpUninitialized,
        "Op code must be uninitialized when initializing.");
+      NS_PRECONDITION(aNode, "Initialized tree op with null node.");
      mOpCode = eTreeOpRunScript;
      mOne.node = aNode;
      mTwo.state = nsnull;
@ -164,6 +171,8 @@ class nsHtml5TreeOperation {
                     nsIContent** aTarget) {
      NS_PRECONDITION(mOpCode == eTreeOpUninitialized,
        "Op code must be uninitialized when initializing.");
+      NS_PRECONDITION(aName, "Initialized tree op with null name.");
+      NS_PRECONDITION(aTarget, "Initialized tree op with null target node.");
      mOpCode = eTreeOpCreateElement;
      mInt = aNamespace;
      mOne.node = aTarget;
@ -181,6 +190,7 @@ class nsHtml5TreeOperation {
                     nsIContent** aTarget) {
      NS_PRECONDITION(mOpCode == eTreeOpUninitialized,
        "Op code must be uninitialized when initializing.");
+      NS_PRECONDITION(aBuffer, "Initialized tree op with null buffer.");
      mOpCode = aOpCode;
      mOne.node = aTarget;
      mTwo.unicharPtr = aBuffer;
@ -191,6 +201,7 @@ class nsHtml5TreeOperation {
                     nsHtml5HtmlAttributes* aAttributes) {
      NS_PRECONDITION(mOpCode == eTreeOpUninitialized,
        "Op code must be uninitialized when initializing.");
+      NS_PRECONDITION(aElement, "Initialized tree op with null element.");
      mOpCode = eTreeOpAddAttributes;
      mOne.node = aElement;
      mTwo.attributes = aAttributes;
@ -228,7 +239,7 @@ class nsHtml5TreeOperation {
                     PRInt32 aInt) {
      NS_PRECONDITION(mOpCode == eTreeOpUninitialized,
        "Op code must be uninitialized when initializing.");
-
+      NS_PRECONDITION(aNode, "Initialized tree op with null node.");
      mOpCode = aOpCode;
      mOne.node = aNode;
      mInt = aInt;
@ -241,6 +252,7 @@ class nsHtml5TreeOperation {
    inline void SetSnapshot(nsAHtml5TreeBuilderState* aSnapshot, PRInt32 aLine) {
      NS_ASSERTION(IsRunScript(), 
        "Setting a snapshot for a tree operation other than eTreeOpRunScript!");
+      NS_PRECONDITION(aSnapshot, "Initialized tree op with null snapshot.");
      mTwo.state = aSnapshot;
      mInt = aLine;
    }